FOR PUBLICATION

   UNITED STATES COURT OF APPEALS
        FOR THE NINTH CIRCUIT

PAUL W. PARKER, as Personal                No. 22-35695
Representative of the Estate of Curtis
John Rookaird,                                D.C. No.
                                           2:14-cv-00176-
               Plaintiff-Appellant,             RAJ

 v.

OPINION

BNSF RAILWAY COMPANY, a
Delaware corporation,

               Defendant-Appellee.

       Appeal from the United States District Court
         for the Western District of Washington
        Richard A. Jones, District Judge, Presiding

           Argued and Submitted July 13, 2023
                  Seattle, Washington

                   Filed August 9, 2024

 Before: Susan P. Graber, Ronald M. Gould, and Richard
                A. Paez, Circuit Judges.

                 Opinion by Judge Gould;
                 Dissent by Judge Graber
2               PARKER V. BNSF RAILWAY COMPANY


                          SUMMARY *


                 Federal Railroad Safety Act

    The panel affirmed in part and vacated in part the district
court’s judgment in favor of BNSF Railway Company in an
action brought under the anti-retaliation provision of the
Federal Railroad Safety Act by Curtis Rookaird through his
estate representative Paul Parker.
    After a jury found in Rookaird’s favor, this court vacated
the verdict and remanded for the district court to reconsider
its partial summary judgment for Rookaird on the issue
whether his performing an air-brake test had contributed to
BNSF’s decision to terminate him. On remand, the district
court conducted a bench trial on the issue and decided in
BNSF’s favor. The district court found that BNSF had
conceded that Rookaird’s refusal to stop performing the air-
brake test contributed to its decision to discharge him, but
the district court nonetheless concluded that BNSF was
entitled to an affirmative defense by showing that the air-
brake test “contributed very little” to its decision.
    The panel affirmed the district court’s evidentiary
rulings, concluding that the district court did not abuse its
discretion in excluding certain testimony designations and
admitting BNSF’s comparator evidence.
   The panel concluded, however, that the district court’s
application of the Federal Railroad Safety Act did not
comply with the text of the statute, which prohibits the

*
 This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
              PARKER V. BNSF RAILWAY COMPANY                3


discriminatory discharge of an employee due even “in part”
to the employee’s refusal to violate or assist in violating a
railroad safety law, rule, or regulation. Nor was the district
court’s conclusion consistent with relevant case law. The
panel held that BNSF needed to demonstrate by clear and
convincing evidence not merely that it could have fired
Rookaird absent his engaging in the protected activity, but
rather that it would have fired Rookaird. The panel vacated
the district court’s judgment and remanded for the district
court to consider whether BNSF met its burden to prove that
the company would have terminated Rookaird absent his
refusal to stop performing the air-brake test, given that the
test could not contribute even in part to a termination
decision.
    Dissenting, Judge Graber wrote that the majority
misread both the relevant statute and the district court’s
decision. She wrote that the record amply supported the
district court’s finding that BNSF proved its affirmative
defense by presenting clear and convincing evidence that it
would have fired Rookaird anyway, even if he had not
engaged in the protected activity of testing the brakes.


                        COUNSEL

Cyle A. Cramer (argued), William G. Jungbauer, and John
D. Magnuson, Yaeger & Jungbauer Barristers PLC, Saint
Paul, Minnesota; for Plaintiff-Appellant.
David M. Morrell (argued) and Jacqueline M. Holmes, Jones
Day, Washington, D.C.; Shelby B. Smith, Jones Day,
Pittsburgh, Pennsylvania; Tim D. Wackerbarth, Callie A.
Castillo, and Andrew G. Yates, Lane Powell PC, Seattle,
Washington; for Defendant-Appellee.
4             PARKER V. BNSF RAILWAY COMPANY

OPINION

GOULD, Circuit Judge:

    Curtis Rookaird, through his estate representative Paul
Parker, challenges his termination from BNSF Railway
Company (BNSF) under the anti-retaliation provision of the
Federal Railroad Safety Act (FRSA), 

(d).
After a jury found in Rookaird’s favor, the Ninth Circuit
vacated the verdict and remanded the case to the district
court to reconsider its partial summary judgment for
Rookaird on the issue of whether his performing an air-brake
test had contributed to BNSF’s decision to discharge him.
Rookaird v. BNSF Ry. Co., 

 (9th Cir. 2018)
(Rookaird I). On remand, the district court conducted a
bench trial on the issue and decided in BNSF’s favor. The
district court found that BNSF had conceded that Rookaird’s
refusal to stop performing the air-brake test contributed to its
decision to discharge Rookaird, but the court nonetheless
concluded that BNSF was entitled to an affirmative defense
by showing that the air-brake test “contributed very little” to
BNSF’s decision. Rookaird appeals, contending that the
district court erred in its analysis of BNSF’s affirmative
defense and in certain evidentiary rulings.
    We conclude that the district court’s application of the
FRSA does not comply with the text of the statute, which
prohibits the discriminatory discharge of an employee due
even “in part” to the employee’s refusal to violate or assist
in violating a railroad safety law, rule, or regulation. 

(a)(2). Nor is the district court’s conclusion
consistent with relevant case law, including our reasoning in
a prior case that, under the burden-shifting framework
required for FRSA cases, “[a plaintiff] would be entitled to
              PARKER V. BNSF RAILWAY COMPANY                  5


relief even if [the protected activity] played only a very small
role in [the employer’s] decision-making process.” Frost v.
BNSF Ry. Co., 

 (9th Cir. 2019) (citing
Rookaird I, 

). BNSF needed to demonstrate
by clear and convincing evidence not merely that it could
have fired Rookaird absent his engaging in the protected
activity, but rather that BNSF would have fired Rookaird. 

(b)(2)(B)(ii); 

(e)(4); see
Brousil v. U.S. Dep’t of Labor, Admin. Review Board, 

 (7th Cir. 2022) (citing Speegle v. Stone &
Webster Constr., Inc., ARB No. 13-074, 

,
at *7 (Dep’t of Labor Admin. Review Bd. Apr. 25, 2014)).
An FRSA affirmative defense is a “steep burden,” see
Araujo v. New Jersey Transit Rail Operations, Inc., 

 (3d Cir. 2013), particularly when a district court
finds that an employer concedes that the protected activity
contributed to the decision to terminate the employee who
engaged in it.
    We have jurisdiction under 

. We affirm
the district court’s evidentiary rulings, and we vacate and
remand the affirmative defense issue for further proceedings
consistent with this opinion.
        I. FACTS AND PROCEDURAL HISTORY
   A. Rookaird’s Tenure at BNSF
   1.    On and Before February 23, 2010
    Curtis Rookaird began working for BNSF, a national
freight train operator, in 2004. Before February 23, 2010,
Rookaird did not have a disciplinary record. He began his
shift at 2:30 p.m. on February 23, 2010, working on a three-
person “switcher” crew at BNSF’s Swift depot with engineer
Peter Belanger and brakeman Matthew Webb. Rookaird, as
6             PARKER V. BNSF RAILWAY COMPANY


a conductor, was in charge of the crew. The crew was
supposed to take a van from Swift to Ferndale, and then take
train cars back to Custer, where his crew would move 42
railway cars onto storage tracks. The crew was then
expected to take a van to Cherry Point to service BNSF
customers. The crew initially encountered an approximately
two-hour delay while waiting for the paperwork they needed
to start the day. At Custer, before moving the cars to storage,
Rookaird and his crew performed an air-brake safety test.
This test took around twenty to forty minutes to complete.
    Rookaird and his crew performed this air-brake test in
accordance with the company’s standard operating
procedures and recent changes to local processes. BNSF
train crews nationwide perform routine air-brake tests—
sometimes called “air tests”—on a daily basis. Air-brake
tests typically take twenty to twenty-five minutes to
complete. BNSF had started conducting remote audits to
ensure that employees were performing air-brake tests. On
February 11, weeks before Rookaird was at Custer with his
crew, BNSF implemented a new plan to manage the railway
in the Cherry Point area more efficiently by moving the
starting point for its switcher crews from Bellingham to
Swift. The new plan decreased employees’ hours, but did
not propose reducing or eliminating air-brake tests to gain
efficiency.
    BNSF, however, encountered less efficient operations
that month while implementing the new plan, with train cars
often sitting idle for longer than usual. BNSF Assistant
Superintendent Stuart Gordon testified during the bench trial
that complications were happening at that time, resulting in
delays. Trainmaster Dan Fortt, who reported to Gordon,
testified that BNSF was then “days behind” on their service
commitments, calling the place an “operational nightmare.”
              PARKER V. BNSF RAILWAY COMPANY                  7


