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             DISTRICT OF COLUMBIA COURT OF APPEALS

                                No. 16-CO-523

                           UNITED STATES, APPELLANT,

                                       V.

                         ZACKARY JACKSON, APPELLEE.

                         Appeal from the Superior Court
                          of the District of Columbia
                                 (CF3-2512-15)

                     (Hon. Maribeth Raffinan, Trial Judge)

(Argued October 26, 2016                             Decided August 22, 2019)

      Nicholas P. Coleman, Assistant United States Attorney, with whom
Channing D. Phillips, United States Attorney at the time the brief was filed, and
Elizabeth Trosman, Chrisellen R. Kolb, Alicia M. Long, and Anwar Graves,
Assistant United States Attorneys, were on the brief, for appellant.

     Daniel Gonen, Public Defender Service, with whom Samia Fam and Jaclyn
Frankfurt, Public Defender Service, were on the brief, for appellee.


     Before BLACKBURNE-RIGSBY, * Chief Judge, GLICKMAN, Associate Judge,
and WASHINGTON, † Senior Judge.

      *
         Chief Judge Blackburne-Rigsby was an Associate Judge at the time oral
argument was held on October 26, 2016. Judge Blackburne-Rigsby assumed the
duties of Chief Judge on March 18, 2017.
                                        2

      GLICKMAN, Associate Judge: The United States appeals a pretrial order

suppressing appellee Zackary Jackson’s Global Positioning System (GPS) tracking

data and derivative evidence in its prosecution of Mr. Jackson for armed robbery.

The tracking data was collected and maintained by the District of Columbia Court

Services and Offender Supervision Agency (CSOSA) after it required Mr. Jackson

to wear a GPS tracking device on his ankle as a sanction for his having violated

conditions of his probation in an earlier case. CSOSA gave the police access to the

GPS data, and the data revealed to the police that Mr. Jackson was present at the

scene of the armed robbery with which he is now charged. The police used the

data to track Mr. Jackson from the location of the robbery to his home, where they

arrested him and found tangible evidence linking him to the crime.




      In moving to suppress the GPS data and its fruits, Mr. Jackson argued that

CSOSA violated his Fourth Amendment rights by placing him on GPS monitoring

for purposes of law enforcement without judicial authorization and that the police

violated his Fourth Amendment rights by accessing the GPS tracking data without



(…continued)
      †
         Senior Judge Pryor, who was assigned to this case originally and at the
time of oral argument, retired on May 15, 2019. Senior Judge Washington was
assigned to take his place on the division.
                                        3

a search warrant. Addressing only the latter issue, the motions judge concluded

that the police search infringed Mr. Jackson’s reasonable expectation of privacy in

his GPS data and, therefore, violated his Fourth Amendment rights.



      We reverse. First, as a threshold matter, we hold that CSOSA’s imposition

of GPS monitoring on Mr. Jackson without judicial authorization was a

constitutional “special needs” search; it was constitutional because his reasonable

expectation of privacy as a convicted offender on probation was diminished and

was outweighed by the strong governmental interests in effective probation

supervision to deter and detect further criminal activity on his part and encourage

his rehabilitation. We reject, as unsupported by the record, Mr. Jackson’s claim

that CSOSA placed him on GPS monitoring as a subterfuge to enable the police to

avoid having to comply with the warrant and probable cause requirements of the

Fourth Amendment. Second, we conclude that Mr. Jackson had no objectively

reasonable expectation that CSOSA would withhold the GPS tracking data from

the police. The limited police examination of that data—which focused solely on

determining whether any monitored CSOSA supervisee was present during the

armed robbery (and if so, where that supervisee went immediately afterwards)—

therefore did not violate Mr. Jackson’s Fourth Amendment rights.
                                          4

                                          I.



                A. Mr. Jackson’s Placement on GPS Monitoring



      On December 13, 2013, Mr. Jackson pleaded guilty in Superior Court to one

count of attempted robbery. Mr. Jackson had been charged with armed robbery.

In tendering his guilty plea to the lesser offense, he admitted that he and two

accomplices put on masks inside the Benning Road Metro station and robbed the

victim of his cell phone by threatening him with a BB pistol.



      Three months later, the judge sentenced Mr. Jackson to twelve months’

incarceration, with all but four months suspended in favor of one year of probation

under the supervision of CSOSA. The court-imposed conditions of his probation

included requirements that Mr. Jackson (1) “[o]bey all laws, ordinances, and

regulations”; (2) permit his Community Supervision Officer [CSO] to visit his

place of residence; (3) report to all scheduled appointments with his CSO; (4)

notify his CSO within one business day of any arrest or questioning by a law

enforcement officer; (5) submit to drug testing at the discretion of CSOSA; (6)

participate in and complete CSOSA programs as directed; and (7) “[i]n the event of

illicit drug use or other violation of conditions of probation, participate as directed
                                        5

by [his] CSO in a program of graduated sanctions that may include periods of

residential placement or services.”



      Mr. Jackson’s period of probation began in July 2014. It did not go well.

Mr. Jackson failed to report for scheduled appointments with his CSO on five

occasions, in August, December, and January; he did not pursue gainful

employment as required by CSOSA programming; and on December 23, 2014, Mr.

Jackson was re-arrested in Virginia.1



      Thereafter, in January 2015, a detective with the Metropolitan Police

Department (MPD) contacted CSOSA to request that Mr. Jackson be placed on

GPS monitoring, one of the options in CSOSA’s program of graduated sanctions

for non-compliant behavior. As stated in CSOSA’s internal emails, the detective

made this request because the police believed Mr. Jackson and another named

individual “may” have been committing robberies and burglaries together at a



      1
         According to CSOSA’s running record of Mr. Jackson’s supervision, he
was released following his new arrest and was due back in court the following
month. In the hearing below on the evidence suppression motion, counsel for the
United States represented that Mr. Jackson was arrested in Virginia for “a felony
pickpocket.” The record on appeal does not appear to provide any additional
information about the nature of the charge in Virginia or the outcome of the
proceedings there.
                                         6

particular Metro station in the District and elsewhere. The police request triggered

a review by CSOSA of Mr. Jackson’s compliance with his terms of probation to

determine whether he met the agency’s criteria for GPS monitoring. Citing Mr.

