**36 *1187 The police quickly identified the defendant as the person suspected of murdering the victim with a sawed-off shotgun. In an attempt to pinpoint the location of the fleeing suspect, the police caused the defendant's cell phone to be "pinged." 1 They did so without a warrant. The legality of that ping in these circumstances is the central legal issue in this murder case.

The police had learned the defendant's cell phone number within approximately four hours of the shooting. After receiving this information, the police contacted the defendant's cellular service provider (service provider) to request the real-time location of his cell phone pursuant to a "mandatory information for exigent circumstances requests" form. The service provider eventually "pinged" the defendant's cell phone, an action that caused the defendant's cell phone to transmit its real-time global positioning system (GPS) coordinates to the service provider. Once received, the cell phone's GPS coordinates were relayed to police, who used the coordinates, in combination with information from another witness, to identify a single address in Brockton as the defendant's likely location. Upon arriving at the Brockton address, police entered the home with the consent of the homeowner and located the defendant in an upstairs bedroom. After the defendant was arrested, police obtained and executed a search warrant for the bedroom and seized a sawed-off shotgun and a bulletproof vest as evidence of the defendant's involvement in the victim's shooting death.

The defendant moved to suppress the evidence seized by police, arguing that it was the fruit of an unlawful search under the Fourth Amendment to the United States Constitution and art. 14 of the Massachusetts Declaration of Rights. The motion judge agreed, and the defendant's suppression motion was allowed. A single justice of this court allowed the Commonwealth's application to pursue an interlocutory appeal and reported the appeal to the Appeals Court. We subsequently allowed the defendant's petition for direct appellate review.

*1188 This appeal raises an issue of first impression in Massachusetts: whether police action causing an individual's cell phone to reveal **37 its real-time location constitutes a search in the constitutional sense under either the Fourth Amendment or art. 14. For the reasons set forth below, we conclude that, under art. 14, it does. We also conclude, however, that in the circumstances of this case, the warrantless search was supported by probable cause and was reasonable under the exigent circumstances exception to the search warrant requirement. We therefore reverse the motion judge's allowance of the defendant's motion to suppress. 2 ^, 3

Background . We summarize the facts as found by the motion judge, supplemented by uncontested facts in the record implicitly credited by him. See Commonwealth v. Jones-Pannell , 472 Mass. 429 , 436, 35 N.E.3d 357 (2015), citing Commonwealth v. Isaiah I ., 448 Mass. 334 , 337, 861 N.E.2d 404 (2007), S . C ., 450 Mass. 818 , 882 N.E.2d 328 (2008).

At approximately 5:19 P . M . on August 10, 2012, a Brockton police officer responded to a reported shooting. When he arrived at the scene, the officer saw a black car in the driveway. He found the victim inside the car, unconscious, with a gunshot wound to the chest. The victim was transported to a hospital, where he was pronounced dead approximately one hour later. Police immediately began investigating the shooting.

An eyewitness to the shooting was interviewed by police at approximately 8:15 P . M . The eyewitness explained that he and the victim had been sitting in the black car parked in the driveway when a second car pulled up behind them. Two men got out of the second car and entered the house, returning to the car a few minutes **38 later. One of the men, later identified as the defendant, "engaged in an unfriendly exchange" with the victim. Following this exchange, the defendant pulled out a shotgun wrapped in tape and told the eyewitness and the victim to empty their pockets. After some arguing, the defendant shot the victim in the chest. The defendant and the other man with whom he had arrived then entered their vehicle and left the scene. The eyewitness stated that he had a clear view of the shooter, who was only approximately ten feet away at the time of the shooting. The eyewitness later identified the defendant from a photographic array.

During the course of this initial investigation, two officers also located and interviewed a witness who revealed that the *1189 defendant had a former girlfriend. Police later learned that the defendant's former girlfriend lived at an address on a particular street in Brockton.

By 9:10 P . M ., two officers interviewed the man who had been in the car with the defendant. He admitted that he had been present at the shooting and knew the defendant. At some point before the conclusion of the interview, he provided police with the defendant's cell phone number. He also informed the officers that he had dropped the defendant off at an intersection not far from the scene of the shooting and that the defendant still had the shotgun.

By 11 P . M ., the police had conducted numerous witness interviews and performed multiple identifications of the defendant using photographic arrays. They learned that the shotgun was "cut down in the front." On the basis of the information they received, a police officer sent a "mandatory information for exigent circumstance requests" form to the defendant's service provider. The officer provided the defendant's cell phone number and requested several pieces of information, including the "precise location ... (GPS location)" of the defendant's cell phone. 4 As grounds for the request, the officer wrote, "outstanding murder suspect, shot and killed victim with shotgun. Suspect still has shotgun." The service provider did not respond to the written request.

At approximately 12 A . M ., police still had not heard from the service provider. The officer called a telephone number that the service provider maintained for law enforcement use and requested the real-time latitude and longitude coordinates of the defendant's cell phone. The service provider "pinged" the defendant's **39 cell phone, thereby causing the cell phone to reveal its real-time GPS coordinates at the time of the ping. Once its location was revealed, the service provider relayed the cell phone's GPS coordinates to the police. The officer entered the coordinates in a common computer mapping program, which identified the cell phone as being in the "general location" of a particular street in Brockton. 5 Having already learned that the defendant's former girlfriend lived at a particular address on that street, police decided to investigate the former girlfriend's address.

Less than one hour later, multiple police officers approached the defendant's former girlfriend's house, announced their presence, and knocked on the door. The homeowner, the former girlfriend's father, opened the door. He indicated that he *1190 knew the defendant but did not believe that the defendant was at the house. He said that his daughter should be upstairs in her room, and he gave police permission to go upstairs and speak with her.

When officers reached the second floor, they eventually encountered a locked door. They knocked several times and ordered anyone inside to come out. The officers heard a male voice inside the bedroom say, "Shit." The defendant eventually opened the door, wearing nothing but boxer shorts. He was ordered to the ground and arrested. Officers thereafter conducted a protective sweep of the bedroom and observed a sawed-off shotgun and a bulletproof vest in plain view. They secured the scene while one officer requested a warrant to search the house. After receiving the warrant, police searched the house and seized, among other items, the shotgun and vest.

The defendant eventually moved to suppress the evidence seized from the bedroom, as well as his subsequent statements to police, **40 on the grounds that they were the fruit of a warrantless search of the real-time location of his cell phone. After conducting a three-day evidentiary hearing, the motion judge concluded that the ping of the defendant's cell phone was a search under the Fourth Amendment and art. 14 and that the search was not justified by the exigent circumstances exception to the warrant requirement.