Nonetheless, the BNSF company rules stated that, if an
employee was in doubt about whether to perform an air-
brake test, he should “take the safe course.”
    Fortt, headquartered in Canada and then serving BNSF
as a front-line supervisor, radioed Rookaird’s crew on
February 23 while they were conducting the air-brake test.
He asked them why they were doing it. Fortt commented:
“I’m not from around here, and I don’t know how you guys
do anything. But where I’m from, we don’t have to air test
the cars.” Fortt had the authority to instruct the crew more
explicitly to stop the air-brake test, but he did not do so. The
crew completed the test.
    Gordon, who supervised Fortt, had told Fortt to question
Rookaird about why the crew was performing an air-brake
test. Gordon objected that Rookaird’s crew’s performance
of the test was unnecessary. Gordon concluded that the crew
was inefficient that day because performing the air-brake test
had delayed the operation. When later asked during his
testimony which part of the job the crew was not doing
efficiently, Gordon urged: “An air test, I’m telling you.”
When asked for any other basis for the crew’s inefficiency,
Gordon did not mention any other specifics.
    Rookaird’s crew started moving the cars into storage.
The crew got another call from Fortt, this time asking how
much longer they would take to finish storing the cars. It
was around 7:30 p.m., and Rookaird estimated they would
take another hour or two. At Gordon’s direction, Fortt told
Rookaird’s crew to pack up and report back to the Swift
depot because another crew was going to finish the job.
Gordon called Rookaird’s crew back in part to question them
as to why they performed the air-brake test. Fortt agreed that
Rookaird’s crew was taking too long to do their job. Fortt
8             PARKER V. BNSF RAILWAY COMPANY


also thought that the air-brake test was unnecessary and
“contributing” to slowing the process down. Fortt was not
aware of any other reasons for the crew’s delay.
    Back at the Swift depot, Gordon told Rookaird and the
crew to “tie up.” Gordon claimed that he did not then plan
to pursue disciplinary action against Rookaird or the crew.
Rookaird completed his tie-up timeslip at 8:02 p.m. but did
not sign it. Rookaird went to the breakroom, where he had
a heated exchange with another employee, Ron Krich.
Gordon believed he overheard Rookaird encouraging Krich
to “slow down,” suggesting an intentional effort to log more
hours and earn overtime pay, though ultimately no one
testified to having heard Rookaird use those exact words.
Gordon came over and told Rookaird to leave. When
Rookaird did not leave, Gordon again told Rookaird to go
home. Rookaird then left. Rookaird reported that his final
off-duty time for that day was 8:30 p.m., within the thirty-
minute grace period permitted by BNSF’s policies and
practices.
    Gordon immediately conferred with Fortt and then
referred Rookaird’s crew for discipline in an e-mail to
Gordon’s immediate supervisor, Jeff Beck, as well as to the
General Manager of the Northwest Division, Doug Jones,
and investigating officer Robert Johnson. Gordon testified
that he told these individuals that Rookaird’s crew did an air-
brake test that day “that wasn’t necessary.”
    2.   The Investigation & Rookaird’s Termination
    On February 26, 2010, BNSF sent Rookaird a letter
alerting him that BNSF was investigating his actions on
February 23, 2010. The letter informed Rookaird that BNSF
was investigating him for: (1) failure to work efficiently,
(2) dishonesty in reporting his off-duty time, (3) failure to
              PARKER V. BNSF RAILWAY COMPANY               9


provide a signed tie-up timeslip, and (4) failure to comply
with instructions when specifically told to leave the
property. BNSF justified its discipline based on its Policy
for Employee Performance and Accountability (PEPA). The
PEPA established the consequences BNSF could impose for
each type of rule violation. The list included aggravated
offenses for which BNSF had the option to terminate an
employee based on a single violation. These aggravated
offenses included gross dishonesty and insubordination.
    Johnson conducted a twelve-hour investigation hearing
on March 12, 2010. Rookaird had union representation
present at the hearing. Johnson did not call Krich as a
witness to testify about whether Rookaird talked to him in
the breakroom about a “slow down.”
    Johnson sent the transcript to the director of employee
performance James Hurlburt, as well as to Doug Jones, who
had the decision-making authority to discharge Rookaird. In
an e-mail dated March 17, 2010, Johnson, as the
investigating officer, wrote to Hurlburt and Jones: “I am not
going to tell you this crew was the only crew that played the
slowdown game. However, I will tell you that this crew
made a fatal mistake and we have to make an example out of
them.” Jones later testified that Johnson’s email had
“passion associated with it” and “a lot of emotion put in
there.”
    Hurlburt recommended that Jones dismiss Rookaird.
Jones agreed, concluding that Rookaird had committed rule
violations that merited immediate dismissal. Jones testified
at the bench trial that Rookaird could not have been
dismissed for failure to work inefficiently, because he did
not have any prior record of discipline for that. Jones did
10            PARKER V. BNSF RAILWAY COMPANY


testify, however, that Rookaird’s encouraging Krich to slow
down contributed to Jones’s decision.
     BNSF terminated Rookaird on March 19, 2010, effective
immediately. BNSF’s stated reasons for terminating
Rookaird echoed those given in the investigation notice
letter, all based solely on what happened on February 23:
(1) “failure to work efficiently,” (2) “dishonesty when
reporting [his] off duty time,” (3) “failure to provide a signed
[] [t]ie-up timeslip,” and (4) “failure to comply with
instructions when told to leave the property. . . .” BNSF also
disciplined the two other crew members who were with
Rookaird that day, Webb and Belanger, for their failure to
work efficiently. Webb and Belanger received a thirty-day
suspension and probation.
     B. Procedural History
    Rookaird sued BNSF in 2014 under the anti-retaliation
provision of the FRSA, 

(a)(2), (d),
alleging that BNSF discharged him in part for his refusal to
stop the air-brake test. BNSF claimed that it would have
fired Rookaird even if he had not engaged in the air-brake
test. The district court entered a partial summary judgment
in favor of Rookaird, concluding that the protected activity
was a contributing factor in his termination. The district
court found that disputed issues of material fact remained as
to whether Rookaird had engaged in an activity protected by
the FRSA and whether BNSF could prove its affirmative
defense. Rookaird I, 

. The case proceeded
to a jury trial in 2016 on these issues. The jury returned a
verdict for Rookaird and awarded him more than $1 million
in damages. 

   On BNSF’s first appeal, we affirmed in part that
Rookaird had engaged in a protected activity when he
                 PARKER V. BNSF RAILWAY COMPANY                        11


refused to stop the air-brake test. 

 at 455–59. 1 We
reversed in part, however, after concluding that, under the
relevant burden-shifting framework, the district court had
improperly conflated Rookaird’s prima facie and
substantive showings. 

. We concluded instead that
Rookaird was not entitled to summary judgment on the
contributing-factor element at the substantive stage of the
proceedings. 

 at 459–62. We vacated the jury verdict and
remanded. 

. We expressed no view on how the
district court should handle the issue of BNSF’s affirmative
defense on remand. 

     On remand, the district court determined that three
triable issues remained: (1) the contributing-factor element
of the substantive stage of Rookaird’s case, (2) BNSF’s
affirmative defense, and (3) damages. The court set a jury
trial for October 12, 2021.
    On September 11, 2021, Rookaird passed away. Paul
Parker, as the personal representative of Rookaird’s estate,
substituted for Rookaird as the plaintiff. The parties then
stipulated to a bench trial.
    The district court held a four-day bench trial in October
2021. The district court confronted two critical evidentiary
issues relating to the designation of certain witnesses’ prior
testimony and comparator evidence. We discuss these
evidentiary issues in turn, and then turn to the district court’s
decision.



1
  In our analysis, we noted that sufficient evidence supported the jury’s
finding that Rookaird refused “in good faith” to violate a railroad safety
rule or regulation by completing the air-brake test. Rookaird I, 

.
12            PARKER V. BNSF RAILWAY COMPANY


     1. Testimony Designations
    Plaintiff’s counsel sought to designate the previous trial
or deposition testimony of seventeen witnesses, including
Rookaird’s testimony. At a pretrial conference, the district
court said that it would “permit the testimony to come in as
[plaintiff’s counsel] presents, if he believes that that’s the
way he wants to present that portion of his case.” At the start
of the bench trial, the district court indicated that the
designated testimony “will be reviewed and considered,” but
not read into the record. The district court ordered plaintiff’s
counsel to file a declaration about the specific efforts that he
had taken to make witnesses available for live testimony
during the bench trial. Plaintiff’s counsel described
challenging circumstances with respect to witnesses who
had died, retired, lived out of state, or had developed mental
health problems that inhibited them from testifying.
Ultimately, the district court accepted the designated
testimony from many prior witnesses including Rookaird,
Hurlburt, Johnson, Webb, Belanger, and Beck. The district
court denied the designations for other remaining witnesses,
including Krich and Rookaird’s wife.
     2.   Comparator Evidence
    BNSF had sent Rookaird’s counsel a spreadsheet from
BNSF’s internal database with limited descriptions of other
employees’ disciplinary records. The district court granted
Rookaird’s request for more detailed information and
directed BNSF to produce relevant specific information
about twelve comparators that were selected by Rookaird.
BNSF provided Rookaird with information about three
employees who had no prior disciplinary record and who
were dismissed for “willful dishonesty,” including
falsification of their tie-up time records, among other
              PARKER V. BNSF RAILWAY COMPANY                13


violations. BNSF’s records revealed that other employees
received only a reminder, warning, suspension, or other
minor discipline for similar infractions.
   3. The District Court’s Decision
    The district court issued its Findings of Fact and
Conclusions of Law on March 28, 2022. In addition to the
facts stated above, the district court made a factual finding
of particular note: “BNSF concedes that Mr. Rookaird’s
conducting of the air test contributed to the crew’s supposed
inefficiency and delay.” The district court based this finding
on multiple grounds: Jones’s admission that he had fired
Rookaird in part because of the delays that occurred that day,
which included a twenty-five-minute delay for the air test;
Gordon’s admission that Rookaird’s crew was being
inefficient in part due to the air-brake test; and Fortt’s
admission that the air-brake test contributed to slowing down
the crew’s process.
    In its legal conclusions, the district court relied on this
factual finding to conclude: “BNSF concedes that the crew’s
inefficiency was partly caused by Mr. Rookaird’s decision
to conduct an air test—a test that BNSF managers thought
was unnecessary to conduct in the first place.” The court
continued: “Because Mr. Rookaird was fired for his
inefficiency and because the inefficiency was partly caused
by the protected activity of refusing to stop the air test, the
Court concludes that the air test ‘tend[ed] to affect in [some]
way the outcome of [BNSF’s] decision’ to fire Mr.
Rookaird.” And because refusing to stop the air-brake test
“affected” BNSF’s decision to terminate Rookaird, it was a
“contributing factor” in his termination. The district court
further concluded that Rookaird proved his substantive
14            PARKER V. BNSF RAILWAY COMPANY


