Court Opinion

ID: 9942085
Source: CourtListenerOpinion
Date Created: 2024-02-20 15:06:14.749362+00
Date Added: 2024-06-11T13:47:40.288061
License: Public Domain

NOTICE: All slip opinions and orders are subject to formal
revision and are superseded by the advance sheets and bound
volumes of the Official Reports. If you find a typographical
error or other formal error, please notify the Reporter of
Decisions, Supreme Judicial Court, John Adams Courthouse, 1
Pemberton Square, Suite 2500, Boston, MA, 02108-1750; (617) 557-
1030; SJCReporter@sjc.state.ma.us

SJC-13499

                COMMONWEALTH     vs.   VICTOR ARRINGTON.

         Suffolk.       December 6, 2023. - February 20, 2024.

     Present:       Budd, C.J., Gaziano, Lowy, Kafker, Wendlandt,
                              & Georges, JJ.1

Cellular Telephone. Practice, Criminal, Motion in limine,
     Interlocutory appeal, Appeal by Commonwealth, Presumptions
     and burden of proof. Evidence, Expert opinion, Scientific
     test, Presumptions and burden of proof. Witness, Expert.
     Rules of Criminal Procedure.

     Civil action commenced in the Supreme Judicial Court for
the county of Suffolk on September 13, 2023.

     The case was reported by Kafker, J.

     Ian MacLean, Assistant District Attorney (Edmond J. Zabin,
Assistant District Attorney, also present) for the Commonwealth.
     Michelle Menken (E. Peter Parker also present) for the
respondent.
     The following submitted briefs for amici curiae:
     Jessica Hyde & Eoghan Casey, pro se.
     Patrick Levin, Committee for Public Counsel Services, for
Committee for Public Counsel Services.
     Dan Loper, Karl Epps, & Steven Verronneau, pro se.

     1 Justice Lowy participated in the deliberation on this case
and authored his concurrence prior to his retirement.
                                                                    2

     Jennifer Stisa Granick & Andrew Crocker, of California,
Michael W. Price & Hannah Zhao, of New York, Jessica J. Lewis,
Jessie J. Rossman, Daniel K. Gelb, Nathan Freed Wessler, &
Chauncey B. Wood for American Civil Liberties Union & others.

     KAFKER, J.   The Commonwealth alleges that in March of 2015,

the defendant, Victor Arrington, and two others broke into a

home, killed one resident, grievously wounded another, and

attempted to set fire to the home.2   Prosecuting the defendant

for murder in the first degree and other crimes related to the

home invasion,3 the Commonwealth moved in limine to permit the

introduction at trial of frequent location history (FLH) data

retrieved from the defendant's cell phone, an Apple iPhone 6.4

The Commonwealth contends that expert testimony regarding the

FLH data would establish that the defendant's cell phone was in

the immediate vicinity of the crime scene at the time the crime

was committed.    Because FLH data has never been admitted as

     2 Although this case comes to us on a reservation and report
by a single justice of the Commonwealth's petition pursuant to
G. L. c. 211, § 3, for convenience, we refer to Victor Arrington
as the "defendant," rather than the "respondent."

     3 The defendant was also charged with home invasion, two
counts of kidnapping, arson of a dwelling house, armed assault
with intent to murder, and possession of a firearm without a
license.

     4 FLH data are generated from location data points saved on
an iPhone using a proprietary algorithm to identify locations
that a user has visited several times. See part 1.b, infra.
The Commonwealth contends that FLH data reliably provide an
approximate location for the cell phone for a particular time.
                                                                     3

evidence in any court in the Commonwealth, or apparently in any

other jurisdiction in the country, the trial judge held a three-

day evidentiary hearing to determine whether the Commonwealth's

proffered expert testimony on FLH data would be permitted.     The

trial judge denied the Commonwealth's motion, and the

Commonwealth sought appellate review.

     As a preliminary issue, the parties disagree as to whether

the Commonwealth may appeal from the denial of its motion to

admit expert testimony under Mass. R. Crim. P. 15 (a) (2), as

appearing in 474 Mass. 1501 (2016) (rule 15 [a] [2]), or whether

its sole avenue for interlocutory review is a petition under

G. L. c. 211, § 3.   On the merits, the Commonwealth contends

that the trial judge abused his discretion in denying its motion

on Daubert-Lanigan grounds.    See Daubert v. Merrell Dow Pharms.,

Inc., 509 U.S. 579, 585-595 (1993); Commonwealth v. Lanigan, 419

Mass. 15, 25-26 (1994).    Both issues were presented to a single

justice of this court, who reserved and reported the case to the

full court.

     As to the procedural question, rule 15 (a) (2) does not

give the Commonwealth the ability to apply for leave to appeal

from the denial of a motion in limine where, as here, the

ruling, if allowed to stand, does not, "as a practical matter,

. . . terminate the prosecution."    Commonwealth v. Anderson, 401

Mass. 133, 135 (1987).    Instead, in such situations, the
                                                                       4

appropriate avenue for the Commonwealth to seek interlocutory

review of a ruling on a motion in limine is through a petition

under G. L. c. 211, § 3.      Turning to the merits of the

Commonwealth's petition here, we discern no abuse of discretion

by the trial judge in denying the Commonwealth's motion to admit

the proffered expert testimony on FLH data.      Accordingly, we

affirm.5

     1.    Background.   a.   Facts.   As trial has yet to begin, we

summarize the evidence the Commonwealth has stated it expects to

introduce at trial.      See Commonwealth v. Spencer, 465 Mass. 32,

33 (2013).    We reserve certain facts for our discussion of the

merits of the Commonwealth's motion to admit FLH evidence.

     The Commonwealth alleges that at around 10:51 A.M. on March

31, 2015, the defendant, a cooperating witness, and Jeromie

Johnson6 participated in a home invasion on Harvard Street in the

Dorchester section of Boston.      Richard Long, Yvette O'Brien, and

O'Brien's newborn son were at home at the time of the attack.

     5 We acknowledge the amicus briefs submitted by the American
Civil Liberties Union, the American Civil Liberties Union of
Massachusetts, Inc., the Massachusetts Association of Criminal
Defense Lawyers, the National Association of Criminal Defense
Lawyers, Inc., and the Electronic Frontier Foundation; the
Committee for Public Council Services; Jessica Hyde and Eoghan
Casey; and Dan Loper, Karl Epps, and Steven Verronneau.