Discussion . When reviewing a ruling on a motion to suppress, "we accept the judge's subsidiary findings of fact absent clear error but conduct an independent review of his ultimate findings and conclusions of law" (citation omitted). Commonwealth v. Tremblay , 480 Mass. 645 , 652, 107 N.E.3d 1121 (2018). In assessing the propriety of the motion judge's decision, we must make the threshold determination whether the ping of the defendant's cell phone constituted a search in the constitutional sense under either the Fourth Amendment or art. 14. If it did, we must determine whether conducting the search without a warrant was nonetheless reasonable under the exigent circumstances exception to the search warrant requirement. 6

1. Search . The Fourth Amendment and art. 14 protect individuals from unreasonable searches and seizures. For these constitutional protections to apply, however, the Commonwealth's conduct must constitute a search in the constitutional sense. Commonwealth v. Magri , 462 Mass. 360 , 366, 968 N.E.2d 876 (2012). A search in the constitutional sense occurs "when the government's conduct intrudes on a person's reasonable expectation of privacy." Commonwealth v. Augustine , 467 Mass. 230 , 241, 4 N.E.3d 846 (2014), S . C ., 470 Mass. 837 , 26 N.E.3d 709 (2015). See Katz v. United States , 389 U.S. 347 , 361, 88 S.Ct. 507 , 19 L.Ed.2d 576 (1967) (Harlan, J., concurring). An individual has a reasonable expectation of privacy if (i) the individual has "manifested a subjective expectation of privacy in the object of the search," and (ii) if "society is willing to recognize that expectation as reasonable" (citation omitted). Augustine , supra at 242, 4 N.E.3d 846 .

The defendant therefore bears the burden of establishing that the Commonwealth intruded on a subjective and *1191 objective expectation of privacy in his cell phone's real-time location information. See Commonwealth v. Miller , 475 Mass. 212 , 219, 56 N.E.3d 168 (2016). There does not appear to be a dispute as to whether the defendant **41 manifested a subjective expectation of privacy in this information. 7 Our analysis is therefore limited to whether this expectation of privacy was objectively reasonable.

The ubiquitous use of cell phones, and the technology allowing for the tracking of their location, have significantly enhanced the government's surveillance capabilities. Augustine , 467 Mass. at 247-248 , 4 N.E.3d 846 . See Carpenter v. United States , --- U.S. ----, 138 S.Ct. 2206 , 2214, 201 L.Ed.2d 507 (2018). In response, courts across the country, including our own, increasingly have been tasked with addressing whether these enhanced surveillance capabilities implicate any objectively reasonable expectations of privacy. In so doing, both this court and the United States Supreme Court have been careful to guard against the "power of technology to shrink the realm of guaranteed privacy" by emphasizing that privacy rights "cannot be left at the mercy of advancing technology but rather must be preserved and protected as new technologies are adopted and applied by law enforcement" (quotation and citation omitted). Commonwealth v. Johnson , 481 Mass. 710 , 716, 119 N.E.3d 669 (2019). See Kyllo v. United States , 533 U.S. 27 , 34, 35, 121 S.Ct. 2038 , 150 L.Ed.2d 94 (2001) ; Commonwealth v. Connolly , 454 Mass. 808 , 836, 913 N.E.2d 356 (2009) (Gants, J., concurring) (noting need to "establish a constitutional jurisprudence that can adapt to changes in the technology of real-time monitoring").

Neither this court nor the Supreme Court, however, has addressed the issue we confront today: whether police action that causes an individual's cell phone to transmit its real-time location intrudes on any reasonable expectations of privacy. 8 See **42 Carpenter , 138 S.Ct. at 2220 ("Our decision today is a narrow one. We do not express a view on matters not before us [such as] real-time [location information]"); Augustine , 467 Mass. at 240 n.24, 4 N.E.3d 846 ("we do not need to consider [real-time location information] in the present case"). For the reasons set forth below, we conclude that under art. 14, it does. 9 *1192 In analyzing society's reasonable expectations of privacy, this court considers "various factors," including the "nature of the intrusion." 10 ^, 11 **43 Commonwealth v. One 1985 Ford Thunderbird Auto ., 416 Mass. 603 , 607, 624 N.E.2d 547 (1993). This analysis is also "informed by *1193 historical understandings of what was deemed an unreasonable search and seizure when [the Constitutions were] adopted" (quotations omitted). Carpenter , 138 S.Ct. at 2214 . See Jenkins v. Chief Justice of the Dist. Court Dep't , 416 Mass. 221 , 229, 619 N.E.2d 324 (1993) ("we construe [art. 14] in light of the circumstances under which it was framed, the causes leading to its adoption, the imperfections hoped to be remedied, and the ends designed to be accomplished" [quotation and citation omitted] ).

The intrusive nature of police action that causes an individual's cell phone to transmit its real-time location raises distinct privacy concerns. When the police ping a cell phone, as they did in this case, they compel it to emit a signal, and create a transmission identifying its real-time location information. Matter of an Application of the U.S.A. for an Order Authorizing Disclosure of Location Info. of a Specified Wireless Tel ., 849 F.Supp.2d 526 , 534 (D. Md. 2011) ( Matter of an Application ) (describing that ping of cell phone "send[s] a signal directing the built-in satellite receiver in a particular [cell phone] to calculate its location and transmit the location data back to the service provider"). This action and transmission is initiated and effectively controlled by the police, and is done without any express or implied authorization or other involvement by the individual cell phone user. See id . (noting that cell phone ping is "undetectable to the [cell phone] user"). Without police direction, such data would also not otherwise be collected and retained by the service provider. See id .

**44 (noting that service providers "typically do not maintain records of the GPS coordinates of [cell phones] operating on their network"). Accordingly, in pinging a cell phone, the police "actively induce[ ] [it] to divulge its identifying information" for their own investigatory purposes. 12 Jones v. United States , 168 A.3d 703 , 713 (D.C. 2017).

We confidently conclude that such police action implicates reasonable expectations of privacy. 13 Indeed, society reasonably expects that the police will not be able to secretly manipulate our personal cell phones for any purpose, let alone for the purpose of transmitting our personal location *1194 data. 14 Cf. Connolly , 454 Mass. at 835 , 913 N.E.2d 356 (Gants, J., concurring) (describing privacy concerns under art. 14 where police installed GPS tracking device on vehicle **45 without defendant's knowledge); State v. Andrews , 227 Md. App. 350 , 392, 134 A.3d 324 (2016) ("no one expects that their [cell] phone information is being sent directly to the police department" [citation omitted] ); State v. Earls , 214 N.J. 564 , 587, 70 A.3d 630 (2013) ("no one buys a cell phone to share detailed information ... with the police"). A person obtains a cell phone for a variety of reasons, including for "the purpose of making and receiving telephone calls," to communicate with others electronically, or perhaps to conduct business. See Augustine , 467 Mass. at 264 , 4 N.E.3d 846 (Gants, J., dissenting). See also Riley v. California , 573 U.S. 373 , 394-395, 134 S.Ct. 2473 , 189 L.Ed.2d 430 (2014) (describing cell phone use); Earls , supra at 587-588, 70 A.3d 630 . More particularly, individuals obtain cell phones because carrying one has become "indispensable to participation in modern society." Carpenter , 138 S.Ct. at 2220 . The decision to obtain a cell phone, however, does not in any way authorize police to independently, and without judicial oversight, invade or manipulate the device to compel it to reveal information about its user. Nor does it operate to reduce one's expectation of privacy against such action.

Manipulating our phones for the purpose of identifying and tracking our personal location presents an even greater intrusion. In today's digital age, the real-time location of an individual's cell phone is a proxy for the real-time location of the individual. Indeed, cell phones are "an indispensable part of" daily life and exist as "almost permanent attachments to [their users'] bodies" (citation omitted). Augustine , 467 Mass. at 245-246 , 4 N.E.3d 846 . Cell phones "physically accompany their users everywhere" such that tracking a cell phone results in "near perfect surveillance" of its user. Carpenter , 138 S.Ct. at 2218 . Augustine , supra at 246, 4 N.E.3d 846 . The Commonwealth's ability to identify a cell phone's real-time location is therefore, in essence, the ability to identify the real-time location of its user.