burden to show that refusal to stop conducting the air-brake
test was a contributing factor in his dismissal.
     The district court nonetheless concluded that BNSF met
its burden to prove its affirmative defense—that is, to show
by clear and convincing evidence that, absent Rookaird’s
refusal to stop the air-brake test, BNSF would have still fired
him for “many reasons unrelated to his inefficiency.” The
district court reasoned: “[T]hough the air test was a
contributing factor in Mr. Rookaird’s termination, the Court
concludes that the test contributed very little.”
    The district court stressed that the air-brake test only
took twenty to forty minutes of the crew’s five-and-a-half
hours of work, and no BNSF officer explicitly commanded
Rookaird to stop the test. The district court’s conclusion
rested on Rookaird’s inaccurate and unsigned February 23
tie-up timeslip, Rookaird’s repeated refusal to leave work
despite Gordon’s two orders telling him to stop work, and
Rookaird’s exchange with Krich. The district court further
pointed to the routine nature of the air-brake test, combined
with the lesser discipline given to Rookaird’s two crewmates
Webb and Belanger. From this, the district court concluded
that BNSF, having satisfied its affirmative defense, was not
liable for unlawful retaliation under the FRSA. Plaintiff’s
counsel moved to alter or amend the judgment, or in the
alternative for a new trial. The district court denied the
motion on August 5, 2022.
    Rookaird timely appealed. On appeal, he contends that
the district court erred in concluding that BNSF established
                 PARKER V. BNSF RAILWAY COMPANY                           15


its affirmative defense in light of FRSA law and the record. 2
Rookaird also argues that the district court’s evidentiary
rulings, which excluded certain testimony offered by
plaintiffs and admitted evidence offered by BNSF
concerning BNSF’s new comparator evidence, constitute
reversible error.
                 II. STANDARD OF REVIEW
    After a bench trial, we review a district court’s
conclusions of law de novo, and we review its findings of
fact for clear error. See Yu v. Idaho State Univ., 

, 1241–42 (9th Cir. 2021). We review de novo the legal
inferences that a district court made while applying the law
to the facts. See Suzy’s Zoo v. Comm’r, 

(9th Cir. 2001). We review evidentiary rulings for abuse of
discretion and only reverse an evidentiary ruling for
prejudicial error. Wagner v. Cnty. of Maricopa, 

 (9th Cir. 2013).
                         III. DISCUSSION
    A. The Text and History of the FRSA
     Construction began on the nation’s first commercially
chartered railway in 1828 when Charles Carroll, the last
surviving signer of the Declaration of Independence, laid the
first stone in Baltimore Harbor. 3 In 1970, more than 140
years later, Congress enacted the FRSA as its first


2
  Rookaird also appeals the district court’s denial of his Fed. R. Civ. P. 59
motion to alter or amend the judgment, or in the alternative for a new
trial. In view of our decision, stated hereafter, we need not reach
Rookaird’s challenge to the denial of his Rule 59 motion.
3
 Library of Congress, Today in History – February 28, LOC Digital
Collections, at https://perma.cc/Z6SR-6TFG.
16              PARKER V. BNSF RAILWAY COMPANY


comprehensive railroad safety law. 4 The FRSA aims “to
promote safety in every area of railroad operations and
reduce railroad-related accidents and incidents,” affecting
railroad workers, passengers, and the general public. See 

. Important safety measures include the air-
brake tests that railway employees must perform. See
Rookaird I, 

. A problem with a train’s air-
brake system can contribute to a crash or derailment,
resulting in hazardous material spills, fatalities, or other
issues that can gravely impact the lives of persons on the
train or living nearby. 5 A train that cannot stop safely
threatens disaster for railroad crews and the general public.
   To encourage accurate reports about railroad safety,
Congress amended the FRSA, first in 1980 and again in
2007, to add anti-retaliation measures ensuring that
employees could report their safety concerns without fear.
See Araujo, 708 F.3d at 156–57, n.3 (citing H.R. Rep. No.
110-259, at 348 (2007) (Conf.Rep.), as reprinted in 2007
U.S.C.C.A.N. 119, 181); Lee v. Norfolk S. Ry. Co., 

, 629–30 (4th Cir. 2015) (citing the Federal Railroad
Safety Authorization Act of 1980, 

,


4
 See Frank J. Mastro, Preemption is Not Dead: The Continued Vitality
of Preemption Under the Federal Railroad Safety Act Following the
2007 Amendment to 

, 37 Transp. L. J. 1, 2 (2010).
5
  See Daniel Gilbert and Tom McGinty, Brake-Related Failures Dog
Freight Railroads, Wall St. J., July 16, 2013, at https://perma.cc/27EL-
EM6L; see also CSX Train Derailment with Hazardous Materials
Release, Hyndman, Pennsylvania, August 2, 2017 vii, 12 (N.T.S.B. Nov.
23, 2020), at https://perma.cc/5U7Q-T2EP; Katherine Shaver, Bad
Brakes Caused Derailment, Wash. Post, Mar. 6, 2002, at
https://perma.cc/XMD3-3Z3L; Ian Austen, A Decade After a Deadly
Derailment, Some Wonder if Canada’s Railroads Are Safe, N.Y.Times,
Feb. 24, 2023, at A12.
              PARKER V. BNSF RAILWAY COMPANY               17

 (1980); H.R. Conf. Rep. No. 110-259, at 348
(2007), as reprinted in 2007 U.S.C.C.A.N. 119, 180–81); see
also Christopher W. Bowman, Whistleblower Protections of
the Federal Rail Safety Act: An Overview, 8 Wm. Mitchell
J. L. & Prac. 1, 1 (June 2015).
   Under the FRSA as amended:

       A railroad carrier . . . may not discharge, . . .
       reprimand, or in any other way discriminate
       against an employee if such discrimination is
       due, in whole or in part, to the employee’s
       lawful, good faith . . . refus[al] to violate or
       assist in the violation of any Federal law, rule,
       or regulation relating to railroad safety . . . .

(a)(2).
    To prevail on an FRSA claim, the plaintiff must prove
four elements: (1) the plaintiff engaged in an FRSA-
protected activity; (2) the employer knew that the plaintiff
engaged in that protected activity; (3) the plaintiff suffered
an unfavorable personnel action; and (4) the protected
activity “was a contributing factor in the unfavorable
personnel action.” Rookaird I, 

 (citation
omitted). The “contributing factor” element is the only
element at issue in this appeal. To prove these four elements,
a plaintiff must meet the burdens of proof set forth in 

(b)(2)(B), which provides the rules and
procedures governing whistleblower cases under the
Wendell H. Ford Aviation Investment and Reform Act for
the 21st Century (AIR-21). 

(d)(2)(A)(i)
(incorporating section 42121(b)(2)(B) by reference); see
also Araujo, 708 F.3d at 156–57. As clarified by our earlier
opinion, the AIR-21 standard sets forth a burden-shifting
18            PARKER V. BNSF RAILWAY COMPANY


framework that contains two distinct stages: the prima facie
showing and the substantive showing.             

(b)(2)(B); Rookaird I, 

. In each
stage, if a plaintiff makes the required showing, the burden
shifts to the respondent, such that each of the two stages
contains two steps.
    At the prima facie stage, the plaintiff must first establish
the existence of facts sufficient to raise an inference that the
protected activity was a “contributing factor” in the
unfavorable      personnel      action.           

(b)(2)(B)(i); 

(e)(1)–(3).
Second, the employer then has the burden to demonstrate, by
clear and convincing evidence, that it “would have taken the
same unfavorable personnel action in the absence of that
behavior.” 

(b)(2)(B)(ii); 

(e)(4).
    If the analysis proceeds to the substantive stage, the first
step of the substantive analysis requires the plaintiff to
demonstrate by a preponderance of the evidence that the
protected activity was a “contributing factor” in the
unfavorable       personnel     action.         

(b)(2)(B)(iii); 

(a). If the
plaintiff makes this showing, the second step of the
substantive analysis again shifts the burden to the employer,
allowing the employer to present an affirmative defense.
“[I]f the respondent-employer demonstrates by clear and
convincing evidence that the employer would have taken the
same unfavorable personnel action in the absence of that
behavior,” the plaintiff cannot prevail.           

(b)(2)(B)(iv); 

(b); see also
Rookaird I, 

, 459–60.
              PARKER V. BNSF RAILWAY COMPANY                19


    While McDonnell Douglas has provided courts with a
default burden-shifting scheme to analyze discrimination
claims, the FRSA burden-shifting framework is “much more
protective of plaintiff-employees than the McDonnell
Douglas framework,” because a claimant need only show
that his protected activity was “a contributing factor” in any
disciplinary action or termination, “not the sole or even
predominant cause.” Araujo, 

 (citing 

(b)(2)(B)(ii)); see also Greatwide Dedicated
Transp. II, LLC v. U.S. Dep’t of Labor, 

(4th Cir. 2023) (quoting Formella v. U.S. Dep’t of Labor,

 (7th Cir. 2010) (internal citation omitted))
(the AIR-21 standard is “more favorable to the complaining
employee”); see also McDonnell Douglas Corp. v. Green,

 (1973).
    As the Supreme Court recently stated, “the contributing-
factor burden-shifting framework is meant to be more lenient
than most” employment discrimination burden-shifting
frameworks in that it “is not as protective of employers as a
motivating-factor framework.” Murray v. UBS Securities,
LLC, 

 (2024). “That is by design.” 