     6 Johnson was killed about a week after the home invasion at
issue here, and thus is not a codefendant in this case.
                                                                      5

Johnson and the defendant bound Long and O'Brien with electrical

cords, cut Long with a knife, and shot both Long and O'Brien in

the head.    They then set fire to the house.   Long died from his

wounds.     O'Brien survived the gunshot wound and can describe the

events that occurred in the apartment until she was shot in the

head, but she is unable to identify the perpetrators.     The

cooperating witness agreed to testify against the defendant in

exchange for facing reduced charges.    The Commonwealth asserts

that the cooperating witness will identify the perpetrators and

their roles in the home invasion and associated crimes.

     The defendant allegedly drove to the crime scene in a white

sedan rented by his girlfriend for his use.     The defendant's car

was captured on video being driven down Blue Hill Avenue in

Dorchester, with another car carrying Johnson and the

cooperating witness following behind.    The defendant's car was

next seen parked on Paxton Street near the scene of the crime.

At 10:44 A.M., the defendant received a call from Johnson

lasting over three minutes, and the defendant called Johnson

several times over the next few minutes with no answer.    The

defendant's telephone utilized a cell tower the coverage area of

which included the crime scene for these calls.7    A video camera

at a Department of Youth Services facility located across the

     7   The defendant's cell phone was seized on April 8, 2015.
                                                                      6

street from the crime scene captured grainy video footage of two

people approaching the victims' home at 10:51 A.M., and the same

video camera captured footage of three people leaving at 11:20

A.M.       The defendant's car was captured on video at 11:22 A.M.

being driven down Blue Hill Avenue.

       b.    Frequent location history data.   When turned on, an

iPhone generates location data points from sources such as

global positioning system (GPS) data, nearby wireless computer

network (Wi-Fi) access points, short-range wireless Bluetooth

connections, and cell site location information (CSLI).      These

location data points are stored on the iPhone's "Encrypted B"

cache8 for between twenty-four and forty-eight hours.      In 2015,

an algorithm on the iPhone would use these data points to create

FLH data.9      The FLH data created by the algorithm consist of a

       A cache is "a computer memory with very short access time
       8

used for storage of frequently or recently used instructions or
data." Merriam-Webster Online Dictionary, https://www.merriam-
webster.com/dictionary/cache [https://perma.cc/FFL2-EEP7].

       This information is referred to as "Significant Locations"
       9

on newer iPhone operating systems. Documents provided to
customers by Apple explain that "Significant Locations allows
iPhone, iPad, Apple Watch, and iCloud to learn the places that
are significant to a user in order to provide useful location-
related features and information in a way that Apple can't read.
Data collected about a significant location includes the address
the user travelled to, when they traveled there, how long they
stayed, the amount of time spent commuting to the location, the
method used to reach the location . . . , and the total number
of times the user has visited that place."
                                                                      7

longitude and latitude coordinate point and a circle around it,

representing an amalgamation of the location data points.     The

radius of the circle, labeled the "uncertainty" in the FLH data,

represents the approximate area in which the cell phone was

located.   The uncertainty radius can change from visit to visit

to a frequent location, as can the coordinate point representing

the center of the frequent location.     FLH data also provides an

estimated time that the iPhone entered the location, and an

estimated time the iPhone left the location.     The algorithm used

to convert location data points into FLH data is proprietary,

and thus the Commonwealth's expert did not have access to the

algorithm itself during his testing of FLH data reliability.

Moreover, it is unclear how the algorithm processes, or weighs,

the different location data points generated by the iPhone.

     In 2022, a full-file system extraction was performed on the

defendant's cell phone.     This extraction allowed the

Commonwealth to access encrypted files on the cell phone,

including its FLH data.10    The FLH data on the cell phone listed

345 frequent location visits.    Of particular interest to the

Commonwealth is frequent location no. 58.     Frequent location no.

58 is centered on coordinates corresponding to a Harvard Street

     10Although the FLH data for the date of the murder was
available on the defendant's cell phone, the underlying location
data that was used to produce the FLH data was no longer
available.
                                                                     8

address near the victims' home.    The uncertainty radius of

frequent location no. 58 is forty-three meters, or 143 feet,

which encompasses the crime scene.    The Commonwealth's proffered

expert on FLH data, a senior crime analyst in the office of the

district attorney for the Suffolk district (analyst), testified

that he interpreted the FLH data retrieved from the defendant's

cell phone to show that the phone entered the area represented

in frequent location no. 58 at 10:36 A.M. on March 31, 2015, and

left the area at 11:22 A.M that day.    The Commonwealth therefore

contends that the proffered expert testimony on FLH data, if

admitted, would corroborate the cooperating witness's testimony

placing the defendant at the scene of the home invasion.

     c.   Procedural background.   In April 2023, the Commonwealth

informed the judge that a Daubert-Lanigan hearing would be

needed to determine the admissibility of FLH data evidence

gathered from the defendant's cell phone.    In May, a Daubert-

Lanigan hearing was scheduled for July 27.    On July 26, the

Commonwealth requested a continuance, and the hearing was

continued to August 29.   Between June 16 and August 24, the

analyst performed experiments on a test iPhone to determine the

reliability of FLH data, with the majority of his experiments

performed between August 14 and 24.    The Daubert-Lanigan hearing

on the admissibility of FLH evidence was held on August 29,

September 7, and September 8, ending four days before the
                                                                    9

defendant's trial was scheduled to start on September 12.     The

analyst was the only witness who testified at the hearing.

     At the evidentiary hearing, the analyst testified regarding

his understanding of how FLH data are created.   Although the

analyst did not have access to the algorithm that generates FLH

data and could not testify as to how the algorithm converted

location data inputs into FLH data, he explained the tests he

had done to ascertain the reliability of FLH data in identifying

where a cell phone is located at a particular time.   The analyst

conducted tests of FLH data reliability using a "jailbroken"11

iPhone (test iPhone) that was similar, but not identical, to the

iPhone associated with the defendant.12   When pressed, the

analyst acknowledged that there were likely differences in the

FLH algorithms used by the two iPhones, and although he believed

that any changes were not significant, he could not say for

     11Jailbreaking is removing the built-in limitations from an
electronic device, such as a cell phone. Merriam-Webster Online
Dictionary, https://www.merriam-webster.com/dictionary/jailbreak
[https://perma.cc/7MR6-2LJ5]. The analyst jailbroke the iPhone
he used to test FLH data in order to access location data that
users normally cannot view.