Jackson’s re-arrest, lack of employment, and failure to look for work and

participate in CSOSA programming, the agency decided he should be placed on

GPS monitoring “immediately.” 2



      Mr. Jackson’s CSO met with him on January 28, 2015. She questioned him

about his missed appointments and his involvement in criminal activity (which he

denied), and she informed him that he would be placed on GPS monitoring.

According to her record of the meeting, Mr. Jackson was “visibly upset” by that

decision and “stated he wouldn’t be able to do anything.” The CSO emphasized




      2
         CSOSA’s published Policy Statement 4008, “Global Positioning System
(GPS) Tracking of Offenders,” effective May 7, 2009, https://www.csosa.gov/wp-
content/uploads/bsk-pdf-manager/2018/03/4008_gps_tracking_050709.pdf          (last
visited June 13, 2019), sets forth the procedures CSOSA follows in connection
with the imposition of GPS tracking of offenders. The Policy Statement provides
that an offender under supervision may be referred for placement on GPS as a
sanction if, among other things, the offender is re-arrested and released into the
community pending further judicial action, or if the offender is unemployed, at a
maximum or intensive level of supervision, and not actively searching for
employment or in school or a training program.
                                         7

that although Mr. Jackson would not have a curfew, “he must be aware that

[CSOSA] will be tracking his whereabouts for at least 30 days.”3



       The next day, Mr. Jackson reported to CSOSA for the GPS device – a small

bracelet transmitter with a strap – to be fitted and attached to his ankle. He signed

a “CSOSA Global Positioning System (GPS) Contract,” in which he acknowledged

his understanding that “all GPS activities will be monitored by CSOSA’s (24/7)

Monitoring Center,” and that “all movement will be tracked and stored as an

official record.” The contract required Mr. Jackson to wear the GPS device at all

times and not to tamper with it for any reason. It also required him to charge the

device twice a day, an hour in the morning and an hour in the evening, and not to

sleep while the device was charging. The contract stated that the device was

waterproof and did not prevent him from taking showers, but that he should not

submerge the device in water (meaning he could not bathe or swim while wearing

it).




       3
         CSOSA’s Policy Statement on GPS tracking of supervised offenders,
supra, footnote 2, provides that when GPS tracking is employed as a sanction for
non-compliant behavior, it may be implemented for up to thirty days and, when
aggravating circumstances exist, extended for up to a total of ninety days.
                                       8

                 B. An Armed Robbery and Its Investigation



      Early on the morning of February 19, 2015 (less than three weeks after Mr.

Jackson began wearing the GPS device), police received a report of an armed

robbery in the 4400 block of C Street in Southeast Washington, D.C. As the

victims, Mr. Parker and Ms. Pleasant, described the incident, they were walking

home together and, after turning from Texas Avenue onto C Street, they passed by

an alley on their left. In the alley, they noticed a newer model black SUV that

pulled out and drove toward the intersection of Texas Avenue and C Street. Mr.

Parker looked back and saw the SUV pause at the traffic light there. Ms. Pleasant

asked him what time it was, and Mr. Parker checked his cell phone and told her it

was 1:36 a.m.



      As he put the cell phone back in his pocket, Mr. Parker looked back again

and saw the SUV speeding toward him and Ms. Pleasant in reverse. The SUV

stopped right in front of them. Two men got out of the back seats. One displayed

a small, black handgun and took Mr. Parker’s wallet. The other man took Ms.

Pleasant’s purse. The two men then returned to the SUV, which drove off toward

Texas Avenue. The two victims got home and called the police.
                                           9

      Detective Thomas O’Donnell of the MPD interviewed the complainants

shortly after they reported the robbery. Although they provided detailed physical

descriptions of their assailants, the robbers’ identities were unknown and there

were no suspects or other witnesses. Detective O’Donnell decided to run a check

to determine whether any supervisees under GPS monitoring by CSOSA were at

the crime scene at the time of the offense. He had access to the computerized GPS

tracking data pursuant to a Memorandum of Understanding in which CSOSA

agreed to share it with the MPD and allowed the police to query the database

directly. 4 The monitoring system tracks and records the movements of the GPS

devices in one-minute increments, twenty-four hours a day, seven days a week.

Detective O’Donnell entered the coordinates of the crime scene into the database

to determine whether any monitored supervisees were in the area between 1:20

a.m. to 1:45 a.m.



      His GPS check produced two hits. It revealed that Mr. Jackson and another

CSOSA supervisee were in the alley where the victims saw the SUV just before

the robbery occurred. From the alley, their movements conformed to the victims’

observations of their attackers: the GPS data showed that Mr. Jackson and the


      4
          We describe this sharing arrangement further in Part II.B of this opinion.
                                         10

second person moved toward the intersection of Texas Avenue and C Street, then

went back into the 4400 block of C Street, and then went back to Texas Avenue.

The GPS data also allowed the police to track the two suspects’ subsequent

movements as they briefly separated and then reunited in the rear parking lot of

4410 E Street, Southeast. The data showed that Mr. Jackson then went into an

apartment at 4410 E Street and that the other suspect went to a location a block

away.



        The police immediately went to the two destinations. They arrived at Mr.

Jackson’s apartment building between 2:00 and 3:00 a.m. Mr. Jackson’s GPS

device continued to show him as being there. In the rear parking lot, the officers

saw a black, newer model SUV.           Mr. Parker, who accompanied Detective

O’Donnell, identified the SUV as the one the robbers used. 5 On the ground near

the stairs leading to the building entrance, the police found a bank card in Mr.

Parker’s name.



        The police proceeded to Mr. Jackson’s apartment to arrest him and secure

the location while they applied for a warrant to search it. In the apartment, they



        5
            WALES and NCIC checks indicated that the SUV had been stolen.
                                         11

found Mr. Jackson with three other people. After obtaining the search warrant, the

police recovered the keys to the SUV and some items that may have been in Ms.