.     “Congress has employed the contributing-factor
framework in contexts where the health, safety, or well-
being of the public may well depend on whistleblowers
feeling empowered to come forward.” 

 We “cannot
override that policy choice by giving employers more
protection than the statute itself provides.” 

    We turn to the district court’s analysis of the substantive
stage of Rookaird’s claim followed by BNSF’s affirmative
defense.
20            PARKER V. BNSF RAILWAY COMPANY


     B. An FRSA Affirmative Defense at the Substantive
        Stage
     1. Rookaird’s Protected Activity Was a Contributing
        Factor
    At the outset, it is undisputed that Rookaird proved his
substantive case by showing, by a preponderance of the
evidence, that his refusal to stop conducting the air-brake test
was a contributing factor to BNSF’s decision to discharge
him. See 

(b)(2)(B)(iii); 

(a).
    The incorporation of a contributing factor standard into
the FRSA “reflects a judgment that ‘personnel actions
against employees should quite simply not be based on
protected [whistleblowing] activities’—not even a little bit.”
Murray, 601 U.S. at 36–37 (quoting Marano v. Dep’t of
Justice, 

 (Fed.Cir. 1993) (internal citation
omitted)) (cleaned up). The FRSA prohibits discharge or
reprimand due even “in part” to an employee’s lawful, good
faith refusal to violate a railroad safety law, rule, or
regulation. 

(a)(2). It is well-established
under the FRSA that “[a] ‘contributing factor’ includes ‘any
factor, which alone or in connection with other factors, tends
to affect in any way the outcome of the decision.’” Rookaird
I, 

 (quoting Gunderson v. BNSF Ry. Co., 

 (8th Cir. 2017)) (internal citation omitted).
    The contributing factor standard was intended to
overrule existing case law, which required a whistleblower
to prove that his protected conduct was a “‘significant,’
‘motivating,’ ‘substantial,’ or ‘predominant’ factor in the
adverse personnel action . . . .” Murray, 

(citation omitted). An FRSA contributing factor “may be
quite modest.” Frost, 

 (citing Rookaird I,
              PARKER V. BNSF RAILWAY COMPANY                21

). “The Supreme Court has interpreted
similar language as creating liability if the employee’s action
causes ‘even the slightest’ influence on the employer’s
decision.” Yowell v. Admin. Review Board, U.S. Dep’t of
Labor, 

 (5th Cir. 2021) (quoting CSX
Transp., Inc. v. McBride, 

, 692, 695–99
(2011)).
     The record plainly supports the district court’s
conclusion that Rookaird’s refusal to stop the air-brake test
contributed to his termination. The district court concluded,
at the substantive stage, that Rookaird’s decision to proceed
with the air-brake test “tend[ed] to affect in [some] way the
outcome of [BNSF’s] decision” to fire Rookaird, because
Rookaird was fired “in part” for his inefficiency on February
23. The district court based its conclusion on the testimony
of Jones, Gordon, and Fortt. Given the testimony evidence,
as noted above, the district court concluded: “BNSF
concedes that the crew’s inefficiency was partly caused by
Mr. Rookaird’s decision to conduct an air test.” “Because
Mr. Rookaird was fired for his inefficiency, . . . the air test
‘tend[ed] to affect in [some] way the outcome of [BNSF’s]
decision’ to fire Mr. Rookaird,” making the air-brake test a
“contributing factor” under the FRSA. Cf. Rookaird I, 

.
    Under the FRSA, the district court’s contributing factor
findings and conclusions affect BNSF’s ability to prove at
the affirmative defense stage that it would have terminated
Rookaird absent the air-brake test.
   2. BNSF’s Affirmative Defense
    Our review proceeds to the next and final step of the
burden-shifting framework, which is our primary question in
this appeal: whether BNSF proved, by clear and convincing
22            PARKER V. BNSF RAILWAY COMPANY


evidence, that it would have taken the same unfavorable
action against Rookaird absent his refusal to stop the air-
brake test. The district court concluded that, “though the air
test was a contributing factor in Mr. Rookaird’s termination,
. . . the test contributed very little.” Despite acknowledging
that Rookaird’s refusal to stop the test contributed in part to
the decision to terminate him, the district court nonetheless
determined “that BNSF is not liable for unlawful retaliation
under the [FRSA].” That conclusion can stand only if BNSF
was entitled to its affirmative defense.
    In the FRSA context, “[u]nder the AIR-21 standard, [a
plaintiff] would be entitled to relief even if [the protected
activity] played only a very small role in [the employer’s]
decision-making process.” Frost, 

. The
final stage of the AIR-21 burden-shifting framework allows
an employer to defeat a claim for unlawful retaliation under
the FRSA if the employer proves, by clear and convincing
evidence, that it would have taken the same unfavorable
personnel action absent the protected activity. See 

(b)(2)(B)(iv); 

(b); Rookaird I,

, 459–60. The clear and convincing standard
is an “intermediate burden of proof” between a
“preponderance of the evidence” and “proof beyond a
reasonable doubt.” Araujo, 

 (citation
omitted); see also OTR Wheel Eng’g, Inc. v. West Worldwide
Servs., Inc., 

, 1020 (9th Cir. 2019) (internal
citations omitted). The Supreme Court has described the
“clear and convincing” standard as “highly probable,” such
that the material offered “instantly tilt[s] the evidentiary
scales” in the direction of the party providing the proof.
Colorado v. New Mexico, 

 (1984) (cleaned
up). In other words, an employer must meet a “steep burden”
to prove an FRSA affirmative defense under the AIR-21
              PARKER V. BNSF RAILWAY COMPANY              23


framework. See Araujo, 

. The burden is
steep for FRSA defendants because, unlike defendants under
other whistleblowing statutes that utilize the AIR-21
framework, an FRSA employer cannot discharge an
employee for his protected activity even “in part.” See 

(a).
    We rely on the plain text of the FRSA and give the
statute’s words their “ordinary meaning.” See Araujo, 

 (cleaned up). “In part” ordinarily means relating
to a portion or division of a whole, to some extent. See Part
& In Part, Oxford English Dictionary (2d ed. 1989). Put
another way, “in part” means any amount greater than zero.
We will not adopt a reading of the FRSA that renders any of
its words as surplusage. See Rookaird, 

(cleaned up). The text of 

(a) does not
permit an employer to discharge an employee if that decision
is based, to any extent, on the employee’s engaging in the
protected activity. See Araujo, 

 (cleaned up).
    Because the FRSA is the controlling statute, we hold
that, in an FRSA action, the affirmative defense step in the
substantive stage of the AIR-21 framework cannot disregard
the FRSA’s original inquiry about whether unfavorable
action was due “in part” to the employee’s engaging in a
protected activity. 

(a)(2). Because we
rely on the language of the FRSA, we limit our holding to
FRSA actions. While the existence of an affirmative defense
means that an employer can defeat FRSA liability in some
circumstances, an employer faces a “steep burden,” see
Araujo, 

, particularly when the protected
activity plays a part—however small—within the contours
of the employer’s adverse personnel decision. An FRSA
employer may still be able to prove an affirmative defense
where a plaintiff shows only a correlation between the
24            PARKER V. BNSF RAILWAY COMPANY


protected activity and adverse action, but this is less likely
where a factfinder determines that the protected activity
caused an employer’s adverse action, even in part. This is
true because an employer’s grounds for an unfavorable
personnel action must be “independently significan[t]”—
necessary and sufficient—apart from the employee’s
engagement in the protected activity. See Brousil, 

 (citing Speegle, ARB No. 13-074, 

,
at *7). The employer cannot prevail unless it proves by clear
and convincing evidence that the discriminatory action still
would have occurred absent the protected activity. See id.;

(b)(2)(B)(iv); 

(b).
    While applying the FRSA affirmative defense standard,
the district court reasoned that BNSF could still prove its
affirmative defense because Rookaird’s refusal to stop the
air-brake test “contributed very little” to BNSF’s decision to
terminate him. The proper inquiry, however, is not whether
the protected activity “contributed very little” to the firing;
the proper inquiry is whether BNSF would have fired
Rookaird regardless of whether he had conducted an air-
brake test. See 

(b)(2)(B)(iv); 

(b). Under the FRSA, the protected activity
cannot contribute even “in part” to the employer’s
termination decision, so the FRSA affirmative defense
standard needs to proceed with an analysis about whether
and how the termination decision would have occurred
absent the protected activity, given that the protected activity
cannot contribute to the employer’s adverse action decision
even in part. See 

(a)(2); cf. Frost, 

; Murray, 

, 35–37, 39 (citations
omitted).
   Because we have not had much occasion to interpret
what clear and convincing evidence an employer would need
              PARKER V. BNSF RAILWAY COMPANY                25


to provide to meet its affirmative defense burden under the
FRSA, we look to our precedent and that of our sister circuits
to discern what this district court and others should consider.
As recognized by the Seventh Circuit in Brousil, the
Administrative Review Board has provided “guiding
factors” that factfinders can consider when deciding whether
an employer would have taken the same adverse action
against an employee absent any protected activity. Those
factors include “how ‘clear’ and ‘convincing’ the
independent significance is of the non-protected activity”
and “the facts that would change in the ‘absence of’ the
protected activity.” Cf. Brousil, 

 (citing
Speegle, ARB No. 13-074, 

, at *7). Put
another way, the FRSA requires the employer to prove what
it “would have done,” not merely what it could have done.
Cf. 