     12The defendant's cell phone is an iPhone 6 running the iOS
8.1 operating system. The analyst used an iPhone 5C running the
iOS 8.4.1 operating system. The analyst performed the testing
using a different operating system from that found on the
defendant's cell phone because the code used to jailbreak iOS
8.4.1 is publicly available, whereas code to jailbreak iOS 8.1
is not. It is not clear why the analyst did not use an iPhone 6
in his experiments.
                                                                   10

sure.    The analyst conducted a total of twelve experiments using

the test iPhone at five different locations in Boston.

        The Commonwealth also provided evidence regarding five

locations that were identified as frequent locations on the

defendant's cell phone.    The analyst discussed additional data

retrieved from the defendant's cell phone that provided

corroborating evidence that the defendant's phone was near

locations corresponding with the frequent locations at the times

indicated by the FLH data.     The analyst's proposed expert

testimony would state, based on his interpretation of the FLH

data recovered from the defendant's cell phone, that between

10:36 A.M. and 11:22 A.M. on March 31, 2015, the defendant's

phone was within a 143-foot radius of a Harvard Street address

near the victims' home, an area that includes the scene of the

crime.

        On September 11, 2023, the trial judge denied the

Commonwealth's motion to permit the introduction of FLH evidence

at trial.    On the same day, the Commonwealth filed a notice of

appeal, believing that the notice of appeal would stay the trial

court proceedings pursuant to Mass. R. Crim. P. 15 (e), as

appearing in 474 Mass. 1501 (2016).     The defendant filed a

response, arguing that the Commonwealth's notice of appeal did

not automatically stay the trial court proceedings.

Specifically, the defendant argued that the appeal procedures in
                                                                     11

rule 15 were inapplicable, and that the Commonwealth's only

avenue for interlocutory review of the denial of a motion in

limine was a petition under G. L. c. 211, § 3, which, in turn,

did not automatically stay the trial court proceedings.     The

trial judge concluded that the Commonwealth's appeal was outside

the scope of rule 15, but nonetheless stayed the proceedings to

allow the Commonwealth to pursue relief through a G. L. c. 211,

§ 3, petition.   A single justice of this court then extended the

stay and subsequently reserved and reported the case to the full

court, including both the procedural question whether this

appeal was within the scope of rule 15 and the merits of whether

the trial judge abused his discretion in denying the

Commonwealth's motion to permit introduction of FLH data.

     2.   Discussion.   a.   Availability of appeal under rule

15 (a) (2).   As a preliminary matter, we must determine whether

the Commonwealth was entitled to appeal from the trial judge's

ruling under rule 15 (a) (2), or whether its procedural avenue

for relief must instead come from this court's superintendence

powers under G. L. c. 211, § 3.     The Commonwealth contends that

because the trial judge's ruling rejecting admission of expert

testimony regarding FLH data had the effect of preventing the

admission of "critical" evidence in its case against the

defendant, the ruling is the functional equivalent of a motion
                                                                   12

to suppress and thus entitles the Commonwealth to an appeal

under rule 15 (a) (2).   We disagree.

       We construe our rules of procedure according to the

ordinary canons of construction, beginning with the plain

meaning of the text.   Commonwealth v. Wright, 479 Mass. 124, 133

(2018).   The text of rule 15 (a) (2) provides for interlocutory

appeal from "an order determining a motion to suppress evidence

prior to trial."   By its express terms, rule 15 (a) (2) "does

not encompass other interlocutory rulings, in part for sound

reasons of judicial economy, as such 'ruling[s] [are] subject to

change when the case unfolds.'"    See Spencer, 465 Mass. at 40

n.11, quoting Luce v. United States, 469 U.S. 38, 41 (1984)).

       Although the text of rule 15 (a) (2) is directed only at

motions to suppress, we have allowed a narrow exception to this

general rule:   "if a motion to exclude all or most of the

Commonwealth's incriminating evidence is allowed, and if, as a

practical matter, that ruling (if permitted to stand) would

terminate the prosecution, the Commonwealth may seek leave to

appeal pursuant to [rule 15 (a) (2)]."    Anderson, 401 Mass. at

135.   This narrow exception to, or more precisely, expansion of,

rule 15 (a) (2) (Anderson expansion) recognizes that, in the

very limited subset of cases where a ruling on a motion in

limine to exclude evidence prevents the introduction of all or

most of the Commonwealth's evidence, preventing the opportunity
                                                                   13

for an interlocutory appeal could effectively preclude the

Commonwealth from continuing the prosecution of serious crimes

without any opportunity for appellate review.   See Commonwealth

v. Ruiz, 480 Mass. 683, 692 (2018) ("important jurisprudential

interests" are served by "the review of pretrial decisions that

terminate criminal proceedings prior to a trial being held").

     We have allowed this narrow expansion of the scope of rule

15 (a) (2) because we have concluded that rule 15 (a) (2) should

be read in the context of rule 15 as a whole, which allows

interlocutory appeals from orders that would otherwise terminate

a criminal proceeding.   See Mass. R. Crim. P. 15 (a) (1), as

appearing in 474 Mass. 1501 (2016) (allowing Commonwealth to

appeal following grant of motion to dismiss complaint or

indictment, or from "a motion for appropriate relief" made

pursuant to Mass. R. Crim. P. 13 [c], as appearing in 474 Mass.

1501 [2016]); Mass. R. Crim. P. 15 (a) (3), as appearing in 476

Mass. 1501 (2017) (Commonwealth may appeal from "a decision by a

judge discharging a person pursuant to G. L. c. 119, § 72A").

See also Ruiz, 480 Mass. at 692-693, quoting Burke v.

Commonwealth, 373 Mass. 157, 160 (1977) (appeal from trial

court's dismissal of indictment pursuant to rule 15 [a] [1]

"allow[s] the Commonwealth to reinstitute proceedings terminated

because of an incorrect ruling in the trial court, . . . but, on

the other hand, . . . allow[s] [appellate courts] to affirm
                                                                  14

preliminary rulings which, in effect, put an end to a particular

prosecution"); Commonwealth v. Yelle, 390 Mass. 678, 685 (1984)

(declining to consider pretrial motion to admit evidence as

"motion for appropriate relief" under rule 15 [a] [1] in part

because "[t]he allowance of a defendant's motion to admit

evidence does not, as the allowance of a motion to suppress so

often does in practical effect, terminate the proceedings").