The fact that cell phones are now "almost a feature of human anatomy" effectively means that individuals are constantly, and often unknowingly, carrying a hidden tracking device that can be activated by law enforcement at any moment, subject only to the constraints of whether law enforcement knows the phone number and whether the cell phone is turned on (quotation and citation omitted). Carpenter , 138 S.Ct. at 2218 . See Matter of an Application , 849 F.Supp.2d at 540 ("Location data from a cell phone ... enables law enforcement to locate a person entirely divorced from all visual observation. Indeed, this is ostensibly the very characteristic that makes obtaining location data a desirable **46 method of locating the subject ..."). This extraordinarily powerful surveillance tool finds no analog in the traditional surveillance methods of *1195 law enforcement and therefore grants police unfettered access "to a category of information otherwise unknowable." Carpenter , supra . Indeed, prior to the advent of cell phones, law enforcement officials were generally required, by necessity, to patrol streets, stake out homes, interview individuals, or knock on doors to locate persons of interest. See United States v. Jones , 565 U.S. 400 , 429, 132 S.Ct. 945 , 181 L.Ed.2d 911 (2012) (Alito, J., concurring) (recognizing that, "[i]n the pre-computer age," law enforcement surveillance tools were limited and thus "the greatest protections of privacy were neither constitutional nor statutory, but practical"); ibr.US_Case_Law.Schema.Case_Body:v1">id . 415-416 , 132 S.Ct. 945 (Sotomayor, J., concurring) ("because GPS monitoring is cheap ... and ... proceeds surreptitiously, it evades the ordinary checks that constrain abusive law enforcement practices: limited police resources and community hostility" [quotation and citation omitted] ). For this reason, society's expectation has been that law enforcement could not secretly and instantly identify a person's real-time physical location at will. See id . at 429 , 132 S.Ct. 945 (Alito, J., concurring) (discussing societal expectations with respect to GPS tracking); Connolly , 454 Mass. at 835 , 913 N.E.2d 356 (Gants, J., concurring) (noting that "[i]n the context of GPS," individuals reasonably expect that they will not be "contemporaneously monitored except through physical surveillance"); Jones , 168 A.3d at 712-713 (noting that society does not reasonably expect police to be able to instantly locate individuals).

Allowing law enforcement to immediately locate an individual whose whereabouts were previously unknown by compelling that individual's cell phone to reveal its location contravenes that expectation. See Jones , 168 A.3d at 714-715 (noting law enforcement's "powerful person-locating capability that private actors do not have" invades reasonable expectations of privacy); Earls , 214 N.J. at 586 , 70 A.3d 630 ("Using a cell phone to determine the location of its owner ... involves a degree of intrusion that a reasonable person would not anticipate"). Although our society may have reasonably come to expect that the voluntary use of cell phones -- such as when making a phone call -- discloses cell phones' location information to service providers, see Augustine , 467 Mass. at 263 , 4 N.E.3d 846 (Gants, J., dissenting), and that records of such calls may be maintained, our society would certainly not expect that the police could, or would, transform a cell phone into a real-time tracking device without judicial oversight. Cf.

**47 Commonwealth v. Rousseau , 465 Mass. 372 , 382, 990 N.E.2d 543 (2013) ("a person may reasonably expect not to be subjected to extended GPS electronic surveillance by the government"); Andrews , 227 Md. App. at 394-395 , 134 A.3d 324 ("cell phone users have an objectively reasonable expectation that their cell phones will not be used as real-time tracking devices through the direct and active interference of law enforcement"); Earls , supra at 586, 70 A.3d 630 . The power of such unauthorized surveillance is far "too permeating" and too susceptible to being exercised arbitrarily by law enforcement -- precisely the type of governmental conduct against which the framers sought to guard. See Commonwealth v. Blood , 400 Mass. 61 , 71, 507 N.E.2d 1029 (1987) (noting that art. 14 was adopted to protect against "search policies ... which allowed officers of the crown to search, at their will , wherever they suspected [evidence of criminal activity] to be" [emphasis in original; citation omitted] ). See also Carpenter , 138 S.Ct. at 2214 ("The basic purpose of [the Fourth] Amendment ... is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials" [quotations and citation omitted] ). It *1196 would also require a cell phone user "to turn off the cell phone just to assure privacy from governmental intrusion." Tracey v. State , 152 So.3d 504 , 523 (Fla. 2014).

To allow such conduct without judicial oversight would undoubtedly "shrink the realm of guaranteed privacy" under art. 14 and leave legitimate privacy rights at the "mercy of advancing technology." See Kyllo , 533 U.S. at 34, 35 , 121 S.Ct. 2038 . Accordingly, we conclude that by causing the defendant's cell phone to reveal its real-time location, the Commonwealth intruded on the defendant's reasonable expectation of privacy in the real-time location of his cell phone. 15 The Commonwealth therefore conducted a **48 search in the constitutional sense under art. 14. 16

The Commonwealth nonetheless contends that under our decision in *1197 Commonwealth v. Estabrook , 472 Mass. 852 , 858 & n.12, 38 N.E.3d 231 (2015), where we held that police may obtain up to six hours of historical "telephone call" cell site location information (CSLI) without obtaining a warrant (six-hour rule), the single ping of the defendant's cell phone was "too brief to implicate [a] person's reasonable privacy interest" and thus does not constitute a search in the constitutional sense (citation omitted). This argument, however, ignores both the clear language of Estabrook and the fundamental differences between accessing historical "telephone call" CSLI and police action that causes a cell phone to identify its **49 real-time location.

As we stated in Estabrook , 472 Mass. at 858 n.12, 38 N.E.3d 231 , albeit without elaboration, the six-hour rule applies only to historical "telephone call" CSLI. Historical "telephone call" CSLI is collected and stored by the service provider in the ordinary course of business when the cell phone user voluntarily makes or receives a telephone call. In this context, the six-hour rule is consistent with reasonable societal expectations of privacy. In contrast, there is nothing voluntary or expected about police pinging a cell phone, and the six-hour rule therefore does not apply.

2. Reasonableness of search . Our conclusion that the Commonwealth committed a search in this case does not, however, decide the ultimate question of the search's constitutionality. Indeed, art. 14 prohibits only unreasonable searches. See ibr.US_Case_Law.Schema.Case_Body:v1">id . ("Every subject has a right to be secure from all unreasonable searches ..." [emphasis added] ).

Where police conduct a search without a warrant, the search is presumptively unreasonable. Commonwealth v. White , 475 Mass. 583 , 588, 59 N.E.3d 369 (2016). Because the "ultimate touchstone" of art. 14 is reasonableness, however, "the warrant requirement is subject to certain carefully delineated exceptions." Commonwealth v. Entwistle , 463 Mass. 205 , 213, 973 N.E.2d 115 (2012), cert. denied, 568 U.S. 1129 , 133 S.Ct. 945 , 184 L.Ed.2d 736 (2013). One such exception is where police can establish probable cause and exigent circumstances. Commonwealth v. Alexis , 481 Mass. 91 , 96, 97, 112 N.E.3d 796 (2018). "Under the exigent circumstances exception to the warrant requirement, 'there must be a showing that it was impracticable for the police to obtain a warrant, and the standards as to exigency are strict.' " Id . at 97 , 112 N.E.3d 796 , quoting Commonwealth v. Forde , 367 Mass. 798 , 800, 329 N.E.2d 717 (1975). The Commonwealth bears the burden to demonstrate both probable cause and exigent circumstances. Commonwealth v. Molina , 439 Mass. 206 , 209, 786 N.E.2d 1191 (2003).