Pleasant’s purse.6



      Mr. Jackson was arrested. He subsequently was charged by indictment with

two counts of armed robbery, first-degree theft (of the SUV), and unauthorized use

of a vehicle (the SUV) to facilitate a crime of violence.



               C. The Trial Court’s Suppression of the Evidence



      Following his arraignment, Mr. Jackson moved to suppress the electronic

and tangible evidence linking him to the robberies. Among his claims, he argued

that his Fourth Amendment rights were violated by CSOSA’s imposition of GPS

monitoring at the behest of the police and by the subsequent warrantless police

search of the GPS tracking data. After a hearing, and on largely undisputed facts,

the motions judge granted the motion to suppress on the latter ground, that the

police search of the GPS data was unconstitutional. The judge did not address the

constitutionality of CSOSA’s GPS monitoring of Mr. Jackson.

      6
         The police also searched the second suspect’s residence. They reportedly
found him in a downstairs bedroom, lying on top of a cell phone that matched the
description of the phone in Ms. Pleasant’s stolen purse.
                                       12

      The judge based her ruling on her conclusion that Mr. Jackson reasonably

expected that the police would not have access to his GPS tracking data. In

reaching that conclusion, the judge acknowledged that Mr. Jackson was on

probation and that, “[g]iven the language of the GPS Contract, it would be

unreasonable for Jackson to expect privacy in his GPS location information as to

CSOSA.” (Emphasis added.) However, the judge noted, the conditions of Mr.

Jackson’s probation and his GPS Contract did not inform him, “clear[ly] and

unambiguous[ly],” that the location data would be shared with or accessible to the

police. Absent such notification, the judge stated, Mr. Jackson “could not have

reasonably foreseen that the MPD would have unfettered, unilateral access to his

location information for developing suspects and finding witnesses in criminal

cases.” Because the police lacked “any level of individualized suspicion” linking

Mr. Jackson to the robberies before they queried the GPS database, the judge

concluded that Mr. Jackson’s undiminished expectation of privacy vis-à-vis the

police outweighed “the MPD’s general interest in criminal investigation.”

Accordingly, the judge held, the police search of Mr. Jackson’s GPS location data

was “unreasonable under the Fourth Amendment.”
                                            13

                                            II.



      Two distinct Fourth Amendment issues are presented in this appeal. Given

the undisputed factual record before us, each turns on legal questions that we

decide de novo.     The first is whether CSOSA violated Mr. Jackson’s Fourth

Amendment rights by placing him on GPS monitoring without judicial approval.

This issue turns, as we shall explain, on whether the monitoring was justified as a

reasonable intrusion on Mr. Jackson’s privacy to meet the “special needs” of

probation supervision. We address this legal issue, even though the motions judge

granted suppression for other reasons, because it was litigated in the proceedings

below, Mr. Jackson continues to urge it on appeal as an alternative ground for

affirmance, and the United States has had a full and fair opportunity to rebut the

claim. 7 Moreover, our resolution of the second Fourth Amendment issue before us

depends on our answer to the first issue.



      The second issue is whether the police conducted an unconstitutional search

when, without having a search warrant or individualized suspicion, they queried

CSOSA’s GPS database and acquired the information it contained about Mr.



      7
          See Ibn-Tamas v. United States, 407 A.2d 626, 635-36 (D.C. 1979).
                                        14

Jackson’s location and movements at the time and in the immediate vicinity of the

robbery. Assuming the lawfulness of CSOSA’s acquisition of that information in

the first place, this issue turns in our view on whether CSOSA violated Mr.

Jackson’s reasonable expectation of privacy by allowing the police to access its

GPS database for the limited use the police made of it.



      We address these two issues in turn.8




      8
           In the proceedings below, the United States argued that CSOSA’s
imposition of GPS monitoring did not violate Mr. Jackson’s Fourth Amendment
rights because he consented to it when he agreed to the GPS contract. See
generally Schneckloth v. Bustamonte, 412 U.S. 218 (1973). Mr. Jackson disputed
that claim, arguing that his mere acquiescence to the monitoring did not amount to
a valid waiver of his Fourth Amendment rights. The motions judge did not address
this issue of consent in her decision, and while the United States does not concede
the issue, it has not pressed the consent argument on appeal. We do not find it
necessary to reach the question; to quote the Second Circuit’s observation in a
similar case, “[t]he issue here … is not so much whether [Mr. Jackson] gave
consent as it is whether he had a reasonable and legitimate expectation of privacy.”
United States v. Lambus, 897 F.3d 368, 410 (2d Cir. 2018); see also United States
v. Knights, 534 U.S. 112, 118 (2001) (refraining from deciding whether
probationer’s acceptance of a search condition “constituted consent in the
Schneckloth sense of a complete waiver of his Fourth Amendment rights,” because
the Court could conclude that the search “was reasonable under our general Fourth
Amendment approach of ‘examining the totality of the circumstances,’ . . . with the
probation search condition being a salient circumstance” (internal citation
omitted)).
                                         15

      A. CSOSA Did Not Violate Mr. Jackson’s Fourth Amendment Rights
by Placing Him on GPS Monitoring and Tracking His Movements.