Barring appeals in such situations could "leave a class of

cases, many of which involve serious crimes, lost either to

further prosecution or any appellate review."   Ruiz, supra at

693, quoting Burke, supra.    Indeed, rule 15 was adopted to

implement G. L. c. 278, § 28E, a statute intended to allow the

Commonwealth to appeal from rulings that would terminate

criminal proceedings.   See Yelle, supra, citing Burke, supra at

161 ("The Commonwealth's right to appeal from certain pretrial

rulings under G. L. c. 278, § 28E, is based on the fact that

those rulings preclude a public trial and entirely terminate the

proceedings").

     The Commonwealth suggests that rule 15 (a) (2) should be

interpreted more broadly to encompass other situations where

"critical" evidence is excluded, even where the evidence

excluded does not have the practical effect of terminating the

criminal proceeding.    The Commonwealth thus proposes that,

although the exclusion of its expert's testimony does not
                                                                    15

prevent it from introducing all or most of its incriminating

evidence at trial, the instant appeal is properly brought under

rule 15 (a) (2) because the expert's testimony regarding FLH

data is "critical" to the case against the defendant.

     Because its case at trial will rely significantly on

testimony by a cooperating witness procured in exchange for a

reduced sentence, we agree with the Commonwealth that evidence

corroborating the cooperating witness's testimony (and, thus,

bolstering the credibility of that testimony) might fairly be

described as "critical" to the prosecution's case.   Nonetheless,

we decline the Commonwealth's invitation to expand the scope of

rule 15 (a) (2) to include the ruling on the motion in limine in

the instant case.   The plain text of rule 15 (a) (2) refers only

to motions to suppress and thus sets out the general rule.     As

discussed supra, however, the purpose of rule 15 is to provide

an avenue for interlocutory review of rulings that would

otherwise terminate a criminal proceeding.   Thus, the narrow

Anderson expansion that we have allowed is consonant with this

purpose because it expands rule 15 (a) (2) only to include

motions in limine that exclude so much incriminating evidence

that the motion effectively forecloses the Commonwealth's

ability to prosecute its case at trial.   See Anderson, 401 Mass.

at 135.
                                                                  16

     We have also previously observed that further expanding the

availability of interlocutory appeals pursuant to rule 15 would

create the potential for delay and disruption in criminal

proceedings.   See Ruiz, 480 Mass. at 694 ("an unrestrained right

to pretrial appeals by the Commonwealth may be burdensome on

defendants [and the courts]"); Yelle, 390 Mass. at 687 (to allow

Commonwealth right to interlocutory review from every adverse

evidentiary ruling "would be to create a potential for

disruption of every criminal trial where a disgruntled

prosecutor could cause the stay of the proceeding, pending

appellate review of evidentiary rulings").   See also

Commonwealth v. Cavanaugh, 366 Mass. 277, 279 (1974)

("interlocutory appeals and reports should not be permitted to

become additional causes of the delays in criminal trials which

are already too prevalent").13

     13Under Mass. R. Crim. P. 15 (e), criminal proceedings are
automatically stayed for thirty days following a ruling subject
to rule 15's interlocutory procedures. If, as the Commonwealth
urges, rule 15 (a) (2) were expanded to allow appeals from
rulings on motions in limine that exclude "critical" evidence,
rulings on such motions would automatically stay proceedings to
give the Commonwealth time to consider whether to appeal, which
would invariably lead to delays in criminal proceedings. See
Yelle, 390 Mass. at 687. Moreover, as in this case, there would
likely be further delay occasioned by disagreements between the
parties as to whether excluded evidence was "critical." We note
that in the present case, the trial judge decided the motion in
limine on the admissibility of the Commonwealth's proffered
expert testimony the day before the scheduled start of trial.
The interlocutory appellate proceedings in this matter have thus
occasioned significant delay to the anticipated start of trial.
                                                                     17

     The Commonwealth contends nonetheless that in our case law

following Anderson, we have expanded the circumstances in which

the Commonwealth may use rule 15 (a) (2) to appeal from motions

in limine beyond those that effectively foreclose the

Commonwealth's ability to prosecute its case at trial.         The

Commonwealth's contention relies in part on this court's

decision in Spencer, 465 Mass. 32, which it suggests stands for

the proposition that the exclusion of "critical" evidence is

sufficient to allow the Commonwealth to request leave to appeal

under rule 15 (a) (2).

     In Spencer, 465 Mass. at 40, the Commonwealth filed an

emergency petition for extraordinary relief pursuant to G. L.

c. 211, § 3, arguing that motions in limine "sought to exclude

most of the Commonwealth's incriminating evidence."      The

Commonwealth represented that the evidence excluded by the

judge's preliminary rulings was "critical to establish[ing]

identity, motive, and consciousness of guilt."   Id. at 44.

After presenting its arguments before a single justice, "the

single justice granted the petition for extraordinary relief,

ordered that proceedings in the Superior Court be stayed, and

ordered the Commonwealth to file an interlocutory appeal" under

rule 15 (a) (2).   Id. at 40.   "The single justice then allowed

the appeal to proceed before this court."   Id. at 41.
                                                                   18

     In Spencer, the parties did not challenge the single

justice's order to file an appeal under rule 15 (a) (2), so we

did not address whether it was appropriate for the Commonwealth

to proceed under rule 15.14    See id. at 40-41.   However, in

discerning no error in the trial judge's rulings, we did

observe, after a more thorough examination of the record, that

"[e]ven had the judge allowed the defendant's motion to exclude

the recordings in their entirety, the Commonwealth would still

have ample evidence upon which to proceed to trial."     Id. at 45.

Indeed, we expressly stated:    "Were the judge's preliminary

rulings . . . permitted to stand, it would not as a practical

matter [have] 'terminate[d] the prosecution.'"     Id., quoting

Anderson, 401 Mass. at 133.    We therefore do not understand

Spencer to be an endorsement of the proposition that the

exclusion of "critical" evidence before a trial is sufficient

for the Commonwealth to avail itself of an interlocutory appeal

under rule 15 (a) (2).   Compare Spencer, supra at 43 (assertion

     14Similarly, in Commonwealth v. Beausoleil, 397 Mass. 206,
207-208 (1986), a single justice of this court chose to treat a
petition under G. L. c. 211, § 3, challenging the exclusion of
evidence, as an appeal from a motion to suppress under rule
15 (a) (2). On appeal before this court, the parties did not
challenge the single justice's decision, so we did not address
the issue. See id. at 208 n.2. To the extent our decision in
Beausoleil has been read to support a further expansion of rule
15 beyond the narrow Anderson expansion, such a reading is
incorrect. The correctness of the single justice's consideration
of the exclusion of evidence as a rule 15 motion was not raised
and not decided.
                                                                  19