 As such, the FRSA tasks an employer with proving a
counterfactual scenario, such that the factual findings
“instantly tilt the evidentiary scales” in their direction.
Colorado, 

.
    When an employer presents circumstantial evidence to
prove its FRSA affirmative defense, such evidence may
include a lack of temporal proximity between the non-
protected activity and the unfavorable action; a poor
employee work history and disciplinary record; the
consistent application of the employer’s policies; similarly
situated comparators; and the appropriate proportionality of
the unfavorable action to the basis for it. Cf. Brousil, 

 (citing Speegle, ARB No. 13-074, 

, at *7); Van Asdale v. Int’l Game Tech., 

 (9th Cir. 2009) (holding, without reaching the
burden-shifting stage, that the employee’s “positive record”
could lead a reasonable factfinder to decide that the
protected activity contributed to the termination).
26            PARKER V. BNSF RAILWAY COMPANY


    To this end, an employer’s claim that the plaintiff was
“technically in violation of written rules” does not meet the
affirmative defense burden without proof that the employer
consistently applied the same or similar policies to similarly
situated comparator employees. See Araujo, 708 F.3d at
162–63; see also Greatwide, 

 (rejecting
FRSA affirmative defense without proof that employer
consistently terminated employees for similar violations
under a range of possible disciplines); BNSF Ry. Co. v. U.S.
Dep’t of Labor, 

, 640–41 (10th Cir. 2016)
(rejecting FRSA affirmative defense when employer did not
prove that it fired employees for similar violations); Pan Am
Ry. v. U.S. Dep’t of Labor, 

 (1st Cir. 2017)
(rejecting FRSA affirmative defense when employer did not
prove that dishonesty in other instances was “of a similar
character”); Fresquez v. BNSF Ry. Co., 

, 1307–
08 (10th Cir. 2022) (rejecting FRSA affirmative defense
when employer did not show consistent application of stand-
alone dismissible policy); cf. Brousil, 

 (citing
Speegle, ARB No. 13-074, 

, at *7); Kuduk
v. BNSF Ry. Co., 

 (8th Cir. 2014) (agreeing
that BNSF proved its affirmative defense after presenting
“uncontroverted evidence that it consistently enforced this
policy”).
    What’s more, an employer’s “shifting explanations” for
its discipline call into question whether it would have
administered the same discipline absent the protected
activity. See Vieques Air Link, Inc. v. U.S. Dep’t of Labor,

 (1st Cir. 2006); see also Greatwide, 

; BNSF Ry. Co., 

; Weatherford
U.S., L.P. v. U.S. Dept’ of Labor, 

 (6th
Cir. 2023).
                PARKER V. BNSF RAILWAY COMPANY                       27


    An FRSA plaintiff can further show an “overwhelming”
case of FRSA retaliation by presenting evidence that the
employer tried to dissuade him from engaging in the
protected activity. See BNSF Ry. Co., 

(rejecting FRSA affirmative defense when supervisors tried
to dissuade plaintiff from engaging in protected activity); cf.
Araujo, 

.
    Rookaird’s lack of disciplinary record, a tenuous offer of
proof from BNSF that it applied its policies consistently to
relevant comparators, and BNSF’s efforts to dissuade
Rookaird from performing the air-brake test raise questions
about how BNSF could have proved that it would have
terminated Rookaird absent the air-brake test in light of the
district court’s finding that BNSF conceded that the air-
brake test contributed to its decision to discharge Rookaird. 6
Rookaird had no disciplinary history at BNSF before
February 23, 2010, and BNSF provided no evidence that it
had planned to terminate, investigate, or otherwise
reprimand Rookaird before the events on February 23.
BNSF showed that gross dishonesty and insubordination

6
  The non-protected activity and the adverse action occurred in close
temporal proximity, as did the protected activity. See Brousil, 

 (citing Speegle, ARB No. 13-074, 

, at *7)
(cleaned up); Van Asdale, 

 (quotation omitted); Vieques
Air Link, 437 F.3d at 108–09 (concluding that the employer failed to
prove by clear and convincing evidence that the employee’s protected
activity was unconnected to the adverse personnel action where the
action “followed almost immediately on the heels of reports [plaintiff]
made about [] safety violations”); cf. BNSF Ry. Co., 816 F.3d at 639–41
(rejecting FRSA affirmative defense where investigation and
termination commenced within a month of the protected activity).
Because Rookaird’s protected and non-protected activity both occurred
proximate to his termination, this factor may not counsel strongly one
way or the other toward BNSF’s affirmative defense.
28           PARKER V. BNSF RAILWAY COMPANY


gave adequate stand-alone bases for dismissal after a single
violation, but dismissal was discretionary and not a
mandatory consequence for either violation. To show the
consistent application of its policies, BNSF relied on one
case with three comparators who were dismissed for willful
dishonesty in their tie-up slips, but BNSF only notified
Rookaird that the company was investigating and
terminating him for “dishonesty,” not “willful” or “gross”
dishonesty.
    In any event, the district court did not base its
conclusions on these comparators; it only considered that
BNSF suspended and placed on probation the other two
members of Rookaird’s crew for their failure to work
efficiently on February 23. But Rookaird’s fellow crewmen
make for poor comparators when they may very well have
been impermissibly reprimanded for the same protected
activity as Rookaird. The district court did not base its
decision on BNSF showing comparators who were fired for
insubordination. Rookaird’s supervisors, Fortt and Gordon,
both tried to dissuade Rookaird from performing the air-
brake test. Gordon concluded that the air-brake test delayed
the crew and recalled the crew from their shift based on
asserted inefficiency, and he did not state any other reason
to believe that the crew worked inefficiently.
    When we consider the propriety of an FRSA affirmative
defense, we ask whether a district court considered such
factors with the understanding that the protected activity
cannot contribute to the employer’s adverse action decision
even in part. See 

(a)(2); 

(b)(2)(B)(iv); 

(b). See, e.g.,
Araujo, 708 F.3d at 162–63; Greatwide, 72 F.4th at 558–60;
BNSF Ry. Co., 816 F.3d at 640–41; Pan Am Ry., 

; Fresquez, 52 F.4th at 1307–08; Weatherford U.S., L.P.,
              PARKER V. BNSF RAILWAY COMPANY                29

; cf. Brousil, 

 (citing Speegle,
ARB No. 13-074, 

, at *7); Kuduk, 

.
    We vacate and remand the affirmative defense issue for
the district court to consider whether BNSF met its burden
to prove that the company would have terminated Rookaird
absent his refusal to stop performing the air-brake test, given
that the air-brake test cannot contribute even in part to a
termination decision.
   C. Evidentiary Rulings
    Finally, Rookaird appeals two categories of evidentiary
rulings: (1) the exclusion of certain testimony designations;
and (2) the admission of BNSF’s comparator evidence.
    Under our abuse of discretion standard, we will not
reverse an evidentiary ruling unless the decision is “beyond
the pale of reasonable justification under the circumstances.”
Boyd v. City and Cnty. of San Francisco, 

(9th Cir. 2009) (quoting Harman v. Apfel, 

 (9th Cir. 2000)). In addition, “[a] party seeking
reversal for evidentiary error must show that the error was
prejudicial, and that the verdict was ‘more probably than not’
affected as a result.” 

 (quoting McEuin v. Crown Equip.
Corp., 

 (9th Cir. 2003)) (cleaned up);
see also Wagner, 

.
    Regarding the testimony designations, plaintiff’s
counsel argues that he relied upon prior assurances from the
district court that such evidence would be permitted. The
district court, however, had said that it would only consider
admitting such evidence whenever plaintiff’s counsel
presented it, without previously ruling that any designation
would be admitted. Plaintiff’s counsel also delayed the
30             PARKER V. BNSF RAILWAY COMPANY


presentation of his deposition designations and his
explanation of witness unavailability that might have
justified admitting the deposition testimony. The district
court appropriately weighed the probative value of these
designations and did so on a timeline that was reasonable
given the timing of the proposed designations. Finally, the
district court did admit the designated testimony of several
of Rookaird’s key witnesses. The decision to exclude certain
designated testimony by the district court is not “beyond the
pale of reasonable justification under the circumstances.”
See Boyd, 

 (quotation omitted). Moreover,
plaintiff’s counsel does not identify how these rulings
unfairly prejudiced his case, as he must. See 

 (quotation
omitted). We review evidentiary rulings only for abuse of
discretion, and we conclude that the district court did not
abuse its discretion in these rulings. See Wagner, 

.
    Similarly, the district court’s admission of the
comparator evidence late in the bench trial was reasonable
based on when plaintiff’s counsel initially received this
evidence and raised potential issues with it. As such, the
district court did not abuse its discretion by admitting the
comparator evidence. See Boyd, 

 (quotation
omitted); Wagner, 

.
     We affirm the district court’s evidentiary rulings.
                     IV. CONCLUSION
    The FRSA prohibits an employer from taking an adverse
action against an employee even “in part” based on their
engagement with a protected activity. See 

(a); 

(b)(2)(B); Frost, 

; Araujo, 

; Murray, 

, 35–
37, 39. Because of this language, specific to the FRSA, the
              PARKER V. BNSF RAILWAY COMPANY               31


district court erred in its analysis of BNSF’s proffered
affirmative defense when it reasoned that Rookaird’s air-
brake test could contribute to BNSF’s decision to fire him so
long as it was “very little.”
    We AFFIRM the district court’s evidentiary rulings, and
we VACATE and REMAND the judgment for further
proceedings consistent with this opinion based on the record
that the district court developed at the bench trial.
   Each party shall bear its own costs.