             1. The Special Needs of Probation Supervision Recognized in
Griffin v. Wisconsin


      It is common ground that when the government “attaches a device to a

person’s body, without consent, for the purpose of tracking that individual’s

movements,” it conducts a search subject to the Constitution’s requirements. 9 The

government’s use of the device to monitor the person’s movements also constitutes

a search for Fourth Amendment purposes. 10



      The Fourth Amendment to the Constitution protects the right of the people

to be secure against searches and seizures that are “unreasonable.”11 Thus, as

“[t]he touchstone of the Fourth Amendment is reasonableness,” 12 the central

question before us is the reasonableness vel non of CSOSA’s GPS monitoring of

Mr. Jackson.       Resolution of this question “depends on the totality of the

circumstances, including the nature and purpose of the search and the extent to

      9
           Grady v. North Carolina, 135 S.Ct. 1368, 1370 (2015).
      10
           See United States v. Jones, 565 U.S. 400, 404 (2012).
      11
           U.S. Const. amend. IV.
      12
           Knights, 534 U.S. at 118.
                                         16

which the search intrudes upon reasonable privacy expectations.” 13 We determine

whether a search is reasonable “by assessing, on the one hand, the degree to which

it intrudes upon an individual’s [reasonable expectation of] privacy and, on the

other, the degree to which it is needed for the promotion of legitimate

governmental interests.”14     The Supreme Court has characterized this as a

balancing test.15



      “Where a search is undertaken by law enforcement officials to discover

evidence of criminal wrongdoing, . . . reasonableness generally requires the

obtaining of a judicial warrant” upon the showing of probable cause required by

the Fourth Amendment’s Warrant Clause.16 But the Court has explained that:




      13
           Grady, 135 S.Ct. at 1371.
      14
          Knights, 534 U.S. at 118-19 (quoting Wyoming v. Houghton, 526 U.S.
295, 300 (1999)).
      15
          See, e.g., Vernonia Sch. Dist. 47J v. Acton, 515 U.S. 646, 652-53 (1995)
(“At least in a case such as this, where there was no clear practice, either approving
or disapproving the type of search at issue, at the time the constitutional provision
was enacted, whether a particular search meets the reasonableness standard ‘“is
judged by balancing its intrusion on the individual’s Fourth Amendment interests
against its promotion of legitimate governmental interests.’” (quoting Skinner v.
Ry. Labor Execs.’ Ass’n, 489 U.S. 602, 619 (1989))).
      16
           Acton, 515 U.S. at 653.
                                          17

              [A] warrant is not required to establish the
              reasonableness of all government searches; and when a
              warrant is not required (and the Warrant Clause therefore
              not applicable), probable cause is not invariably required
              either. A search unsupported by probable cause can be
              constitutional . . . “when special needs, beyond the
              normal need for law enforcement, make the warrant and
              probable-cause requirement impracticable.”[17]


Nor do searches motivated by “special needs, beyond the normal need for law

enforcement” necessarily require a degree of “individualized suspicion of

wrongdoing” in the absence of probable cause; “the Fourth Amendment imposes

no irreducible requirement of such suspicion.” 18



      In Griffin v. Wisconsin, the Supreme Court considered whether the operation

of a probation system presents “special needs” beyond the normal need for law

enforcement that may justify exempting supervisory searches of probationers from


      17
           Id. (quoting Griffin v. Wisconsin, 483 U.S. 868, 873 (1987)).
      18
           Id. (quoting United States v. Martinez-Fuerte, 428 U.S. 543, 560-61
(1976)). The Court has upheld suspicionless searches and seizures under “special
needs” or similar rationales in a variety of situations – for instance, in Acton, 515
U.S. at 653-65 (upholding random urinalysis drug testing of students in school
athletics programs; Skinner, 489 U.S. at 633-34 (drug testing of railroad personnel
involved in train accidents); Nat’l Treasury Emps. Union v. Von Raab, 489 U.S.
656, 666, 676 (1989) (drug tests for U.S. Customs Service employees seeking
transfers or promotions); New York v. Burger, 482 U.S. 691, 702-04 (1987)
(warrantless administrative inspections of the premises of “closely regulated”
businesses).
                                             18

the requirements the Fourth Amendment imposes on “normal” law enforcement

searches. The question arises, even though both types of searches aim to discover

evidence of criminal activity, because supervisory searches of probationers are

unlike “normal” law enforcement searches in that they are conducted as part of the

distinctive probation mission to reform convicted offenders and deter them from

committing new crimes. The Court was persuaded in Griffin of the significance of

this contextual difference, and it applied the “special needs” rationale to uphold a

warrantless search of a probationer’s home under circumstances parallel, in

important respects, to those in this case.



      The facts of Griffin were as follows. Under Wisconsin law, probationers

were subject to the conditions of probation set by the court at sentencing and to the

regulations of the probation department.          One such regulation allowed any

probation officer to search any probationer’s home, without a warrant or other

prior judicial approval, so long as there were “reasonable grounds” to believe
                                         19

contraband was present in the home. 19 This home-search authorization was not

one of the court-imposed conditions of Griffin’s probation. 20



      While Griffin was on probation, the probation office received information

from a police detective that “there were or might be guns” in Griffin’s apartment.21

Two probation officers, accompanied by three police officers, went there to find

out. Relying on the home-search regulation, they did not apply for a search

warrant. When Griffin opened the door, one of the probation officers “informed

him that they were going to search his home.” 22 They found and seized a handgun.

Griffin was prosecuted for felony possession of a firearm. He moved to suppress

the handgun, arguing that the probation officers’ search of his home without a
      19
           Griffin, 483 U.S. at 871; see also Knights, 534 U.S. at 117 (“The
regulation applied to all Wisconsin probationers, with no need for a judge to make
an individualized determination that the probationer’s conviction justified the need
for warrantless searches.”).
      20
          In fact, the regulation was not promulgated until a year after Griffin was
sentenced and placed on probation. See Knights, 534 U.S. at 117 & 117 n.2 (citing
Griffin, 483 U.S. at 870, 871).
      21
          Griffin, 483 U.S. at 871. The Court considered it “most unlikely” that
this “unauthenticated tip of a police officer – bearing, as far as the record shows,
no indication whether its basis was firsthand knowledge or, if not, whether the
firsthand source was reliable, and merely stating that Griffin ‘had or might have’
guns in his residence, not that he certainly had them – would meet the ordinary
requirement of probable cause.” Id. at 878.
      22
           Id.
                                                20

warrant violated the Fourth Amendment. The court denied the motion and Griffin

was convicted.