"that the excluded recordings comprise[d] 'most of the

Commonwealth's evidence' . . . [did] not withstand close

scrutiny of the record"), with Anderson, supra at 135 ("if a

motion to exclude all or most of the Commonwealth's

incriminating evidence is allowed, and if, as a practical

matter, that ruling [if permitted to stand] would terminate the

prosecution, the Commonwealth may seek leave to appeal pursuant

to [rule 15 (a) (2)]").   Rather, in Spencer, supra at 43-44, we

implicitly disapproved of the Commonwealth having the

opportunity for an interlocutory appeal under rule 15 (a) (2)

where excluded evidence did not effectively terminate the

prosecution.   We therefore clarify here that any reading of

Spencer suggesting that the exclusion of "critical" evidence

alone is sufficient to allow the Commonwealth to apply for leave

to appeal under rule 15 (a) (2) is incorrect.   See Anderson,

supra; Mass. R. Crim. P. 15 (a) (2).15

     15Our discussion of rule 15 (a) (2) in Commonwealth v.
Fontanez, 482 Mass. 22 (2019), and the cases cited therein,
similarly does not support the Commonwealth's reading of rule
15. See id. at 23 n.1, 26 (Commonwealth could have filed for
leave to appeal under rule 15 [a] [2] where "the judge's
decision to exclude the now deceased victim's testimony
effectively foreclose[d] the Commonwealth's ability to prosecute
a serious crime"). See also Commonwealth v. Arrington, 455
Mass. 437, 437-438 (2009) (Commonwealth appealed under rule
15 [a] [2] from order excluding prior recorded testimony of
deceased victim, only eyewitness to crime); Commonwealth v.
Gonsalves, 445 Mass. 1, 15 (2005), cert. denied, 548 U.S. 926
(2006), abrogated on other grounds as recognized by Commonwealth
v. Rand, 487 Mass. 811, 825 n.14 (2021) (judge's order excluding
                                                                  20

        In the present case, it is undisputed that the FLH data

evidence does not constitute "all or most of the Commonwealth's

incriminating evidence."    See Anderson, 401 Mass. at 135.

Indeed, the Commonwealth plans to have eyewitness testimony from

its cooperating witness placing the defendant at the scene of

the crime and describing his role in the murder and other

crimes.     The Commonwealth also intends to introduce video

recordings showing that a vehicle matching the description of

the vehicle rented for the defendant was in the area of the

victims' home prior to the crime and left the area after three

figures were recorded leaving the crime scene.    Furthermore,

CSLI data will show that the defendant's cell phone was in the

area of the victim's home during the relevant time frame as

well.     Because this case does not involve the determination of a

motion to suppress, and because the exclusion of the FLH data

will not, as a practical matter, terminate the Commonwealth's

prosecution, the instant appeal is outside the scope of rule

15 (a) (2) and the narrow expansion of the scope of rule

15 (a) (2) beyond motions to suppress established in Anderson.

See id.     We therefore hold that the proper route for this appeal

was a petition for extraordinary relief under G. L. c. 211, § 3.

testimony by victim to police officers where victim was only
eyewitness to crime "effectively prevent[ed] the Commonwealth's
case against the defendant from proceeding").
                                                                  21

     Because this case was reserved and reported by the single

justice, we need not decide whether the case meets the standard

for relief under G. L. c. 211, § 3.    See Commonwealth v.

Whitfield, 492 Mass. 61, 67 n.9 (2023) ("Where the single

justice has exercised . . . discretion to reserve and report the

matter, we proceed to adjudicate the merits").   See also

Commonwealth v. Lucas, 472 Mass. 387, 390 (2015), quoting Burke,

373 Mass. at 159 ("where, as here, a single justice of this

court reserves and reports an interlocutory matter to this

court, we grant the litigant full appellate review").    However,

we reemphasize that G. L. c. 211, § 3, "is not a means for

second guessing a trial judge's evidentiary rulings."    Anderson,

401 Mass. at 134, quoting Yelle, 390 Mass. at 687.   Thus, even

if the Commonwealth has no other means to seek review of a trial

court's ruling on a motion in limine, that does not render

review under G. L. c. 211, § 3, automatic.    See Commonwealth v.

Fontanez, 482 Mass. 22, 25 (2019); Yelle, supra at 685-686.

Rather, to obtain review of such rulings pursuant to G. L.

c. 211, § 3, the Commonwealth "must still demonstrate to the

single justice that its petition presents the type of

exceptional matter that requires the court's extraordinary

intervention."   Fontanez, supra.

     b.   Admissibility of FLH data.   Turning to the merits of

the Commonwealth's appeal, we consider whether the trial judge
                                                                   22

abused his discretion in denying the Commonwealth's motion to

permit expert testimony on FLH data.     See Commonwealth v. Davis,

487 Mass. 448, 455 (2021), S.C., 491 Mass. 1011 (2023).     We

conclude that he did not and therefore affirm.

     Admission of scientific or technological evidence is

governed by what has come to be known as the Daubert-Lanigan

standard.16    See Daubert, 509 U.S. at 585-595; Lanigan, 419 Mass.

at 25-26.     Under the Daubert-Lanigan standard, "[t]he judge,

acting as gatekeeper, is responsible for 'mak[ing] a preliminary

assessment whether the theory or methodology underlying the

proposed testimony is sufficiently reliable to reach the trier

of fact.'"    Commonwealth v. Camblin, 478 Mass. 469, 475 (2017)

(Camblin II), quoting Commonwealth v. Shanley, 455 Mass. 752,

761 (2010).

     When considering a motion to introduce expert testimony, a

judge should initially consider five nonexclusive factors in

determining the reliability of proposed scientific evidence:

     "whether the scientific theory or process (1) has been
     generally accepted in the relevant scientific community;
     (2) has been, or can be, subjected to testing; (3) has been
     subjected to peer review and publication; (4) has an

     16Although we have adopted the Daubert-Lanigan standard,
reliability may also be established by the Frye test. See
Davis, 487 Mass. at 454 ("reliability can still be established
by general acceptance alone, without regard to the other
Daubert-Lanigan factors"); Frye v. United States, 293 F. 1013,
1014 (D.C. Cir. 1923). The Commonwealth does not rely on the
Frye test to establish reliability in this case, however.
                                                                    23

     unacceptably high known or potential rate of error; and (5)
     is governed by recognized standards."