GRABER, Circuit Judge, dissenting:

    This is an easy appeal that warrants a short memorandum
disposition affirming the district court. The only question
before us is whether the court’s factual findings are clearly
erroneous; they are not. The majority opinion has distorted
the case beyond recognition by misreading both the relevant
statute and the district court’s decision and by telling the
district court to redo exactly what it already did right.
Moreover, the majority opinion’s mangling of the law will
affect a wide range of retaliation cases. I respectfully but
emphatically dissent.
   A. The District Court’s Analysis Was Sound.
    The Wendell H. Ford Aviation Investment and Reform
Act for the 21st Century (“AIR-21”) describes a
straightforward, well-understood set of substantive
provisions for proving claims of retaliation. The plaintiff
bears an initial burden to prove that protected activity was
one reason that contributed, even in small part, to dismissal.

(b)(2)(B)(iii); Rookaird v. BNSF Ry. Co.,

 (9th Cir. 2018). If the plaintiff meets that
32               PARKER V. BNSF RAILWAY COMPANY


burden, the statute provides that the defendant has an
affirmative defense: proving by clear and convincing
evidence that “the employer would have taken the same
unfavorable personnel action in the absence of that
behavior.” 

 § 42121(b)(2)(B)(iv); Rookaird, 

. In other words, even when protected activity
contributed to a firing decision, the employer can “defeat the
claim by demonstrating ‘by clear and convincing evidence
that the employer would have taken the same unfavorable
personnel action in the absence of [the protected activity].’”
Frost v. BNSF Ry. Co., 

 (9th Cir. 2019)
(alteration in original) (emphasis added) (quoting 

(b)(2)(B)(iv)). The employer may not retaliate, even
a little; but Congress chose to exempt the employer from
liability if the firing would have happened anyway. 1
    The reason why the AIR-21 standards are so well
understood is that Congress chose to apply those same
standards in a wide range of statutes, including Sarbanes-

1
   The distinction between the substantive case and the affirmative
defense can be explained using a simple analogy. Suppose that I am
hosting a dinner party, and I plan to serve lasagna as the main dish. On
the morning of the party, I realize that I am out of lasagna noodles and,
although I have many after-dinner teas, I do not have one of my favorite
teas to serve. I am pressed for time, but I decide to go to the grocery
store. Both facts—lack of pasta and lack of a favorite tea—may have
contributed to the decision to go shopping. But if I am asked after the
fact, I would report that, even if I had stocked plenty of my favorite tea,
I would have gone to the store anyway. After all, the most critical need
for the dinner party was the main dish. The lack of tea contributed to my
decision to go to the store, but I would have gone to the store regardless
of my tea supply. Similarly, even when protected activity contributed to
a firing decision, the employer escapes liability if the firing would have
happened anyway.         Nothing required Congress to provide this
affirmative defense, of course, but we must apply the statute that
Congress enacted.
              PARKER V. BNSF RAILWAY COMPANY                 33


Oxley Act of 2002, 18 U.S.C. § 1514A(b)(2); Motor Vehicle
and Highway Safety Improvement Act of 2012, 

(b)(2)(B); Surface Transportation Assistance Act,

(b); FDA Food Safety Modernization Act,
21 U.S.C. § 399d(b)(2)(C); Consumer Product Safety
Improvement Act of 2008, 

(b)(2)(B);
Energy Policy Act of 1992, 

(b)(3);
American Recovery and Reinvestment Act of 2009, 

(c)(1)(B), 

, 299; Criminal
Antitrust Anti-Retaliation Act of 2019, 15 U.S.C. § 7a-
3(b)(2); William M. (Mac) Thornberry National Defense
Authorization Act for Fiscal Year 2021, Pub. L. No. 116-
283, § 6314, 

, 4601 (amending 

(g)(3)(A)); Taxpayer First Act, 

(d)(2)(B). Most pertinent here is the Federal Railway
Safety Act (“FRSA”).
    The FRSA provides that a railroad carrier may not fire or
discipline an employee because the employee refused to
violate a railroad safety rule. 

(a). The
FRSA expressly incorporates the AIR-21 substantive
provisions, commanding that any enforcement action “shall
be governed under the rules and procedures set forth in
section 42121(b), including . . . the legal burdens of proof set
forth in section 42121(b).” 

 § 20109(d)(2)(A).
    The district court conducted a trial in order to determine
two questions: the initial substantive burden and the
affirmative defense. The district court found that Curtis
Rookaird met the initial burden of proving that air-brake
testing—a protected activity—was one factor that
contributed, albeit “very little,” to his dismissal. Parker v.
BNSF Ry. Co., No. 2:14-cv-00176-RAJ, 

,
at *6–*7 (W.D. Wash. March 28, 2022). Because the
“contributing factor” bar is so low, Rookaird established the
34               PARKER V. BNSF RAILWAY COMPANY


elements of the claim. See Frost, 

 (holding
that “‘contributing factors’ may be quite modest” and may
“play[] only a very small role” in the employer’s decision);
Rookaird, 

 (“A ‘contributing factor’ includes
any factor, which alone or in connection with other factors,
tends to affect in any way the outcome of the decision.”
(citations and some internal quotation marks omitted)). On
appeal, neither party challenges the district court’s first
determination.
    The district court next found that BNSF Railway
Company proved its affirmative defense by presenting clear
and convincing evidence that it would have fired Rookaird
anyway, even if Rookaird had not engaged in the protected
activity of testing the brakes. Parker, 

, at
*6–*7. That second finding is the only substantive issue on
appeal. 2
    The record amply supports the district court’s finding.
On February 23, 2010, Rookaird and two other employees
performed work, including about half an hour of conducting
air-brake tests on railcars. 

 at *1–*2. In the judgment of
the supervisor, the crew took far too long, and the supervisor
told the crew to come back to the depot. 

. Once the
crew returned, after about five-and-a-half hours of work
during which little was accomplished, the supervisor told the
crew to clock out and go home. 

 The other two employees
did as they were told. 

. Rookaird, however,
dishonestly recorded his time of departure as 8:30 p.m.,
approximately half an hour after the actual time, and he did
not sign his timesheet. 

. Rookaird also declined to

2
 I agree with the majority opinion that the evidentiary challenges fail. I
also follow the majority opinion’s lead in referring to the plaintiff as
“Rookaird.”
                PARKER V. BNSF RAILWAY COMPANY                        35


follow the supervisor’s instruction to go home; instead, he
started an argument with another employee, refused a second
command to go home, and left only after receiving a third
command to go home. 

 at *2–*3.
    After considering all the evidence, the district court first
explained that the air-brake testing “contributed very little”
to BNSF’s decision to fire Rookaird. 

. The air-brake
testing accounted for only twenty to forty minutes of the
crew’s five-and-a-half hours of inefficient work, no one told
the crew to stop the air-brake testing, and air-brake tests
were routine. 

 Unlike other violations, discussed below,
inefficient work is not an independently dismissible
violation.
    In addition to the air-brake testing’s being only a small
part of Rookaird’s inefficiency that day, “Rookaird was fired
for many reasons unrelated to his inefficiency.” 

(emphasis added). Specifically, BNSF fired Rookaird for
lying on his timesheet and failing to sign his timesheet,
violations of work rules that independently warranted
dismissal, and BNSF fired Rookaird for twice disobeying
orders to leave the premises and for causing a heated
argument with a co-worker while he remained on site, also
an independently dismissible violation. 

 at *6–*7.
Indeed, both the general manager who decided to fire
Rookaird and the Human Resources employee who
reviewed the record and concurred in the firing decision
testified that the dishonesty and insubordination justified
Rookaird’s dismissal. 3 In sum, the testing comprised only

3
  The Human Resources manager testified at the first trial, and the
transcript of his testimony was admitted at the second trial. The general
manager testified, in person, at the second trial, and the district judge
36               PARKER V. BNSF RAILWAY COMPANY


about ten percent of the time that Rookaird and his
crewmates worked inefficiently (which is not an
independently dismissible offense anyway), and the testing
had nothing at all to do with Rookaird’s dishonesty and
insubordination (either of which is an independently
dismissible offense).
    The court additionally observed that BNSF imposed a
much lesser sanction on the other two members of
Rookaird’s crew. 

. Although those crew members,
too, had worked inefficiently, they had not committed gross
dishonesty or insubordination. The lesser punishment for
the other crew members supports the conclusion that—
consistent with BNSF’s written policies—BNSF viewed
Rookaird’s dishonesty and insubordination as the most
egregious misconduct.
    The record thus strongly supports—if not compels—the
district court’s finding that BNSF met its burden of proving
the affirmative defense. I would affirm.
     B. The Majority Opinion Significantly Errs.
    The majority opinion errs in many significant ways,
which I group as follows: (1) the opinion ignores the “clear
error” standard of review; (2) the opinion crafts a new,
confusing, nonsensical, and unsupported legal standard and
pointlessly remands for the district court to apply that bizarre



observed that testimony firsthand. The district judge, as trier of fact and
assessor of credibility, was entitled to believe him. See, e.g., United
States v. Ginn, 

 (9th Cir. 1996) (holding that “we must
respect the exclusive province of the trier of fact to determine the
credibility of witnesses” (brackets and internal quotation marks
omitted)).
              PARKER V. BNSF RAILWAY COMPANY                37


standard; and (3) the opinion commits a laundry list of
additional errors.
   1. The Opinion Ignores the “Clear Error” Standard of
      Review.
    The only substantive issue on appeal is the district
court’s finding that BNSF would have fired Rookaird
anyway, even if he had not tested the air brakes. In a range
of contexts, we and other circuits consistently have held that
whether an employer would have fired an employee anyway
is a factual determination that is reviewed for clear error.
See Clairmont v. Sound Mental Health, 

(9th Cir. 2011) (holding that whether an employer “would
have reached the same adverse employment decision even in
the absence of the employee’s protected conduct” is “purely
a question of fact” (brackets and internal quotation marks
omitted)); see, e.g., Baloga v. Pittston Area Sch. Dist., 