      The Supreme Court held that “[t]he search of Griffin’s home satisfied the

demands of the Fourth Amendment because it was carried out pursuant to a

regulation    that   itself   satisfies   the    Fourth   Amendment’s   reasonableness

requirement” under the “well-established” exception to the warrant requirement for

“special needs” searches.23 The Court explained its holding as follows. First, it

perceived it to be “always true of probationers . . . that they do not enjoy ‘the

absolute liberty to which every citizen is entitled, but only . . . conditional liberty

properly dependent on observance of special [probation] restrictions’” –

restrictions “meant to assure that the probation serves as a period of genuine

rehabilitation and that the community is not harmed by the probationer’s being at

large.”24 “These same goals,” the Court stated, “require and justify the exercise of

supervision to assure that the restrictions are in fact observed.” 25 Moreover, the

Court noted, “[r]ecent research suggests that more intensive supervision can reduce



      23
           Id. at 873.
      24
           Id. at 874-75 (quoting Morrissey v. Brewer, 408 U.S. 471, 480 (1972)).
      25
           Id. at 875.
                                            21

recidivism, . . . and the importance of supervision has grown as probation has

become an increasingly common sentence for those convicted of serious crimes.”26

In light of these considerations, the Court concluded that probation supervision “is

a ‘special need’ of the State permitting a degree of impingement upon privacy that

would not be constitutional if applied to the public at large.” 27



      Second, the Court found multiple reasons to conclude that the special needs

of probation supervision make the usual warrant and probable-cause requirements

of the Fourth Amendment impracticable. It stated:


                 A warrant requirement would interfere to an appreciable
                 degree with the probation system, setting up a magistrate
                 rather than the probation officer as the judge of how
                 close a supervision the probationer requires. Moreover,
                 the delay inherent in obtaining a warrant would make it
                 more difficult for probation officials to respond quickly
                 to evidence of misconduct, and would reduce the
                 deterrent effect that the possibility of expeditious
                 searches would otherwise create. . . . And on the other
                 side of the equation—the effect of dispensing with a
                 warrant upon the probationer: Although a probation
                 officer is not an impartial magistrate, neither is he the
                 police officer who normally conducts searches against

      26
           Id.
      27
          Id.; see also Ferguson v. City of Charleston, 532 U.S. 67, 79 n.15 (2001)
(“Griffin is properly read as limited by the fact that probationers have a lesser
expectation of privacy than the public at large.”).
                                           22

              the ordinary citizen. He is an employee of the [state
              probation department] who, while assuredly charged with
              protecting the public interest, is also supposed to have in
              mind the welfare of the probationer . . . . In such a
              setting, we think it reasonable to dispense with the
              warrant requirement.[28]


The Court also concluded that probation supervision would be “unduly disrupted”

by a requirement that there be probable cause to search the probationer’s home,

among other reasons because (1) such a requirement “would reduce the deterrent

effect of the supervisory arrangement;” (2) “the probation agency must be able to

act based upon a lesser degree of certainty than the Fourth Amendment would

otherwise require in order to intervene before a probationer does damage to

himself or society;” and (3) “it is the very assumption of the institution of

probation that the probationer is in need of rehabilitation and is more likely than

the ordinary citizen to violate the law.” 29



      In sum, under the “special needs” analysis of Griffin, the Fourth Amendment

permits probation supervision to intrude significantly on probationers’ privacy

without judicial approval or probable cause in order to determine whether they are


      28
           Griffin, 483 U.S. at 876-77.
      29
         Id. at 878-80; see also Knights, 534 U.S. at 120 (“The recidivism rate of
probationers is significantly higher than the general crime rate.”).
                                        23

abiding by the law and the conditions of their probation, because probationers’

reasonable privacy expectations are diminished and are outweighed by the

heightened governmental interests in deterring them from re-offending and

promoting their rehabilitation.30



           2. CSOSA’s Special Need to Use GPS Monitoring as an
Administrative Sanction for High-Risk Supervisees


      Griffin’s “special needs” analysis applies to CSOSA’s installation of a GPS

device on Mr. Jackson’s ankle to monitor his movements.          CSOSA is the

counterpart in the District to the state probation department in Griffin. It is a

federal agency charged by law with providing “supervision, through qualified

supervision officers, for offenders on probation, parole, and supervised release

pursuant to the District of Columbia Official Code.”31




      30
           See also Samson v. California, 547 U.S. 843, 853 (2006) (“[A] State’s
interests in reducing recidivism and thereby promoting reintegration and positive
citizenship among probationers and parolees warrant privacy intrusions that would
not otherwise be tolerated under the Fourth Amendment.” (citing Griffin, 483 U.S.
at 879; Knights, 534 U.S. at 121)).
      31
         D.C. Code § 24-133(c)(1) (2012 Repl. & 2018 Cum. Supp.); see Hunt v.
United States, 109 A.3d 620, 621 (D.C. 2014).
                                           24

      To carry out that charge, CSOSA was directed by law to “[d]evelop and

operate intermediate sanctions” for probationers and other sentenced offenders

under its supervision. 32 The regulations that CSOSA promulgated to that end are

the counterpart to the regulation at issue in Griffin. 33 They provide that if a

Community Supervision Officer (CSO) has “reason to believe” a supervisee is

“failing to abide by the general or specific conditions of release” or is “engaging in

criminal activity,” the CSO may address the problem by imposing one or more

administrative sanctions. 34 We explained the advantages of this option in Hunt as

follows:


              Sanctions “can be applied short of court or USPC [Parole
              Commission] approval” and enable CSOSA to “provide
              swift, certain, and consistent responses to noncompliant
              behavior.” . . . “Imposing the sanctions quickly and
              consistently may prevent escalation of the offender’s
              non-compliant behavior.” . . . [B]y issuing sanctions,
              CSOSA “introduce[s] an accountability structure into the
              supervision process” without commencing revocation
              proceedings or seeking a hearing for a change in release
              conditions.”[35]

      32
           D.C. Code § 24-133(b)(2)(F).
      33
           See 28 C.F.R. § 810.3 (2003).
      34
           Id. at § 810.3(a).
      35
         Hunt, 109 A.3d at 621-22 (quoting Community Supervision:
Administrative Sanctions, 68 Fed. Reg. 19738-01 (Apr. 22, 2003)).
                                         25