Commonwealth v. Powell, 450 Mass. 229, 238 (2007).     If a

methodology has been determined to be reliable by our courts in

the past, a judge may take judicial notice of its reliability.

Davis, 487 Mass. at 454-455.    However, "when proposed expert

testimony uses a new theory, or new methodology to apply an

accepted theory, the proponent must establish its reliability

using a Daubert-Lanigan analysis."     Id. at 455.

     Because no court in the Commonwealth has previously deemed

FLH data to be reliable, the Commonwealth bore the burden of

establishing the reliability of FLH data under Daubert-Lanigan

by a preponderance of the evidence.     See Camblin II, 478 Mass.

at 476.17    We review a trial judge's decision on a motion in

limine to qualify or reject an expert on Daubert-Lanigan grounds

for an abuse of discretion.     Canavan's Case, 432 Mass. 304, 312

(2000).     See L.L. v. Commonwealth, 470 Mass. 169, 185 n.27

(2014) (discretionary decision constitutes abuse of discretion

where "the judge made 'a clear error in weighing' the factors

relevant to the decision, such that the decision falls outside

the range of reasonable alternatives" [citation omitted]).

     17This also appears to be an issue of first impression, as
we have not been presented with any cases from other
jurisdictions addressing the reliability of FLH data.
                                                                   24

     As an initial matter, the Commonwealth argues that the

trial judge erred in identifying the relevant field of expertise

as cellular technology, rather than digital forensics.     It

claims that this error evidences a misunderstanding of FLH data

and contributed to the trial judge's erroneous conclusion that

the analyst was not qualified to testify as an expert on FLH

data.18   Contrary to these claims, we conclude that the trial

judge correctly understood the analyst's testimony on FLH data,

and the relevant required expertise, and decided the pertinent

issue:    whether the Commonwealth had met its burden of

establishing the reliability, under the Daubert-Lanigan

standard, of FLH data.   Whether the relevant field of expertise

is characterized as cellular technology or digital forensics,

the trial judge did not abuse his discretion in determining that

the Commonwealth had not met its burden of showing that the

proffered expert testimony established the reliability of the

FLH date in this case.   See Camblin II, 478 Mass. at 476.

     i.   General acceptance.   Regarding the first Daubert-

Lanigan factor, general acceptance by the relevant scientific

community, the trial judge concluded that "[t]here [was] little

evidence that the process of obtaining and analyzing FLH data

     18Although the Commonwealth suggests that this alleged
error constitutes an error of law, it cites to no cases in
support of this claim.
                                                                   25

has been generally accepted in the scientific community."   The

primary evidence in support of general acceptance was the

analyst's conclusory testimony to that effect, which, as the

trial judge noted, was not well supported by the evidence in the

record.   The articles submitted in evidence by the Commonwealth

in support of the analyst's testimony largely discuss the

technology that produces the location data points that are used

as inputs by the FLH algorithm to output FLH data, and do not

discuss the reliability of the FLH data themselves.   The analyst

identified two digital forensics experts whose writing he

claimed supported his conclusion that FLH data have been deemed

reliable by the scientific community, but no articles by these

authors were submitted in evidence by the Commonwealth.19

Accordingly, the trial judge did not abuse his discretion in

concluding that the Commonwealth failed to meet its burden of

showing by a preponderance of the evidence that FLH data have

been generally accepted as reliable by the scientific community.

     19It is not clear why no articles by these authors were
provided as evidence of general acceptance of FLH data. We
note, however, that one of the experts named by the analyst, Ian
Whiffin, in 2021 wrote, "If I were to find encryptedB location
data in a case which was relevant to a crime scene, while I
wouldn't describe it as useless, I would be very wary of saying
it's the smoking gun." Whiffin, Harvested Locations, DoubleBlak
Digital Forensics (Mar. 26, 2021), https://www.doubleblak.com
/blogPost.php?k=Harvest [https://perma.cc/6QSM-LAAT]. According
to the analyst's testimony, Encrypted B location data are the
primary source of location data from which FLH data are
produced.
                                                                  26

See Canavan's Case, 432 Mass. at 310 (party seeking to introduce

scientific evidence bears burden of showing reliability by

establishing general acceptance or through other means).

     The Commonwealth also argues that because the FLH algorithm

uses as its inputs location data sources generally regarded as

reliable (such as GPS, CSLI, and Wi-Fi location data), the FLH

data output by the algorithm consequently is also generally

regarded as reliable.    This argument misunderstands the

Commonwealth's burden.   "[W]hen proposed expert testimony uses a

new theory, or new methodology to apply an accepted theory, the

proponent must establish its reliability using a Daubert-Lanigan

analysis."   Davis, 487 Mass. at 455.   See Commonwealth v.

Camblin, 471 Mass. 639, 650 (2015), S.C., 478 Mass. 469 (2017)

(although breathalyzer technology is generally accepted as

reliable, where new type of breath test machine had not

previously been tested and no court had considered the

reliability of its source code, "the judge should have held a

hearing to determine whether the source code and other

challenged features . . . functioned in a manner that reliably

produced accurate breath test results").   In other words, even

if the inputs used by the FLH algorithm are generally deemed

reliable, the FLH data outputs are not ipso facto reliable,

especially where there is not scientific literature or adequate

testing to support reliability.   See Davis, 487 Mass. at 457
                                                                   27

("It is not sufficient to show merely that GPS technology is, in

general, reliable without making any showing pertaining to the

reliability of a particular model of a device" using GPS

technology).

     ii.   Testing.   As to the second Daubert-Lanigan factor,

whether the technology can be or has been tested, the trial

judge did not abuse his discretion in holding that there was not

sufficient testing to establish the reliability of FLH data.

The trial judge found that the analyst's experiments with FLH

data had a small sample size.20   To test the reliability of FLH

data, the analyst jailbroke an iPhone 5C, which allowed him

access to information that is ordinarily encrypted and

inaccessible to an iPhone user.   He brought the jailbroken

iPhone to five different locations, examined the underlying

location data points gathered by the iPhone at those locations

from sources such as CSLI, Wi-Fi, and GPS, and compared these

underlying location data points to the FLH data outputs produced

on those locations.   The analyst visited each of the five

locations two or three times, for a total of twelve

     20The Commonwealth correctly points out that the judge
misstated the number of tests performed on the test iPhone. The
judge stated that there were ten experiments done by the
analyst, while the analyst testified that he performed twelve
tests of FLH data reliability at a total of five locations.
                                                                    28

experiments.21    Despite his testing, the analyst did not know the

algorithm used in creating FLH data and did not know how various

factors were weighed to create FLH data outputs.     The analyst

also could not explain how the uncertainty radius for a frequent

location was determined.    He was able to identify that the

uncertainty radius and center coordinate point for a frequent

location could change with each visit to that location, but he

was unable to explain why the uncertainty radius for a frequent

location changed or whether data from previous visits

contributed to how FLH data changed after a subsequent visit to

the location.     Moreover, while the FLH data for some locations

included a "confidence level," the analyst could not explain

what the confidence level meant, why some locations had a

confidence level and others did not, or how the confidence level

was calculated.