The defendant does not contest that there was probable cause to believe that he had committed the crime. 17 Our analysis is therefore limited to whether police were confronted with an exigency such that it was impracticable for them to obtain a warrant.

We evaluate "whether an exigency existed, and whether the response of the police was reasonable and therefore lawful ... in relation to the scene as it could appear to the officers at the time, **50 not as it may seem to a scholar after the event with the benefit of leisured retrospective analysis." Commonwealth v. Young , 382 Mass. 448 , 456, 416 N.E.2d 944 (1981). Accordingly, we do not examine facts in isolation; rather, we take into account the totality of the circumstances. See *1198 Forde , 367 Mass. at 801 , 329 N.E.2d 717 . Although a number of factors have been considered in evaluating the existence of exigent circumstances and the reasonableness of police response, 18 we have tended to focus on three factors. Commonwealth v. Figueroa , 468 Mass. 204 , 213, 9 N.E.3d 812 (2014). See Commonwealth v. Tyree , 455 Mass. 676 , 687, 687 n.24, 919 N.E.2d 660 (2010). Specifically, we consider whether police had "reasonable grounds to believe that obtaining a warrant would be impracticable under the circumstances because the delay in doing so would pose a significant risk that [ (1) ] the suspect may flee, [ (2) ] evidence may be destroyed, or [ (3) ] the safety of the police or others may be endangered." Figueroa , supra . Although each of these risks need not be present for there to be exigent circumstances, each was present here. 19 See id .

As to the risk of flight in this case, there were reasonable grounds to believe that the defendant would have been aware that police would be looking for him. He had shot the victim in the daytime in the presence of others, and thus he likely knew that his crime was likely to attract the attention of authorities. He was also undoubtedly aware that there were at least two witnesses who could identify him: the second person in the defendant's vehicle and the second passenger in the victim's vehicle. Cf. Figueroa , 468 Mass. at 213-214 , 9 N.E.3d 812 (risk of flight present where murder suspect shot victim without wearing mask and subsequently could attempt to evade police). Contrast Alexis , 481 Mass. at 100-101 , 112 N.E.3d 796 (no exigent circumstances where "crime occurred the previous day, and there was no evidence that the defendant even knew or had **51 reason to know that he was a suspect before the police arrived at his home"); Tyree , 455 Mass. at 687 , 687 n.24, 919 N.E.2d 660 (2010) (no risk of flight where defendant committed robbery while masked, at night, and no witnesses would recognize him). The suspect was already on the run after fleeing the scene, and there was a risk that, with the passage of time, he would take further precautions to effectuate his escape if police did not locate him.

As to the risk of destruction of evidence, the record reflects that police learned that the defendant still possessed the sawed-off shotgun at the time he fled the scene of the shooting. Because a sawed-off shotgun is per se illegal, it requires ongoing concealment from authorities. See G. L. c. 269, § 10 ( c ). This fact, when coupled with the fact that the suspect likely knew he could be identified and would have reason to fear capture, gave police reasonable grounds to believe that there was a risk that the suspect would attempt to conceal or destroy the shotgun before he was located by police. Cf. Figueroa , 468 Mass. at 214 , 9 N.E.3d 812 (likelihood of being recognized by eyewitness created risk that suspect would eliminate forensic evidence). Contrast *1199 Commonwealth v. Huffman , 385 Mass. 122 , 126, 430 N.E.2d 1190 (1982) (no risk of destruction of evidence where marijuana packagers had no reason to believe police were investigating them).

Finally, police also had reasonable grounds to believe that the defendant posed an immediate risk to the safety of police and others. The suspect possessed a sawed-off shotgun, a dangerous and per se illegal weapon. See G. L. c. 269, § 10 ( c ). In contrast to a handgun or a knife, a sawed-off shotgun presents an ongoing danger; such a weapon has no lawful function, and its owner continues to demonstrate a willingness to violate the law by possessing it. In these circumstances, police had reasonable grounds to believe that the suspect not only had shot and killed once with the shotgun, but that he had brutally murdered a person without an apparent motive. This was not a case in which the threat posed by the suspect was limited to a particular victim, for a particular purpose, such that the circumstances that had led to the shooting dissipated thereafter. Contrast Tyree , 455 Mass. at 678 , 689 & n.28, 919 N.E.2d 660 (no ongoing danger where robbery was complete and suspect was not "on the run"). Rather, the officers had reasonable grounds to believe that if the suspect shot one person, when unprovoked and seemingly undeterred by fear of discovery or reprisal, other individuals were in danger as well. See Figueroa , 468 Mass. at 214 , 9 N.E.3d 812 (fear that "hot-headed gunman" who still possessed **52 weapon could take nearby children as hostages); Commonwealth v. Donoghue , 23 Mass. App. Ct. 103 , 108, 499 N.E.2d 832 (1986), cert. denied, 481 U.S. 1022 , 107 S.Ct. 1908 , 95 L.Ed.2d 513 (1987) ("unusually brutal" nature of assault suggested suspect was dangerous and that there might be other victims). Indeed, law enforcement officials' concern about the danger posed by the shotgun was reflected in the "Exigent Circumstance Requests" form sent by facsimile to the service provider, which stated that that there was an "[o]utstanding murder suspect, shot and killed victim with shotgun. Suspect still has shotgun."

With these considerations in mind, we conclude that under the circumstances at the time the defendant's cell phone was pinged, the police had reasonable grounds to believe that obtaining a warrant would be impracticable because taking the time to do so would have posed a significant risk that the suspect may flee, evidence may be destroyed, or the safety of the police or others may be endangered. Cf. Figueroa , 468 Mass. at 213-214 , 9 N.E.3d 812 . See Carpenter , 138 S.Ct. at 2223 (noting that certain "exigencies" may permit police to access cell phone location information without warrant, such as need to "pursue a fleeing suspect, protect individuals from imminent harm, or prevent the imminent destruction of evidence").

Faced with this exigency, the police acted entirely reasonably in pinging the defendant's cell phone to determine its location. 20 Accordingly, the motion judge erred *1200 in concluding that the warrantless ping of the defendant's cell phone was not justified by exigent circumstances and the allowance of the defendant's motion **53 to suppress must therefore be reversed.

So ordered .

LENK, J. (concurring, with whom Gants, C.J., joins).

I agree with the court that the "pinging" of a cellular telephone, even once, constitutes a search under art. 14 of the Massachusetts Declaration of Rights that ordinarily requires a warrant. I also agree with the court that, in the exigent circumstances here, a warrant was not required. Although I quarrel with certain aspects of the court's exigency analysis, I write separately chiefly because I take issue with the weight my colleagues implicitly place on property rights in concluding that a warrantless ping is unconstitutional.

A search does not require governmental manipulation of an individual's property. Concluding so would carve out a gaping exception for violations of an individual's privacy that do not rest on government interference with an individual's property. Federal law, and this court's more recent jurisprudence, have moved beyond a focus on the nature of the government's physical intrusion in determining whether a search has occurred. It is rather the right to be let alone, including and especially within the home, that mandates that the government obtain a search warrant, supported by probable cause, before it may locate a person through a ping of a cellular telephone.