, 752 n.7 (3d Cir. 2019) (citing an earlier precedent
for the rule that “whether the employer would have taken
[an] action regardless” is a “question[] for the jury”);
Koszola v. FDIC, 

 (D.C. Cir. 2005)
(holding that the appellate court reviews “for clear error”
“the district court’s finding by clear and convincing evidence
that the [employer] would have fired [the employee]
regardless of any alleged protected activity”); Johnson v.
Univ. of Cincinnati, 

 (6th Cir. 2000)
(holding that whether the employer “would have terminated
[the employee] in the absence of his protected conduct . . . is
a question of fact for the jury to decide”); Bellaver v. Quanex
Corp., 

 (7th Cir. 2000) (holding that
whether the employer “would have fired [the employee] in
the absence of discrimination” is a determination “best left
in the hands of a jury”); Hall v. Marion Sch. Dist. No. 2, 

 (4th Cir. 1994) (holding that the determination
38             PARKER V. BNSF RAILWAY COMPANY


“whether [the employee] would have been fired ‘but for’ her
protected speech . . . is a factual one, and therefore, is not to
be reversed absent clear error” (internal citation omitted));
Daniels v. Quinn, 

 (4th Cir. 1986) (holding
that “whether the employee would have been discharged ‘but
for’ [protected] speech” is a “classic motivational question
[that] is one of fact”).
    The majority opinion states at the outset that we review
the district court’s findings of fact for clear error, Op. at 15,
but the opinion nowhere applies that standard to the district
court’s finding. “We review a district court’s findings of fact
following a bench trial for clear error, . . . and [we] will
reverse only if the district court’s findings are . . . illogical,
implausible, or without support in inferences from the
record.” Chaudhry v. Aragón, 

 (9th Cir.
2023) (citations and internal quotation marks omitted). The
majority opinion never mentions the “illogical, implausible,
or without support” standard and never explains how the
district court’s amply supported factual finding contravenes
that standard. Instead, the opinion simply ignores the
applicable standard of review.
     2. The Opinion Manufactures Legal Error by
        Announcing a Nonsensical New Legal Standard.
    Apparently recognizing that no clear error exists, the
majority opinion manufactures legal error, suggesting that
the district court misunderstood the applicable legal
standard. The majority opinion is plainly mistaken. The
district court fully comprehended and faithfully applied the
correct legal rule.
    The statutory scheme is not complicated. Both as a
matter of logic and of statutory text, the affirmative defense
arises only if the plaintiff first proves that protected activity
               PARKER V. BNSF RAILWAY COMPANY                  39


contributed, even a little, to the employer’s firing decision.
The statute refers in earlier sub-parts to behavior that is
protected and then queries, in the affirmative defense,
whether the employer would have fired the employee “in the
absence of that behavior.” 

(b)(2)(B)(ii),
(iv) (emphasis added). In other words, we reach the
affirmative defense only after a plaintiff has proved that the
employer impermissibly considered protected conduct. The
finding of a contributing factor is the necessary predicate for
the affirmative defense, not some smoking gun that
disproves or discredits the affirmative defense (especially
where, as here, the district court found that the protected
conduct contributed only very little to the firing decision).
    The employer then has the burden of proving by clear
and convincing evidence that it would have fired the
employee anyway, if the employee had not engaged in
protected activity. As the majority opinion correctly
recognizes, this is a hypothetical, “counterfactual” inquiry
that asks what the employer would have done had the
protected activity not occurred. Op. at 25. Here is how we
have described the rule in more formal terms: Even when
protected activity contributes to a firing decision, the
employer can “defeat the claim by demonstrating by clear
and convincing evidence that the employer would have taken
the same unfavorable personnel action in the absence of the
protected activity.” Frost, 

 (brackets
omitted) (citation and internal quotation marks omitted).
     That is precisely the question that the district court asked,
and answered, here. The court could not have been clearer.
It stated the correct legal standard three separate times. “An
employer . . . can defeat the plaintiff’s claim if the employer
demonstrates, by clear and convincing evidence, that the
employer would have taken the same unfavorable personnel
40            PARKER V. BNSF RAILWAY COMPANY


action in the absence of the protected activity.” Parker, 

, at *5 (internal quotation marks omitted). “[A]n
employer may defeat the retaliation claim if it can
demonstrate by clear and convincing evidence that it would
have taken the same unfavorable action absent the protected
activity.” 

 “An employer can defeat a claim for unlawful
retaliation if it can prove, by clear and convincing evidence,
that the employer would have taken the same unfavorable
personnel action in the absence of the protected activity.” 

 (internal quotation marks omitted).             It twice
summarized the pertinent question here in light of that legal
standard: “whether BNSF could prove, by clear and
convincing evidence, that it would have fired Mr. Rookaird
absent the air test.” 

. And it twice applied that
standard in reaching its conclusion: “The Court concludes,
by clear and convincing evidence, that absent the air test
BNSF would have still fired Mr. Rookaird.” 

. “In
all, the Court forms the ‘abiding conviction’ that even if Mr.
Rookaird did not engage in the protected activity of refusing
to stop the air test, BNSF would have still fired him for his
gross dishonesty and insubordination. Thus, the Court
concludes that BNSF has successfully proved its defense by
clear and convincing evidence.” 

 (internal citation
omitted).
    The majority opinion disregards the obvious fact that the
district court fully appreciated and applied the correct legal
rule. Instead, the majority opinion announces a new,
confusing, nonsensical, and unsupported legal standard. The
majority opinion then vacates the district court’s decision
and remands for reconsideration under the baffling new
standard. I strongly disagree.
    The majority opinion reasons as follows. Unlike some
statutes, the wording of the FRSA includes the provision that
                 PARKER V. BNSF RAILWAY COMPANY                        41


an employer may not retaliate “in whole or in part” against
an employee. 

(a). According to the
majority opinion, the “in part” wording affects not only the
employee’s substantive case, but also the employer’s
affirmative defense. According to the majority opinion, “the
FRSA affirmative defense standard needs to proceed with an
analysis about whether and how the termination decision
would have occurred absent the protected activity, given that
the protected activity cannot contribute to the employer’s
adverse action decision even in part.” Op. at 24 (emphasis
added). We must consider the affirmative defense “with the
understanding that the protected activity cannot contribute to
the employer’s adverse action decision even in part.” Op. at
28. This nebulous standard is wrong in so many ways, it is
hard to know where to begin. 4
   Fundamentally, the majority opinion conflates the
employee’s substantive burden with the employer’s

4
  The majority opinion cannot mean that, any time protected activity
contributed a little to the firing decision, the affirmative defense is
unavailable. That ruling would nullify the affirmative defense and
contravene our caselaw and the law of all other circuits. E.g., Frost, 

; Pan Am Rys., Inc. v. U.S. Dep’t of Labor, 

(1st Cir. 2017); Metro-North Commuter R.R. Co. v. U.S. Dep’t of Labor,

 (2d Cir. 2018); Wiest v. Tyco Elecs. Corp., 

 (3d Cir. 2016); Greatwide Dedicated Transp. II, LLC v. U.S.
Dep’t of Labor, 

, 553–54 (4th Cir. 2023); Yowell v. Admin.
Review Bd., U.S. Dep’t of Labor, 

 (5th Cir. 2021);
Weatherford U.S., L.P. v. U.S. Dep’t of Labor, Admin. Bd., 

 (6th Cir. 2023); Brousil v. U.S. Dep’t of Labor, Admin.
Review Bd., 

 (7th Cir. 2022); BNSF Ry. Co. v. U.S.
Dep’t of Labor Admin. Review Bd., 

 (8th Cir. 2017);
Fresquez v. BNSF Ry. Co., 

 (10th Cir. 2022). That
ruling also would make no sense in light of the majority opinion’s
decision to remand, because it is undisputed that the air-brake testing
contributed to the firing decision.
42            PARKER V. BNSF RAILWAY COMPANY


affirmative defense. As we and other courts consistently
have held, the affirmative defense asks simply what the
employer would have done in the absence of the protected
activity. That counterfactual inquiry assumes that the
protected activity did not occur and asks what decision the
employer would have made. In considering the affirmative
defense, the legal standard that the employee must meet to
prove the substantive case passes out of the picture and is
simply irrelevant. The majority opinion cites a long list of
cases that purportedly support its novel rule. But not a single
case supports its new rule. As discussed in more detail
below, no case gives the “in part” wording any special
import at all. And no case comes anywhere near suggesting
that the “in part” wording has any effect whatsoever on the
affirmative defense. Instead, as we and other circuits have
repeatedly held, the affirmative defense asks simply whether
the employer would have fired the employee in the absence
of the protected activity. See supra note 4 (listing cases).
    The reason why the “in part” wording has no meaningful
effect is that the AIR-21 standard already encompasses the
fact that an employee has only a minimal burden of proving
retaliation. As we put it succinctly in Frost, “[u]nder the
AIR-21 standard,” an employee can meet the contributing-
factor standard “even if [the protected activity] played only
a very small role in BNSF’s decision-making process.” 