These advantages echo Griffin’s concerns that requiring a warrant would “interfere

to an appreciable degree with the probation system,” “make it difficult for

probation officials to respond quickly to evidence of misconduct,” and “reduce the

deterrent effect that the possibility of expeditious searches would otherwise

create.” 36



       The administrative sanctions available to the CSO include “[e]lectronic

monitoring for a specified period of time.” 37 This is the provision under which

CSOSA utilizes GPS tracking technology. Like the other enumerated sanctions,

GPS tracking is intrusive, but it directly serves the primary purposes of probation

supervision. As was proffered to the motions judge in the proceedings below,

CSOSA’s website publicized and explained its use of GPS monitoring of its

highest-risk offenders for these purposes as follows:


               CSOSA uses Global Positioning System (GPS) satellite
               monitoring for the highest-risk offenders as part of a
               series of graduated sanctions or as a special condition

       36
            Griffin, 483 U.S. at 876.
       37
          28 C.F.R. § 810.3(b)(6). Other authorized administrative sanctions listed
in § 810.3(b) include daily check-ins, increased drug testing and drug abuse
assessments, community service and increased group activities, placement in a
residential sanctions facility or residential treatment facility, and restrictions on
travel.
                                      26

            imposed by the releasing authority. GPS monitoring is
            used to enforce curfews, establish prohibited/restricted
            areas, and assess and monitor offender movement in the
            community. Depending on the type of GPS technology
            employed with a particular offender, monitoring can be
            performed on an almost real-time basis.


                                    * * *


            This effective tool allows CSOSA to provide heightened
            supervision of high-risk offenders while allowing such
            offenders to productively rehabilitate in the community.

            On any given day, at least 100 offenders are on GPS
            monitoring. . . . GPS placements typically last between
            14 and 90 days.

            CSOSA staff work daily with the DC Metropolitan
            Police Department (MPD) and other law enforcement
            agencies to match offender GPS coordinates with crime
            locations. Mapping technology allows CSOSA to create
            extremely detailed maps of locations and offender
            movements to aid in suspect apprehension and
            identification of witnesses. CSOSA has trained and
            provided MPD staff with direct access to the GPS system
            for monitoring purposes. MPD’s Intelligence Fusion
            Division, responsible for the collection, analysis, and
            dissemination of information related to violent crimes
            within the District of Columbia, is a regular user of
            CSOSA’s GPS data.[38]

      38
           “Electronic Monitoring, Court Services and Offender Supervision
Agency      for    the   District    of    Columbia”      (May     5,    2016),
http://www.csosa.gov/supervision/accountability/monitoring.aspx. This page was
available on the website when Mr. Jackson was placed on probation and being
monitored. Although the page has since been removed, similar information is now
available on CSOSA’s website in its May 7, 2009, Policy Statement 4008; see
                                                                  (continued…)
                                        27

          3. The Reasonableness of CSOSA’s Placement of Mr. Jackson on
GPS Monitoring


      While probation supervision “is a ‘special need’ . . . permitting a degree of

impingement upon privacy that would not be constitutional if applied to the public

at large[,] [t]hat permissible degree is not unlimited.”39 The “impingement” upheld

in Griffin was a warrantless “special needs” search of a probationer’s home, as

authorized by the probation department’s regulations, based on reasonable grounds

to suspect the presence there of contraband. In this case, the “impingement” was

the warrantless attachment and use of a GPS tracking device, as authorized by

CSOSA’s regulations, based on reasonable grounds to suspect a probationer might

be committing new crimes. (Mr. Jackson was not subject to a curfew or a stay-

away order.) The Fourth Amendment reasonableness inquiry requires us to weigh

the extent to which such a search violates a probationer’s reasonable privacy




(…continued)
footnote 2, supra. We note that, regardless of the utilization of CSOSA’s GPS
data by the police, the Policy Statement provides that CSOs are responsible for
reviewing the GPS tracks of offenders under their supervision on a daily basis, and
for investigating, reporting, and sanctioning any violations.

       We address the propriety of CSOSA’s sharing of its GPS data with the MPD
in Part II.B of this opinion.
      39
           Griffin, 483 U.S. at 875.
                                        28

expectations against CSOSA’s special need to be able to impose such a sanction to

supervise noncompliant, high-risk probationers.



      We begin by acknowledging that GPS monitoring can be a serious intrusion

on personal privacy.     Attachment of the GPS device is a trespass on the

probationer’s person. Having to maintain the device is a chore that somewhat

curtails the probationer’s activities and freedom of movement. Mr. Jackson’s GPS

contract, for example, did not allow him to bathe or go swimming, and it required

him to be inactive for two hours every day while charging the device. Beyond that,

the Supreme Court has recognized that “individuals have a reasonable expectation

of privacy in the whole of their physical movements,” including those in the public

domain.40     Activities carried on in public are not private by definition and,

generally speaking, no reasonable expectation of privacy attends them; but the

government’s prolonged, minute-by-minute tracking and recording of all of a

person’s movements and whereabouts is another matter.41            Such intensive


      40
            Carpenter v. United States, 138 S. Ct. 2206, 2217 (2018) (emphasis
added).
      41
           See Jones, 565 U.S. at 430 (Alito, J., joined by three other Justices,
concurring in the judgment) (“[R]elatively short-term monitoring of a person’s
movements on public streets accords with expectations of privacy that our society
has recognized as reasonable. But the use of longer term GPS monitoring in
investigations of most offenses impinges on expectations of privacy.”).
                                       29

surveillance is unusual and, under normal circumstances, is contrary to the

ordinary person’s privacy expectations because it has the potential to open “an

intimate window into a person’s life, revealing not only his particular movements,

but through them his ‘familial, political, professional, religious, and sexual

associations.’” 42



       It also must be acknowledged, however, that “nothing of that kind is

involved in this case.” 43 By itself, CSOSA’s GPS monitoring “just identifies

locations; it doesn’t reveal what the wearer of the device is doing at any of the

locations.”44 So far as appears, CSOSA follows internal procedures to ensure that