1. The right to be let alone . "Article 14, like the Fourth Amendment, was intended by its drafters not merely to protect the citizen against the breaking of his [or her] doors, and the rummaging of his [or her] drawers," but to confer, "as against the government, the right to be let alone -- the most comprehensive of rights and the right most valued by civilized [people]" (quotation and citations omitted). Commonwealth v. Blood , 400 Mass. 61 , 69, 507 N.E.2d 1029 (1987). The right to be let alone promotes a "sense of security" in a free society "essential to liberty of thought, speech, and association." See id . at 73, 507 N.E.2d 1029 . By codifying this right in art. 14 and, later, the Fourth Amendment to the United States Constitution, our ancestors sought to "secure the privacies of life against arbitrary power," and "place obstacles in the way of a too permeating police surveillance" (quotations and citations omitted). Carpenter v. United States , --- U.S. ----, 138 S.Ct. 2206 , 2214, 201 L.Ed.2d 507 (2018). "[T]he relevant question is not whether criminals must bear the risk of warrantless surveillance, but whether it should be imposed on all members of society" (citation omitted). Blood , supra .

**54 The analysis regarding "which expectations of privacy are entitled to protection" is grounded in a historical understanding "of what was deemed an unreasonable search ... when [the Constitution] was adopted" (citation omitted). Carpenter , 138 S.Ct. at 2213-2214 . Our task is to "assure [the] preservation of that degree of privacy against government that existed when the Fourth Amendment [and art. 14 were] adopted." Id . at 2214 , quoting Kyllo v. United States , 533 U.S. 27 , 34, 121 S.Ct. 2038 , 150 L.Ed.2d 94 (2001). To do so, I *1201 would focus on the reasonable expectation of privacy that individuals maintain in their real-time location.

Individuals maintain a strong privacy interest in their location information, which implicates their private spheres. See Carpenter , 138 S.Ct. at 2217 (time-stamped location information from individual's cellular telephone "provides an intimate window into a person's life"). See also Riley v. California , 573 U.S. 373 , 403, 134 S.Ct. 2473 , 189 L.Ed.2d 430 (2014) (location records and other information on cellular telephones "hold for many Americans the privacies of life" [quotation and citation omitted] ). We thus have recognized the need to protect individuals' reasonable expectations of privacy in their location information:

"[T]he government's contemporaneous electronic monitoring of one's comings and goings in public places invades one's reasonable expectation of privacy. We conclude that under art. 14, a person may reasonably expect not to be subjected to extended [global positioning system (GPS) ] electronic surveillance by the government, targeted at his movements, without judicial oversight and a showing of probable cause."

Commonwealth v. Rousseau , 465 Mass. 372 , 382, 990 N.E.2d 543 (2013).

This interest is not diminished but, rather, heightened by the fact that most people carry cellular telephones with them at practically all times. See Riley , 573 U.S. at 395 , 134 S.Ct. 2473 ("it is the person who is not carrying a [cellular telephone] ... who is the exception. According to one poll, nearly three-quarters of smart phone users report being within five feet of their phones most of the time ..."). See also United States v. Ellis , 270 F.Supp.3d 1134 , 1145 (N.D. Cal. 2017) (cellular telephones act as close proxy to one's actual physical location). "We cannot accept the proposition that [cellular telephone] users volunteer to convey their location **55 information simply by choosing to activate and use their [cellular telephones] and to carry the devices on their person." United States v. Graham , 796 F.3d 332 , 355 (4th Cir. 2015), rehearing en banc, 824 F.3d 421 (4th Cir. 2016), cert. denied, --- U.S. ----, 138 S.Ct. 2700 , 201 L.Ed.2d 1096 (2018).

The ability of the government to know where anyone is at any moment poses a profound threat to the right to be let alone. A real-time ping permits police not merely to observe an individual's movements after the fact but to confront an individual wherever he or she may be. 1 When police act on real-time information by arriving at a person's location, they signal to both the individual and his or her associates that the person is being watched. "Awareness that the Government may be watching chills associational and expressive freedoms." See United States v. Jones , 565 U.S. 400 , 416, 132 S.Ct. 945 , 181 L.Ed.2d 911 (2012) (Sotomayor, J., concurring). To know that the government can find you, anywhere, at any time is -- in a word -- "creepy." United States v. Pineda-Moreno , 617 F.3d 1120 , 1126 (9th Cir. 2010) (Kozinski, J., dissenting), judgment vacated, 565 U.S. 1189 , 132 S.Ct. 1533 , 182 L.Ed.2d 151 (2012). "It is a power that places the liberty of every [person] in the *1202 hands of every petty officer" (citation omitted), Blood , 400 Mass. at 71 , 507 N.E.2d 1029 , and risks "alter[ing] the relationship between citizen and government in a way that is inimical to democratic society" (citation omitted), Jones , supra at 415-417, 132 S.Ct. 945 .

Other courts that have confronted this issue have done so by focusing on an individual's reasonable expectation of privacy in his or her real-time location. See, e.g., Matter of an Application of the U.S.A. for an Order Authorizing Disclosure of Location Info. of a Specified Wireless Tel ., 849 F.Supp.2d 526 , 583 (D. Md. 2011) ( Matter of an Application ) ("real time, precise location data generated by a [cellular telephone] is entitled to a reasonable expectation of privacy and thus is subject to the Fourth Amendment's protections"); State v. Andrews , 227 Md. App. 350 , 400, 134 A.3d 324 (2016) (defendant had reasonable expectation of privacy in real-time **56 cellular telephone location information). 2 This court, by contrast, puts undue emphasis on government "manipulation." Ante at note 13.

2. Search analysis . The court's reasoning risks conflating our doctrines of search and seizure. Although art. 14 and the Fourth Amendment guard against both, a search and a seizure are distinct legal concepts. See Commonwealth v. Connolly , 454 Mass. 808 , 819, 913 N.E.2d 356 (2009). Under both the Federal and Massachusetts Constitutions, the government conducts a search when it "intrudes on a person's reasonable expectation of privacy." Commonwealth v. Augustine , 467 Mass. 230 , 241, 4 N.E.3d 846 (2014), S . C ., 470 Mass. 837 , 26 N.E.3d 709 (2015), citing Katz v. United States , 389 U.S. 347 , 361, 88 S.Ct. 507 , 19 L.Ed.2d 576 (1967) (Harlan, J., concurring). See Carpenter , 138 S.Ct. at 2219 . The government conducts a seizure when it interferes with an individual's property rights. See Connolly , supra at 819, 823, 913 N.E.2d 356 . See also United States v. Karo , 468 U.S. 705 , 712, 104 S.Ct. 3296 , 82 L.Ed.2d 530 (1984). "The distinction is not merely academic." See Connolly , supra at 833, 913 N.E.2d 356 (Gants, J., concurring) (noting that attachment of GPS device to vehicle constituted search due to police's interference with owner's reasonable expectation of privacy, and not seizure).