     The Commonwealth also argues that the trial judge abused

his discretion by failing to make findings regarding evidence

that certain frequent location visits identified on the

     21It appears from the record that the analyst performed
this testing specifically in preparation to testify in these
proceedings, which warrants closer examination of his expert
testimony and the validity of these tests. See Commonwealth v.
Rintala, 488 Mass. 421, 438 (2021), quoting Johnson v. Manitowoc
Boom Trucks, Inc., 484 F.3d 426, 434 (6th Cir. 2007) ("judges
should closely scrutinize expert testimony where the testimony
is 'prepared solely for purposes of litigation, as opposed to
testimony flowing naturally from an expert's line of scientific
research or technical work'").
                                                                     29

defendant's cell phone were corroborated by other data on the

phone.   The Commonwealth asserts that the data corroborating the

frequent location data bolsters the analyst's testing as

evidence that FLH data are reliable.   For example, the analyst

testified that frequent location no. 73 on the defendant's cell

phone corresponded to a location at a mall in Newton.     The FLH

data suggested that the cell phone was at frequent location no.

73 from 7:26 P.M. to 7:32 P.M. on March 29, 2015, two days

before the murder.   The uncertainty radius for frequent location

no. 73 was ninety-one meters, meaning the FLH data represented

that the cell phone was likely within a ninety-one meter radius

of the determined center point for location no. 73.     Two images

recovered from the defendant's cell phone were taken at 7:31

P.M. and 7:32 P.M. on March 29, and appear to have been taken in

the northwest corner of the mall parking garage.   The

Commonwealth suggests that the pictures corroborate the

reliability of frequent location no. 73 because they place the

defendant near the location during the relevant time.     The

analyst testified regarding four other frequent locations

extracted from the defendant's cell phone that were corroborated

either by pictures taken on the phone indicating it was in the

area of the frequent location during the relevant time period,

or by data showing the phone connected to Wi-Fi networks
                                                                   30

associated with a location while the FLH data indicated the

phone was at the location.22

     Although the trial judge did not make any findings

regarding the corroborated frequent location evidence presented

by the Commonwealth, judges are not required to make explicit

findings on all the evidence presented at a hearing.   See

Commonwealth v. Tremblay, 480 Mass. 645, 660 (2018) (although

judges have obligation to make adequate findings, "motion judges

need not making findings with respect to every piece of evidence

in the record, irrespective of pertinence").   Although it would

have been preferable for the judge to make explicit findings

regarding the corroborated frequent locations, it was not error

     22The evidence did not always unambiguously indicate the
reliability of the FLH data. On cross-examination, the analyst
admitted that the pictures taken in the mall parking garage
appear to have been taken 272 feet outside the uncertainty
radius for frequent location no. 73. The analyst later
explained that because frequent location no. 73 had been visited
fourteen times, the center point and uncertainty radius for the
location could have shifted over time.

     The analyst also provided testimony regarding frequent
location no. 122, which roughly corresponded to the location of
an apartment complex in Randolph. The analyst testified that
the FLH data for frequent location no. 122 showed that the
defendant's cell phone entered the frequent location at 10:55
P.M. on March 25, 2015, and left the location at 6:45 A.M. the
next morning. The defendant's cell phone connected to Wi-Fi
networks also associated with the Randolph apartment complex at
11:17 P.M. on March 25, 2015, as well as 6:45 A.M. on March 26.
The FLH data would thus suggest that the cell phone left the
apartment complex the same minute that it connected to a Wi-Fi
network at the complex on the morning of March 26.
                                                                  31

for him to omit them from his ruling.23   Even if evidence of the

five corroborated locations are considered alongside the twelve

experiments conducted by the analyst, it was well within the

trial judge's discretion to hold that the Commonwealth had not

met its burden of showing that FLH data had been sufficiently

tested to show its reliability.    See Commonwealth v. Rintala,

488 Mass. 421, 440-441 (2021) (testing was insufficient and

expert opinion was therefore unreliable where six experiments

were not repeated or validated).   See also National Research

Council, Strengthening Forensic Science in the United States:     A

Path Forward 112 (2009) ("Typically, experiments or observations

must be conducted over a broad range of conditions before the

roles of specific factors, patterns, or variables can be

understood").24

     23We also note that the trial judge had only four days to
decide the motion to admit FLH data, in part because it appears
the Commonwealth was unprepared in July 2023 when the hearing
was originally scheduled to take place. The time pressure may
have contributed to the judge's decision not to widen his scope
of analysis to include explicit findings on the corroborating
FLH data evidence.

     24State v. Pierce, 222 A.3d 582 (Del. Super. Ct. 2019),
aff'd, 236 A.3d 307 (Del. 2020), provides an apt comparison. In
Pierce, prosecutors sought to admit "Google Wi-Fi location data"
sent between a cell phone running the Android operating system
and Google. Id. at 583. To support the reliability of the Wi-
Fi location data, an engineer with twenty years of experience
working at Oracle, a major software firm, testified. Id. at
588. The engineer constructed a "test rig" device containing
twenty cell phones "which operate[d] as a 'man-in-the-middle'
exploit to observe the signals sent by the devices to Google."
                                                                    32

     iii.   Other Daubert-Lanigan factors.   Finally, we consider

whether the trial judge abused his discretion in his discussion

of the other Daubert-Lanigan factors:   whether FLH data evidence

"(3) has been subjected to peer review and publication; (4) has

an unacceptably high known or potential rate of error; and (5)