GPS monitoring is appropriate, and the tracking data is reviewed solely to

determine whether supervisees were present at crime scenes or prohibited

locations, or were violating curfews. When confined to that use, GPS monitoring




       42
       Carpenter, 138 S. Ct. at 2217 (quoting Jones, 565 U.S. at 415 (opinion of
Sotomayor, J.)).
       43
            Belleau v. Wall, 811 F.3d 929, 935 (7th Cir. 2016) (upholding
constitutionality of statute requiring persons released from civil commitment for
sex offenses to wear a GPS monitoring device 24 hours a day for the rest of their
lives).
       44
            Id. at 936.
                                         30

is far less of an intrusion on a supervisee’s privacy than, for example, the

warrantless search of a private home sanctioned in Griffin.45



      As the Supreme Court emphasized in Griffin and subsequent cases, the

reasonable privacy expectations of a probationer are not the same as those enjoyed

by the ordinary citizen; an offender under precautionary and rehabilitative

supervision on release in lieu of incarceration must expect considerable

supervisory intrusion on his privacy. Offenders placed on probation in Superior

Court are informed of what kinds of intrusions to expect. The conditions of Mr.

Jackson’s probation warned him that he would have to accept (among other

requirements) home visits by his CSO, drug testing at CSOSA’s discretion, and –

of particular pertinence to this case – the “program of graduated sanctions” to

which his conduct on probation might subject him. CSOSA’s regulations and

procedures require offenders to enter into “accountability contracts” at the outset of

their probation, in which they expressly acknowledge their probation

responsibilities and the specified administrative sanctions, including GPS

monitoring, to which they will be subject for violating the conditions of their


      45
          See Payton v. New York, 445 U.S. 573, 585 (1980) (“[T]he ‘physical
entry of the home is the chief evil against which the wording of the Fourth
Amendment is directed.” (internal quotation marks omitted)).
                                        31

supervision.46 Thus, probationers like Mr. Jackson are on notice and agree that

they will be subject to intensive and intrusive supervision, specifically including

GPS monitoring, if there is reason to believe they are engaging in criminal activity

while on probation or otherwise violating the conditions of their release. 47 Mr.

Jackson’s subsequent, albeit reluctant, acceptance of his GPS monitoring contract

manifested his awareness that his supervision could include such an intrusion and

thereby confirmed his “severely diminished expectation of privacy” with respect to

such monitoring.48



      CSOSA’s disclosed use of electronic monitoring is calculated to be less

invasive of the probationer’s privacy than prolonged secret surveillance would be.

      46
         See 28 C.F.R. 810.2 (c); Policy Statement 4004, effective November 8,
2006, “Accountability Contract,” https://www.csosa.gov/wp-content/uploads/bsk-
pdf-manager/2018/03/4004_accountability_contract_110806.pdf (last visited June
13, 2019).
      47
        Mr. Jackson’s accountability contract is not included in the record before
us, however.
      48
          United States v. Newton, 369 F.3d 659, 665 (2d Cir. 2004) (quoting
United States v. Reyes, 283 F.3d 446, 461 (2d Cir. 2002)); see also Samson, 547
U.S. at 852 (“In Knights, we found that acceptance of a clear and unambiguous
search condition ‘significantly diminished Knights’ reasonable expectation of
privacy.’” (quoting Knights, 534 U.S. at 120)); United States v. Lambus, 897 F.3d
368, 410 (2d Cir. 2018) (supervisee’s signing of GPS monitoring agreement “is
inconsistent with either a legitimate or a reasonable expectation of privacy
protecting him from constant search via GPS”).
                                         32

The probationer’s awareness that his movements will be tracked for a limited

period of time makes it less likely that the surveillance will be utilized for

improper purposes or otherwise abused. Knowledge of the monitoring enables the

probationer to exercise some control over how much of his personal life is

potentially exposed, and to apply to the court for relief if he believes the

monitoring is unjustified, excessive, or otherwise objectionable.      Mr. Jackson

could have exercised the option of applying to the court for relief from the

monitoring had he wished to do so.49 Alternatively, Mr. Jackson could have

refused to accept installation of the GPS device, in which case CSOSA would have

presented the issue to the court itself by moving to revoke or amend Mr. Jackson’s

probation.



      The infringement on Mr. Jackson’s reasonable privacy expectations must be

balanced against CSOSA’s legitimate supervisory needs in his case and the extent

to which the imposition of GPS monitoring promotes the governmental interests in

deterring recidivism and encouraging Mr. Jackson’s reformation. This side of the

ledger weighs heavily in favor of the search’s reasonableness. CSOSA’s criteria

      49
          See D.C. Code § 24-304 (a) (2012 Repl. & 2018 Cum. Supp.) (“At any
time during the probationary term the court may modify the terms and conditions
of the order of probation, . . . when in the opinion of the court the ends of justice
shall require . . . .”).
                                         33

for placement of supervisees on GPS tracking reasonably limit its use to high-risk

offenders whose behavior under less intensive supervision demonstrably supports

the need to monitor them more closely. CSOSA reasonably determined that Mr.

Jackson met those criteria, as he was on probation for a robbery, he had been re-

arrested (apparently for another robbery), and he had not been complying with his

supervisory conditions. CSOSA had ample reason to deem him at high risk of re-

offending with another violent felony and to find it appropriate to institute GPS

tracking of his movements to deter him. It cannot plausibly be maintained that the

intrusion of GPS tracking was disproportionate to the threat Mr. Jackson posed to

the safety of the community.



      Mr. Jackson’s objection, that CSOSA put him on GPS monitoring at the

urging of the police because they suspected him of continuing to commit robberies,

is not well taken. Even if CSOSA’s decision was influenced by that information

and request, Griffin deemed it “reasonable to permit information provided by a

police officer . . . to support a probationer search,” 50 and it is well-settled that

probation officers are permitted to collaborate with the police “as long as the

probation officers are pursuing legitimate probation-related objectives” in doing


      50
           483 U.S. at 879-80.
                                            34

so.51 Here, while the police request was evidently what led CSOSA to consider

placing Mr. Jackson on GPS monitoring, the record shows that CSOSA did so only

after determining that he met its own criteria for employing GPS monitoring to

further the objectives of his probation supervision.