The court appears preoccupied not with what the government learns when it conducts a ping, but with the way in which the government learns it. 3 In determining that *1203 the ping in this case constituted a search, the court puts substantial emphasis on the **57 fact that the government "secretly manipulate[d]" the defendant's cellular telephone by "initiat[ing] and effectively control[ing]" its transmission of a signal. See ante at ----, 120 N.E.3d 1183. Article 14 is implicated, the court notes, wherever "the [cellular telephone]'s location information is generated as a direct result of the government's manipulation of an individual's [cellular telephone]." See ante at note 13. This analysis, however, is more apposite to discussions of unreasonable seizure. Whether the ping constituted a search turns not on government manipulation but, rather, on reasonable expectations of privacy.

a. Seizure . In Connolly , 454 Mass. at 822-823 , 913 N.E.2d 356 , we confronted for the first time the issue of GPS monitoring by police. There, police had installed a GPS tracking device on a defendant's vehicle. Id . at 811, 913 N.E.2d 356 . By manipulating the defendant's property (the battery in his vehicle), the government was able to monitor his location. Id . at 812, 913 N.E.2d 356 .

We determined that the installation of the GPS tracking device constituted a seizure, because it required "entry by the police" into the defendant's vehicle and "operation of the vehicle's electrical system." Connolly , 454 Mass. at 822 , 913 N.E.2d 356 . We further determined that police monitoring of the device, "[i]n addition, and apart from the installation of the GPS device," independently constituted a second seizure:

"[T]he government's control and use of the defendant's vehicle to track its movements interferes with the defendant's interest in the vehicle notwithstanding that he maintains possession of it. The owner of property has a right to exclude it from 'all the world,' and the police use 'infringes that exclusionary right.' The interference occurs regardless whether the device draws power from the vehicle and regardless whether the data is transmitted to a monitoring computer. It is a seizure not by virtue of the technology employed, but because **58 the police use private property (the vehicle) to obtain information for their own purposes." (Citations omitted).

Id . at 823, 913 N.E.2d 356 .

Accordingly, where police "manipulate" private property (here, a cellular telephone), causing it to transmit information "for their own purposes," a seizure has occurred. Without using the vocabulary of "seizure" or "property," the court nonetheless performs an analysis steeped in both. In this case, however, the defendant did not challenge the ping of his cellular telephone as a seizure. The issue properly before us is only whether the ping constituted a search.

b. Search . Whether a search took place is a question of privacy rights, not property rights. See Connolly , 454 Mass. at 833 , 913 N.E.2d 356 (Gants, J., concurring) ("In fact, the appropriate constitutional concern *1204 is not the protection of property but rather the protection of the reasonable expectation of privacy").

The court cites Commonwealth v. One 1985 Ford Thunderbird Auto ., 416 Mass. 603 , 607, 624 N.E.2d 547 (1993), to justify its evaluation of the "nature of the intrusion" to determine whether the government violated a reasonable expectation of privacy. In its subsequent jurisprudence, however, this court, like the Federal courts, has moved beyond this narrow approach. See Augustine , 467 Mass. at 246 , 4 N.E.3d 846 (focusing on defendant's reasonable expectation of privacy in cell site location information [CSLI] itself); Commonwealth . v. Williams , 453 Mass. 203 , 208, 900 N.E.2d 871 (2009) (focusing on factors not involving government's intrusion 4 to determine whether defendant had reasonable expectation of privacy). See also Kyllo , 533 U.S. at 34 , 121 S.Ct. 2038 (declining to examine nature of intrusion in determining whether search had occurred). Our evaluation of an individual's reasonable expectation of privacy takes place "even in the absence of a property interest." See Rousseau , 465 Mass. at 382 , 990 N.E.2d 543 ("our property-based analysis in Connolly " does not represent "the outer limits of the protections afforded by art. 14").

Numerous searches involve no government manipulation of a person's property. Individuals maintain a reasonable expectation **59 of privacy, for example, where police wiretap a public telephone booth, see Katz , 389 U.S. at 348, 351 , 88 S.Ct. 507 ; monitor a GPS "beeper" in a private residence, see Karo , 468 U.S. at 707, 715 , 104 S.Ct. 3296 ; or penetrate the walls of a home with thermal sensors, see Kyllo , 533 U.S. at 29-30, 34 , 121 S.Ct. 2038 , all without manipulating an individual's property.

We have not required the manipulation of a cellular telephone in order to conclude that reasonable expectations of privacy in its historical location data are implicated. See Augustine , 467 Mass. at 250 , 4 N.E.3d 846 (police obtained historical CSLI from cellular service provider, without manipulating device). See also Carpenter , 138 S.Ct. at 2217 . A search occurs, for purposes of art. 14, whenever the police obtain an individual's real-time location via his or her cellular telephone, regardless of whether they do so by "manipulating" the device.

By focusing on government manipulation in the search analysis, even without using the word "seizure," the court risks confusing the issue, creating the impression that an exception exists for searches of real-time locations that providers collect automatically. If government manipulation were required in order to render a ping subject to art. 14 scrutiny, then police could side-step the constitutional protection by requesting not a ping, but, rather, the cellular service provider's own automatically generated record of a cellular telephone's current location. 5 Such an attempt *1205 might avoid manipulating the cellular telephone, but it leaves individuals vulnerable to police surveillance of their real-time (up to several seconds old), automatically collected location data. See Commonwealth v. Estabrook , 472 Mass. 852 , 858 n.12, 38 N.E.3d 231 (2015) (no exception for historical registration CSLI); Augustine , 467 Mass. at 255 , 4 N.E.3d 846 (reasonable expectation of privacy in historical CSLI). It is in obtaining an individual's real-time location information that the government interferes with his or her reasonable **60 expectation of privacy -- and thereby conducts a search. Such a search, however accomplished, exceeds the level of intrusion which society is willing to accept from its government.

3. Sanctity of the home . The court departs from the approach of other States to have confronted this issue in its silence concerning the risks of intruding upon private spaces, including the home. See, e.g., Tracey v. State , 152 So.3d 504 , 524-526 (Fla. 2014) (applying Fourth Amendment analysis); State v. Earls , 214 N.J. 564 , 568-569, 70 A.3d 630 (2013) (applying State constitution). See also Andrews , 227 Md. App. at 393 , 134 A.3d 324 (applying Fourth Amendment). I would rely, in part, on this reasoning, because it underscores significant risks inherent in the government pinging of cellular telephones.

In evaluating reasonable expectations of privacy in new contexts, we have long looked to whether an intrusion implicates a constitutionally protected area, such as the home. 6 See Kyllo , 533 U.S. at 29-30, 34 , 121 S.Ct. 2038 (reasonable expectation of privacy where police used thermal imaging to detect heat through walls of house); Karo , 468 U.S. at 714-715 , 104 S.Ct. 3296 (GPS monitoring within home presumptively unreasonable); Augustine , 467 Mass. at 252-253 , 4 N.E.3d 846 (recognizing that fundamental privacy interest attached to person's home complicates Fourth Amendment and art. 14 analysis). "[T]he sanctity of the home is of central concern in jurisprudence concerning the Fourth Amendment ... and art. 14 ...." Commonwealth v. Tatum , 466 Mass. 45 , 56, 992 N.E.2d 987 , cert. denied, 571 U.S. 1113 , 134 S.Ct. 830 , 187 L.Ed.2d 691 (2013).