is governed by recognized standards."   Davis, 487 Mass. at 454,

quoting Powell, 450 Mass. at 238.   It is undisputed that the

testing of FLH data performed by the analyst was neither peer-

reviewed nor published.   In terms of other publications, the

trial judge found that the articles and materials submitted by

Id. at 589. The engineer used the test rig for a period of two
years and analyzed communications between the cell phones in the
test rig and Google to determine the accuracy of Wi-Fi location
data in a variety of locations. Id. Additionally, the engineer
deployed the test rig near the scene of the crime and determined
that the density of Wi-Fi signals in the area was sufficient to
reliably identify the location of the defendant's cell phone
within approximately one hundred feet. Id. The extensive
testing done by an experienced engineer at a major software firm
over the course of two years is very different from the twelve
tests conducted by the analyst, even if the corroborating FLH
data are considered. To be clear, we do not suggest that the
exact credentials or testing procedures used in Pierce are what
would be required to show that FLH data are reliable. However,
the comparison to Pierce illustrates that the trial judge did
not abuse his discretion in holding that the limited testing
done by the analyst in this case was insufficient to establish
FLH data reliability. We further note that the Commonwealth
argued that the Google Wi-Fi location data found reliable in
Pierce and the FLH data at issue here are analogous, and thus
FLH data should be considered reliable. We certainly cannot, on
this record, conclude that Wi-Fi location data on the Android
cell phone operating system are so similar to FLH data that
Pierce somehow establishes the reliability of the FLH data at
issue here.
                                                                  33

the Commonwealth discussing the underlying technology (GPS, Wi-

Fi, and CSLI) were not "particularly instructive."    He also

noted that there were "very few references to FLH in any of the

papers submitted into evidence."   After a review of the articles

referenced, we agree.   The analyst referenced other experts in

the field of digital forensics who informed his opinion that FLH

data are generally regarded as reliable, but no articles written

by those experts, peer-reviewed or not, appear in the record

produced by the Commonwealth.   Therefore, the trial judge did

not abuse his discretion in holding that the Commonwealth had

failed to show evidence that FLH data have been subjected to

peer review or publication.

     The trial judge held that the fifth prong of Daubert-

Lanigan, recognized standards, was satisfied by the existence

and admission in evidence of Federal regulations setting

standards for analyzing cell phone location information

generally.   See Matter of E911 Location Accuracy Requirements,

Fourth Report and Order, 30 F.C.C.R. 1259 (2015).25   The

Commonwealth argues on appeal that because Federal regulations

exist for cell phone location information and were in effect at

the time of the murder, the fourth prong, known or potential

     25We note that such regulations do not address FLH data
specifically. We need not, however, resolve whether the fifth
prong was factored properly to conclude that the reliability of
FLH data was not established.
                                                                    34

rate of error, must also logically be met.    The Commonwealth

does not otherwise provide any evidence or argument as to why

the trial judge erred in holding that it had failed to meet its

burden on the fourth prong.    In any event, we see no abuse of

discretion by the trial judge in holding that the fourth prong

was not met, particularly because of the various characteristics

of FLH data that the analyst could not explain, including the

uncertainty radius and confidence level.

     For the reasons discussed, the trial judge did not abuse

his discretion in holding the Commonwealth failed to establish

the reliability of FLH data.   See Davis, 487 Mass. at 455.      The

judge thus correctly denied the motion to permit the proffered

expert testimony on FLH data evidence at trial.

     3.   Conclusion.   Because the challenged evidentiary ruling

involved neither the determination of a motion to suppress nor

the pretrial exclusion pursuant to a motion in limine of

evidence that, as a practical matter, would terminate the

Commonwealth's prosecution of the defendant, the Commonwealth's

avenue for interlocutory review of the ruling was a petition for

extraordinary relief under G. L. c. 211, § 3, rather than an

interlocutory appeal under rule 15 (a) (2).    Moreover, having

considered the merits of the Commonwealth's petition, we

conclude that the trial judge did not abuse his discretion in

denying the Commonwealth's motion in limine to admit the
                                                                  35

proffered expert testimony regarding the FLH data.   Accordingly,

we remand the case to the county court for entry of a judgment

affirming the trial court judge's order and remanding the matter

to the trial court for further proceedings consistent with this

opinion.

                                   So ordered.
     LOWY, J. (concurring, with whom Georges, J., joins).     I

agree with the court that Mass. R. Crim. P. 15 (a) (2), as

appearing in 474 Mass. 1501 (2016), was not the proper avenue

for interlocutory review of the trial judge's ruling, and that

the trial judge did not abuse his discretion in denying the

Commonwealth's motion in limine to admit its proffered expert

testimony on the frequent location history (FLH) data retrieved

from the defendant's cell phone.   I write separately to

highlight that, although the trial judge did not abuse his

discretion in this case in ruling that the Commonwealth failed

to satisfy the Daubert-Lanigan standard, see Daubert v. Merrell

Dow Pharms., Inc., 509 U.S. 579, 585-595 (1993); Commonwealth v.

Lanigan, 419 Mass. 15, 25-26 (1994), a party may well meet its

burden to show gatekeeper reliability of expert testimony

regarding FLH data in another pending or future case, see Mass.

G. Evid. §§ 104(a), 702 (2023).

     Indeed, FLH data -- like all technology -- is an area

"where knowledge is evolving, and new understandings may be

expected as more studies and tests are conducted."   Commonwealth

v. Shanley, 455 Mass. 752, 763 n.15 (2010).   The Commonwealth

failed to demonstrate here that FLH data can reliably establish

that an iPhone was in an approximate area at an estimated time

for several reasons, including the lack of evidence that FLH

data has been generally accepted in the scientific community,
                                                                     2

the absence of articles and peer-reviewed studies offered in

evidence supporting the reliability of FLH data, the lack of

information as to whether there is an unacceptably high known or

potential rate of error for FLH data, the expert's lack of

knowledge about the algorithm used to create FLH data, and the

inadequacy of the expert's testing, which had a small sample

size, was completed over a short time frame and for the purpose

of this case, and was neither peer-reviewed nor published.      As

more becomes known about FLH data, a party attempting to prove

gatekeeper reliability may cure many, if not all, of the

Commonwealth's deficiencies.   In other words, it is possible

that a party may not need an expert from Apple to testify about

the proprietary algorithm creating FLH data to establish

gatekeeper reliability.   In sum, I write separately to emphasize

that today's ruling does not dictate the result at a Daubert-

Lanigan hearing in another case based upon either existing or

evolving technology.    Cf. Commonwealth v. Davis, 487 Mass. 448,

457-458 (2021), S.C., 491 Mass. 1011 (2023) (Commonwealth failed

to show that global positioning system evidence could reliably

demonstrate speed that defendant was moving during crime and

judge abused his discretion in admitting such evidence, but

Commonwealth could attempt to lay proper foundation for speed

evidence on retrial).