 (emphasis added). The substantive standards
here are no different than in any other case applying the AIR-
21 standards. Not a single case has held that the “in part”
wording has any effect whatsoever on either the employee’s
substantive case or the affirmative defense.
   Finally, the majority opinion’s new standard is
nonsensical. The affirmative defense asks simply what the
employer would have done if the factfinder assumes that the
              PARKER V. BNSF RAILWAY COMPANY                 43


protected activity never had occurred.           Because the
factfinder must assume that the protected activity does not
exist at all, it makes no sense for the factfinder also to keep
in mind the “understanding” that the employer cannot fire
the employee for protected activity, even in part. Op. at 28.
In considering the hypothetical world in which the employee
did not engage in protected activity, the answer is either “the
employer would have fired the employee anyway” or “the
employer would not have fired the employee.” Whatever
answer the factfinder reaches, the employee’s burden at the
initial substantive step cannot possibly affect that answer.
    I do not envy the district court in this case in
reconsidering its decision. I see no reason why the district
court could not simply reinstate its original order, adding the
notation that it has done so while bearing in mind that an
employer cannot retaliate even in part. The law ordinarily
does not suffer such irrelevant formalities. Nor do I envy
juries in future cases, or our court in future appeals, in
applying this nonsensical legal standard, which is premised
on a snippet of statutory text that relates only to the
substantive case, not to the affirmative defense.
    The majority opinion’s reason for relying on that
particular snippet of statutory text is a transparent attempt to
limit the damage that its opinion does to our caselaw. The
opinion specifically limits its holding to FRSA cases. Op. at
23. But its rule clearly applies more broadly, to all cases
involving the AIR-21 standards, because those standards
already encompass the minimal level of retaliation that an
employee must show.
44               PARKER V. BNSF RAILWAY COMPANY


     3. The Majority Opinion Commits a Laundry List of
        Additional Errors.
    The majority opinion’s flailing analysis also commits a
laundry list of additional errors. I address a few of them
here.
    a. The majority opinion mentions, no fewer than six
times, BNSF’s purported concession as to the contributing-
factor determination. Op. at 4–5, 13 (twice), 21, 27. The
opinion describes that purported concession as
“particularly” important and a “finding of particular note,”
and the opinion implies that the concession makes it harder
for BNSF to prove the affirmative defense. Id. at 5, 13.
Those statements are wholly illogical and unprecedented.
The affirmative defense kicks in only if the plaintiff
establishes an improper contributing factor. The majority
opinion cites no legal support, and none exists, for the
proposition that it matters how the plaintiff establishes that
fact—whether by “concession,” by a ruling at summary
judgment, by stipulation, by a finding by the trier-of-fact, or
otherwise. 5


5
  The purported “concession” at issue here is not a formal concession by
a party. To the contrary, the court conducted a trial to rule on this
disputed issue of fact. Parker, 

, at *1. In its post-trial
decision, the district court cited testimony by BNSF employees that they
considered the air-brake testing, and the court wrote that BNSF
“concedes” the issue. 

. Read in context, the court meant only
that BNSF’s own employees testified that they considered the testing;
the court clearly did not intend to give its statement any greater weight
than that. Regardless, as explained in text, whether BNSF formally
conceded the issue or simply lost at trial on the issue is irrelevant to
assessing the affirmative defense. The key point is that the contributing-
factor finding is merely a necessary predicate for the affirmative defense,
not some critical fact that by itself discredits the defense.
              PARKER V. BNSF RAILWAY COMPANY                 45


    b. As another example, BNSF concluded that Rookaird
was dishonest in recording his sign-out time as 8:30 p.m.,
because he actually signed out at 8:02 p.m. The opinion
implies that Rookaird was not in fact dishonest because the
sign-out time was “within the thirty-minute grace period
permitted by BNSF’s policies and practices.” Op. at 8. The
district court found to the contrary, Parker, 

, at *6–*7, and the majority opinion never explains
why that finding was clearly erroneous. Moreover, the
majority opinion misunderstands the “grace period.”
Nothing in the record suggests that an employee could add
30 minutes to their workday for no reason at all. The policy
appears to have set a goal for employees to log out for the
day within 30 minutes of completing actual work on the
railcars, presumably because, as was true with the work that
Rookaird’s crew performed on the day in question, the actual
labor sometimes was not near the computer system. A
similar policy applied to arrival times: an employee was
expected to be doing actual work on the railcars, or
elsewhere, within 30 minutes of signing in. But nothing in
the record, nor in common sense, suggests that employees
could add up to 60 minutes of work time just because a
computer system allowed it.
    To the contrary, every BNSF employee who testified on
the subject testified that Rookaird had no justification for
adding 28 minutes to his sign-out time and that, accordingly,
he violated company policy. Rookaird himself testified that
he had no justification for adding the time, other than the fact
that the computer system allowed it. The other two members
of Rookaird’s crew, who received the same command to sign
out, accurately logged their sign-out times. Evidence in the
record shows that BNSF had disciplined other employees for
adding time to their workdays without justification. The
46            PARKER V. BNSF RAILWAY COMPANY


majority opinion’s statement that Rookaird’s adding of 28
minutes to his workday was “within the 30-minute grace
period permitted by BNSF’s policies and practices,” Op. at
8, is wholly unsupported by the record. There is no question
that Rookaird was dishonest in completing his timesheet.
    c. The majority opinion implies that the district court
misunderstood the legal standard by deciding only whether
BNSF “could have” fired Rookaird. Op. at 5, 25. The
majority opinion implies that the court did not determine
whether BNSF “would have” fired Rookaird. 

 I am
baffled by the suggestion. As described in detail above, the
district court stated the legal standard eight times and, in all
eight instances, the court used the correct “would have”
formulation. Parker, 

, at *1, *5 (thrice), *6
(twice), *7 (twice). Nothing suggests that the court
misunderstood the legal standard.
    d. The majority opinion’s discussion of an employer’s
efforts to dissuade an employee from engaging in protected
activity is wrong on both the facts and the law. The majority
opinion states—as fact—that BNSF attempted to dissuade
Rookaird from engaging in protected activity. Op. at 27–29.
But the district court made no such factual finding, and the
majority opinion relies on its own inferences from
ambiguous testimony to reach that conclusion. The majority
opinion plainly steps outside its role as reviewing court and
impermissibly acts as finder of fact.
    The majority opinion compounds the factual error by
committing legal error. The opinion quotes BNSF Railway
Co. v. United States Department of Labor, 

(10th Cir. 2016), for the proposition that an employee
“can . . . show an ‘overwhelming’ case of FRSA retaliation
by presenting evidence that the employer tried to dissuade
              PARKER V. BNSF RAILWAY COMPANY                47


him from engaging in the protected activity.” Op. at 27. But
BNSF Railway used the word “overwhelming” only in a
parenthetical; to a “cf.” citation; describing another case as
having “less than overwhelming” facts. BNSF Railway, 

 (emphasis added). Retaliation cases are
inherently fact-specific, and no one factor necessarily
controls. Contrary to the majority opinion’s implication,
there is no rule that any time an employer attempts to
dissuade an employee, the employee necessarily has an
“overwhelming” case. And this entire topic is irrelevant here
because the district court did not find that BNSF engaged in
dissuasion.
     e. The majority opinion next appears to fault the district
court for reasoning, in part, that the air-brake testing
contributed very little to BNSF’s firing decision. As
described above, the district court found that BNSF
established the affirmative defense for a combination of
reasons: (1) the protected activity contributed very little to
the firing decision; (2) wholly apart from the protected
activity, Rookaird engaged in egregious conduct constituting
several independently dismissible violations; and (3) BNSF
imposed lesser sanctions on employees who did not engage
in that same unprotected conduct. The majority opinion
focuses on the first reason only and states: “The proper
inquiry, however, is not whether the protected activity
‘contributed very little’ to the firing; the proper inquiry is
whether BNSF would have fired Rookaird regardless of
whether he had conducted an air-brake test.” Op. at 24. The
district court plainly asked the proper question whether
BNSF would have fired Rookaird anyway; it did not inquire
solely into whether the protected activity contributed very
little. To the extent that the majority opinion reads the
48            PARKER V. BNSF RAILWAY COMPANY


district court’s opinion as relying solely on that one factor,
the majority opinion is clearly wrong.
     Nor was there anything improper about the district
court’s considering whether the protected activity played a
large or a small role in the decision to fire the employee. As
a matter of common sense, the role that the protected activity
played in the firing decision bears directly on the credibility
of an employer’s explanation that it would have fired the
employee in the absence of the protected activity. For
example, if the protected activity was the centerpiece of a
firing decision, an employer will have a much harder time
convincing a finder of fact that it would have fired the
employee anyway. Or, as here, if the protected activity
played only a small role and the nonprotected conduct was
egregious, then the employer’s “we would have fired him
anyway” explanation has more credibility.
    Nothing in the law suggests that a factfinder must
disregard the logically salient factor of the role that the
protected activity played in the firing decision. The majority
opinion cites no support for that unprecedented, irrational
rule, and the rule runs counter to the same decisions that the
majority opinion cites favorably. See, e.g., Brousil, 

 (“[T]he [Administrative Review Board] has
admonished factfinders to ‘holistically consider any and all
relevant, admissible evidence’ . . . [and] no circuit court or
later ARB decision has limited the factfinder’s ability to look
at all relevant evidence.”).
     f. The majority opinion misunderstands the employee’s
initial substantive burden of proving that protected activity
must have contributed to the firing decision. The opinion
states, without citation or other support: “An FRSA
employer may still be able to prove an affirmative defense
                PARKER V. BNSF RAILWAY COMPANY              49


where a plaintiff shows only a correlation between the
protected activity and adverse action, but this is less likely
where a factfinder determines that the protected activity
caused an employer’s adverse action, even in part.” Op. at
23–24. An employee must show that protected activity
actually contributed to the firing decision; merely showing
that some activity correlated with the firing decision will not
suffice. Rookaird, 908 F.3d at 462–63. The majority
opinion’s mischaracterization of the initial substantive
burden fails to respect the law of the case and will cause yet
more confusion in this—until now—settled area of law.
   I dissent.