Under the Fourth Amendment and art. 14, " all details [in the home] are intimate details, because the entire area is held safe from prying government eyes" (emphasis in original). Augustine , 467 Mass. at 252 , 4 N.E.3d 846 , quoting Commonwealth v. Porter P ., 456 Mass. 254 , 260, 923 N.E.2d 36 (2010). Any intrusion into the home, "by even a fraction of an inch," is presumptively unreasonable (citation omitted). See Kyllo , 533 U.S. at 37 , 121 S.Ct. 2038 . Where technology permits police to learn "any information regarding the interior of a home that could not **61 otherwise have been obtained" without entering the home, constitutional protections are triggered. See ibr.US_Case_Law.Schema.Case_Body:v1" id="p1206" href="#p1206" data-label="1206" data-citation-index="1" class="page-label">*1206 id . at 34 , 121 S.Ct. 2038 . See also Karo , 468 U.S. at 716 , 104 S.Ct. 3296 (ability to detect "a particular article -- or a person, for that matter ... that has been withdrawn from public view would present far too serious a threat to privacy interests in the home to escape entirely some sort of [constitutional] oversight").

Where some details of the home may appear more intimate than others -- compare, for example, boiling an egg with walking around in a state of undress -- the United States Supreme Court has declined to "develop a jurisprudence specifying which home activities are 'intimate' and which are not." Kyllo , 533 U.S. at 38-39 , 121 S.Ct. 2038 . For example, in Kyllo , supra at 38 , 121 S.Ct. 2038 , the government was not permitted to learn "how warm -- or even how relatively warm -- [a defendant] was heating his residence." As the Court stated:

"The Government ... contends that the thermal imaging was constitutional because it did not 'detect private activities occurring in private areas' .... The Fourth Amendment's protection of the home has never been tied to measurement of the quality or quantity of information obtained. ... [T]here is certainly no exception to the warrant requirement for the officer who barely cracks open the front door and sees nothing but the nonintimate rug on the vestibule floor."

Id . at 37 , 121 S.Ct. 2038 . The constitutional analysis does not permit a weighing of the significance of the intrusion:

"While it is certainly possible to conclude from the videotape of the thermal imaging that occurred in [Kyllo] that no 'significant' compromise of the homeowner's privacy has occurred, we must take the long view, from the original meaning of the Fourth Amendment forward.... Where, as here, the Government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a 'search' and is presumptively unreasonable without a warrant."

Id . at 40 , 121 S.Ct. 2038 .

Although physical entry is the "chief evil against which the wording of the Fourth Amendment is directed," see Commonwealth v. Lopez , 458 Mass. 383 , 390, 937 N.E.2d 949 (2010), it is not the only **62 one. 7 Where "the Government surreptitiously employs an electronic device to obtain information that it could not have obtained by observation from outside," a warrant is required. Karo , 468 U.S. at 715 , 104 S.Ct. 3296 (revealing location of canister). See Kyllo , 533 U.S. at 34 , 121 S.Ct. 2038 (revealing internal temperature of house); Blood , 400 Mass. at 70 , 507 N.E.2d 1029 (revealing contents of verbal conversations). While monitoring via an electronic *1207 device may be "less intrusive than a full-scale search," it nonetheless "does reveal a critical fact about the interior of the premises that the Government is extremely interested in knowing and that it could not have otherwise obtained without a warrant," and requires a warrant. See Karo , supra .

In this case, the police looked inside a home, through the use of technology, and determined that the defendant, or at least his cellular telephone, was located there. By inputting the GPS coordinates obtained from the ping into modern mapping technology, there remains no question that the defendant was within a private residence when the police pinged his cellular telephone. The court acknowledges that the same GPS coordinates would, today, "pinpoint the [cellular telephone]'s location to directly inside of the defendant's former girlfriend's home." See ante at note 16. This is information "that could not otherwise have been obtained" without entering the home. See Kyllo , 533 U.S. at 34 , 121 S.Ct. 2038 . See also Andrews , 227 Md. App. at 359, 378, 391 , 134 A.3d 324 (warrant required because signal "did reveal at least one critical detail about the residence; i.e., that its contents included [the defendant's cellular telephone], and therefore, most likely [the defendant] himself").

The court mistakenly looks to police knowledge of whether **63 their search intruded upon a home. 8 The court states that, had the capability to associate the defendant's GPS coordinates with "the defendant's presence inside of a home" "existed at the time the ping occurred in this case," a search would have occurred. See ante at note 16. This reasoning misses the mark. The inquiry is not whether the police appreciated that they were searching a home, but rather whether the police obtained information concealed within a home. 9 Here, they did: the defendant's location. Even if they only learned the name of the street, that information came from the cellular telephone within the home.

Of course, police cannot know in advance whether a ping will locate a suspect in a private residence. See Matter of an Application , 849 F.Supp.2d at 540-541 . "[C]ell phones ... blur the historical distinction between public and private areas because *1208 [they] emit signals from both places." Earls , 214 N.J. at 586 , 70 A.3d 630 . See United States v. Caraballo , 963 F.Supp.2d 341 , 354 (D. Vt. 2013), aff'd, 831 F.3d 95 (2d Cir. 2016), cert. denied, --- U.S. ----, 137 S.Ct. 654 , 196 L.Ed.2d 546 (2017) (defendant's presence on public highway during ping did not remove expectation of privacy, because location information would have been transmitted regardless of whether defendant was in his home or in public). As the Florida Supreme Court has **64 observed, the "warrant requirement cannot protect citizens' privacy if a court determines whether a warrant is required only after the search has occurred, and the incursion into a citizen's private affairs has already taken place." Tracey , 152 So.3d at 519 , quoting Commonwealth v. Pitt , Mass. Super. Ct., No. 2010-0061, 2012 WL 927095 (Norfolk County Feb. 23, 2012). Where the warrant analysis is performed "retrospectively based on the fact that the search resulted in locating the [cellular telephone] inside a home," the law "would provide neither guidance nor deterrence" to the officers. See Andrews , 227 Md. App. at 394 , 134 A.3d 324 .

"Accordingly, there is value in adopting a bright-line rule ...." Estabrook , 472 Mass. at 858 n.11, 38 N.E.3d 231 . See Kyllo , 533 U.S. at 38-39 , 121 S.Ct. 2038 (finding it impractical to bar thermal imaging of only "intimate details" because police do not "know in advance" what they will find). "[P]olice, trial judges, prosecutors, and defense counsel are entitled to as clear a rule as possible" regarding whether a real-time ping may be requested without a warrant (citation omitted). Estabrook , supra . By requiring a warrant before conducting a ping, in all cases, we avoid these warrantless intrusions into the home.

4. Exigent circumstances . I concur in the court's conclusion that, although the ping of the defendant's cellular telephone constituted a search, police were exempted from the warrant requirement in this case, due to exigent circumstances. It is important to note that the fact that the suspect shot an individual with a firearm did not, by itself, create an exigency. We repeatedly have "rejected the proposition that 'exigent circumstances always justify a warrantless entry and search in the aftermath of a crime involving a firearm.' " Commonwealth v. Figueroa , 468 Mass. 204 , 213, 9 N.E.3d 812 (2014), quoting Commonwealth v. Tyree , 455 Mass. 676 , 684, 919 N.E.2d 660 (2010). 10 Here, however, the suspect was still at large, in possession of a sawed-off shotgun; he had demonstrated his willingness **65 to use that weapon in front of witnesses; he had targeted an apparent stranger; he did not appear to have been provoked; and he had committed the offense in broad daylight. The Commonwealth introduced evidence that the officers were concerned about the ongoing danger to the safety of others posed by the *1209 defendant's continued retention of the sawed-off shotgun, and noted this concern on the form that they sent by facsimile to the cellular service provider. Given this, I agree that the order allowing the defendant's motion to suppress must be reversed.

