[Unpublished]

Ruth Pierce brought suit under 42 U.S.C. § 1983, asserting claims that Dr. James Pang and Registered Nurse Bonnie Moore improperly detained her in an inpatient psychiatric unit following the expiration of a ninety-six-hour detention order. She alleged that her continued detention violated her due process rights under the United States and Missouri Constitutions and violated provisions of the Missouri Revised Statutes governing involuntary-commitment procedures. She also asserted state-law claims-for false imprisonment, assault and battery by forced medication, and intentional infliction of emotional distress. After a four-day jury trial, the jury returned general verdicts in favor of Pang and Moore, and judgment was entered on November 20, 2014. Pierce filed a motion for a new trial on December 18, 2014.

On January 10, 2015, Pierce died. Pang filed a Notice of Fact of Death in the district court twelve days later, on January 22. The district court2 denied Pierce’s motion for a new trial on April 2, and a notice of appeal was filed on Pierce’s behalf on April 30. On November 16, Pierce’s counsel filed in this court a motion to substitute *615Pierce’s conservator Shirley Dodd as the party representative for Pierce. The motion was taken with this appeal.

The substitution of parties after death is controlled by Rule 25(a) of the Federal Rules of Civil Procedure. Kaubisch v. Weber, 408 F.3d 540, 542 (8th Cir. 2005). Rule 25(a) provides that, after death of a party, “the action does not abate,” but “[t]he death shall be suggested upon the record and the action shall proceed in favor of or against the surviving parties.” Fed. R. Civ. P. 25(a)(2). Under Rule 25(a)(1), “the motion for substitution ... [must be] made not later than 90 days after the death is suggested upon the record by service of a statement of the fact of the death.” Fed. R. Civ. P. 25(a)(1). If the motion for substitution is not timely made, then “the action by ... the decedent must be dismissed.” Id. Although the ninety-day rule “appears to be mandatory,” Kaubisch, 408 F.3d at 542, the district court has the discretion under Rule 6(b) to permit an untimely motion for substitution if the failure to file the motion resulted from excusable neglect, Fed. R. Civ. P. 6(b).

Here, Pang filed and served the Notice of Fact of Death on January 22. Pursuant to Rule 25(a)(1), Pierce’s counsel had ninety days from January 22 to file a motion to substitute; however, this period expired on April 22—several days after the district court’s order denying Pierce’s motion for a new trial but eight days before the notice of appeal was filed.3 By the time the briefs in support of this appeal had been filed, Pierce’s counsel still had not filed the requisite motion for substitution. Further, at oral argument, counsel offered no reasons for this extreme delay, conceding that the failure to file the motion was not the result of excusable neglect. See Fed. R. Civ. P. 6(b). This action thus should have been dismissed once the ninety-day period established in Rule 25(a)(1) elapsed. See Kaubisch, 408 F.3d at 543. Because the ninety-day period elapsed on April 22, and the notice of appeal was not filed until April 30, the district court retained jurisdiction over this suit at the time the period elapsed. Cf. Liddell v. Bd. of Educ., 73 F.3d 819, 822 (8th Cir. 1996) (noting that district court is not divested of jurisdiction of “those aspects of the case involved in the appeal” until notice of appeal is filed (quoting Griggs v. Provident Consumer Discount Co., 459 U.S. 56, 58, 103 S.Ct. 400, 74 L.Ed.2d 225 (1982))). We thus remand to the district court with instructions to dismiss the suit. See Fed. R. Civ. P. 25(a)(1).4