5. Conclusion . Today, Massachusetts joins other States, as well as the majority of Federal courts to have addressed this issue, 11 in determining that, before police may demand to know where someone is by means of a cellular telephone, they must first obtain a warrant supported by probable cause. The detection of an individual's real-time location, by means of a cellular telephone, violates the individual's reasonable expectation of privacy. It is unnecessary for the court to rely upon the fact that the government manipulated a cellular telephone in this case in order to reach this conclusion.

New technologies hold great promise for helping to solve modern crimes. Doubtless, we will continue to develop increasingly advanced tools to aid law enforcement in the years to come. But as our capacity for surveillance grows, we must be mindful to preserve individuals' constitutional rights. We must be wary of the "all-powerful government, proclaiming law and order, efficiency, and other benign purposes," when it seeks to "penetrate all the walls and doors" behind which we might shelter. United States v. White , 401 U.S. 745 , 756, 91 S.Ct. 1122 , 28 L.Ed.2d 453 (1971) (Douglas, J., dissenting). There must always be judicial oversight interposed between the government and the individual it seeks to observe, lest we allow the guarantees of privacy **66 to slip away -- not because we no longer needed them, but because we left them behind in our rush toward progress.

GANTS, C.J. (concurring, with whom Gaziano and Lowy, JJ., join).

I agree with the court's conclusion that a warrant is required to search the real-time location of an individual's cellular telephone (cell phone). I also agree that, under the exigent circumstances exception to the search warrant requirement, the police in this case could lawfully obtain the assistance of the cellular company to "ping" the defendant's cell phone -- without prior judicial authorization -- because time was of the essence to determine his location in order to arrest him for the brutal killing. I write separately only because this case highlights the need for Massachusetts to join the majority of other States in allowing warrants to be obtained by telephone or other reliable electronic means so that, in the future, a warrant can reasonably be obtained promptly where time is of the essence.

In 1973, before the widespread use of cell phones, cell site location information, global positioning systems installed in cell phones, and electronic mail messages (e-mail), the National Advisory Commission on Criminal Justice Standards and Goals recommended that "every State enact *1210 legislation that provides for the issuance of search warrants pursuant to telephoned petitions and affidavits from police officers." National Advisory Commission on Criminal Justice Standards and Goals, Report on Police 95 (1973) (noting that "[l]engthy delays in obtaining search warrants are the chief reason that police officers rely upon exceptions to the rule requiring warrants"). See American Bar Association Project on Standards for Criminal Justice, Standards Relating to the Urban Police Function 257 (Mar. 1972) (highlighting "the time and effort required to obtain a search warrant ... [because of] the frequent unavailability of the magistrate," and recommending that "new procedures ... be devised to simplify the warrant process"). Since then, advances in technology have enabled police officers to apply for warrants remotely -- that is, without physically appearing before a judge or magistrate -- through a variety of means other than a telephone, including e-mail and video conferencing. See Missouri v. McNeely , 569 U.S. 141 , 154, 133 S.Ct. 1552 , 185 L.Ed.2d 696 (2013). In 2013, the United States Supreme Court identified thirty-six States that permit remote warrant applications in at least some circumstances. **67 Id . at 154 n.4, 133 S.Ct. 1552 . 1 Since the McNeely opinion was issued, at least six more States have enacted statutes or procedural rules permitting remote search or arrest warrant applications. 2 Moreover, the Federal Rules of Criminal Procedure permit Federal magistrate judges to consider sworn information that is provided in support of a search warrant or an arrest warrant application "by telephone or other reliable electronic means," and to transmit to the applicant the approved warrant by those same means. See Fed. R. Crim. P. 4.1 ; Fed. R. Crim. P. 41(d)(3).

No comparable rule of criminal procedure can be promulgated in Massachusetts by this court, however, because G. L. c. 276, § 2B, provides that "[a] person seeking a search warrant shall appear personally before a court or justice authorized to issue search warrants in criminal cases and shall give an affidavit in substantially the form hereinafter prescribed" (emphasis added). We have permitted a law enforcement officer to obtain a search warrant by telephone or facsimile transmission only where "the officer exhausted all reasonable *1211 efforts to find a judge before whom he could personally appear." Commonwealth v. Nelson , 460 Mass. 564 , 573, 953 N.E.2d 164 (2011). In all other circumstances, our law requires officers to find and personally appear before a magistrate or judge. Id . at 569-570, 953 N.E.2d 164 .

In determining whether the exigency exception to the search warrant requirement justifies the failure of the police to obtain **68 prior judicial approval of a search, we consider the amount of time necessary to obtain a warrant. See Commonwealth v. Tyree , 455 Mass. 676 , 690-691, 919 N.E.2d 660 (2010) ("In evaluating whether exigent circumstances existed, we also have placed particular emphasis on whether police consider[ed] how long it would take to obtain a warrant before acting" [quotation and citation omitted] ); Commonwealth v. Forde , 367 Mass. 798 , 801-803, 329 N.E.2d 717 (1975). Where time is of the essence, as it often is when law enforcement seeks to ping a cell phone to determine a suspect's location, the more time that is needed to obtain a warrant, the greater the need for law enforcement to invoke the exigency exception. The length of time required to obtain a warrant depends on the length of three time periods: (1) the time needed to write an affidavit and particularize an application and warrant, (2) the time needed to locate a judge or magistrate (or reasonably exhaust efforts to locate him or her), and (3) the time needed to appear before the magistrate or judge and obtain his or her signature. The second and third time periods could be considerably shortened, especially when the court house is closed, if Massachusetts were to join the Federal government and at least forty-two States in allowing warrants to be approved by reliable electronic means. See McNeely , 569 U.S. at 172-173 , 133 S.Ct. 1552 (Roberts, C.J., concurring in part and dissenting in part) (noting that in Utah, under State electronic search warrant procedure, "[j]udges have been known to issue warrants in as little as five minutes").

Today, modern technology can be applied to enable substantially quicker electronic application procedures that satisfy the requirements of art. 14 of the Massachusetts Declaration of Rights and the Fourth Amendment to the United States Constitution. In California, for example, the statutory scheme explicitly provides that a magistrate may receive an officer's affidavit via e-mail with an electronic signature, and then issue the warrant with an electronic signature and transmit it back via e-mail; this document is considered the original warrant. See Cal. Penal Code § 1526 (b). Moreover, if a magistrate wishes to see the affiant raise his or her right hand to swear to the truth of the affidavit, the magistrate may use face-to-face video technology -- such as Skype or FaceTime software -- in the issuance of warrants. See Bean, Swearing by New Technology: Strengthening the Fourth Amendment by Utilizing Modern Warrant Technology While Satisfying the Oath or Affirmation Clause, 2014 B.Y.U. L. Rev. 927, 945-946.

The court in its decision recognizes that law enforcement, after properly obtaining a warrant or facing exigent circumstances, may **69 employ Twenty-first Century technologies to solve Twenty-first Century crimes. But requiring officers to locate and then personally appear before a judge or magistrate when the court house is closed -- or when the affiant is far away from the judge or magistrate -- is hardly a Twenty-first Century procedure. I believe that our opinion today underscores the need for the Legislature to give careful consideration to amending G. L. c. 276, § 2B, to permit warrants to be applied for and approved remotely through reliable electronic means *1212 so that judicial approval may be sought and obtained in a timely manner.