      In addition, the record before us lends no support to Mr. Jackson’s assertion

that CSOSA put him on GPS monitoring so that the police could “use that

surveillance for the purpose of its robbery investigation.”52 There is no evidence

that CSOSA informed the police it had begun tracking Mr. Jackson’s movements,

and no evidence that the police used his GPS surveillance to investigate his

potential involvement in robberies other than the one at hand. In the present case,

of course, Mr. Jackson was not initially identified as a suspect and Detective

O’Donnell’s initial query of the GPS database did not target him at all; the police

simply entered the coordinates of the reported robbery and inquired whether

anyone monitored by CSOSA had been at the scene.



      As the facts of this case illustrate, GPS tracking is a uniquely valuable and

effective tool for detecting whether a high-risk offender is committing crimes,
      51
           Reyes, 283 F.3d at 464 (citing cases).
      52
           Brief for Appellee at 29 n.18.
                                          35

going to prohibited places, or violating curfew, and—because the inquiry of the

data can be and is selectively limited to those questions—for doing so without

unnecessarily intruding into the offender’s other activities at all. For the reasons

identified in Griffin and Hunt, CSOSA’s ability to employ such focused GPS

monitoring as an intermediate sanction without judicial approval promotes

legitimate governmental interests in responsive, effective, and commensurate

supervision of high-risk offenders on probation. As this court recognized in Hunt,

“sanctions are an alternative to requesting a hearing that ‘may result in . . . changes

to the conditions of [a probationer’s] release.’” 53 Like the Supreme Court in

Griffin, we think little if anything would be gained in most cases by “setting up a

magistrate rather than the probation officer as the judge of how close a supervision

the probationer requires” from time to time. 54 It is telling that, in the present case,

although Mr. Jackson complains that CSOSA did not seek judicial approval of its

decision to put him on GPS monitoring, he has not argued that the decision was

unjustified by his behavior on probation, nor has he identified any reason a judge

might have disagreed with it in his case. As we have said, judicial review of a




      53
           109 A.3d at 623 (quoting 28 C.F.R. § 810.3(a) (2014)).
      54
           483 U.S. at 876.
                                        36

questionable decision to initiate GPS monitoring is available to a probationer. Mr.

Jackson did not seek such review.



      Although a court may have reason in some cases to make compliance with

GPS monitoring an express condition of probation at the time the court imposes

sentence, such an express condition is not a constitutional prerequisite for the

probationer to be subjected to a monitoring requirement if his behavior on

probation calls for it as a reasonable sanction.55 The need for a GPS monitoring

requirement is not something that can be predicted accurately at the time of

sentencing; unanticipated circumstances may arise and justify CSOSA’s

employment of that tool as an intermediate and hopefully temporary sanction.



      In our view, the limited nature and degree of the intrusion by GPS

monitoring on Mr. Jackson’s privacy was outweighed by the extent to which that

intrusion was needed to promote the government’s legitimate and important

interests in the effective supervision of a high-risk probationer. Like the Supreme

Court in Griffin, we therefore conclude that CSOSA’s placement of Mr. Jackson

on GPS monitoring pursuant to its regulations governing probationers was a

      55
          In Griffin, for example, the Court upheld the warrantless search of a
probationer’s home even though no condition of probation authorized it.
                                        37

reasonable search within the meaning of the Fourth Amendment. It is on this

premise that we now turn to consider the ruling that the MPD’s access to Mr.

Jackson’s GPS tracking data violated his Fourth Amendment rights because he

retained an undiminished expectation of privacy in that data with respect to the

police.



      B. CSOSA Did Not Violate Mr. Jackson’s Reasonable Expectation of
Privacy by Sharing His GPS Data with the Police for Legitimate Compliance-
Related Purposes.


      In concluding that the police violated Mr. Jackson’s reasonable expectation

of privacy in his GPS data, the motions judge relied on the Supreme Court’s

analysis in Knights of a warrantless search of a probationer’s residence by the

police.    Because that search was independent of the probation department’s

exercise of supervision over the probationer, it was not justified by Griffin’s

“special needs” rationale. The Supreme Court upheld the police search in Knights

on a different rationale, one grounded on the “salient” fact that a condition of Mr.

Knights’s probation explicitly required him to submit to a search at any time,

without cause, by either a probation officer or a law enforcement officer.56 By

virtue of his knowing acceptance of that search condition, the Court held, Mr.

      56
           534 U.S. at 118.
                                        38

Knights’s reasonable expectation of privacy as a probationer was so “significantly

diminished” that the police constitutionally could search his home without a

warrant based on “no more than reasonable suspicion” of criminal activity there.57



      In the present case, the judge noted that Mr. Jackson’s GPS contract with

CSOSA contained “no clear and unambiguous search condition allowing MPD

access.” The conditions of Mr. Jackson’s probation were “similarly devoid of any

reference to the MPD.” Consequently, the judge stated, Mr. Jackson’s “reasonable

expectation of privacy as to the MPD was not diminished” (emphasis added). On

that premise, the judge proceeded to balance the intrusion of GPS monitoring on

Mr. Jackson’s entirely undiminished expectation of privacy in his movements

against “the MPD’s general interest in criminal investigation,” inasmuch as “it was

the MPD, and not CSOSA, who carried out the search in the course of

investigating a crime.” The judge concluded that “[b]ecause the MPD’s search of

      57
           Id. at 121. Although Mr. Knights’s probation condition purported to
authorize searches without any individualized suspicion at all, the Court found it
unnecessary to address the constitutionality of a suspicionless search because the
search in the case before it was supported by reasonable suspicion. Id. at 120 n.6.
Later, in Samson, the Court held that the Fourth Amendment does not prohibit a
police officer from conducting a suspicionless search of a parolee subject to a
release condition explicitly authorizing such a search. 547 U.S. at 847. In arriving
at that conclusion, the Court observed that “parolees have fewer expectations of
privacy than probationers, because parole is more akin to imprisonment than
probation is to imprisonment.” Id. at 850.
                                        39

Jackson’s GPS location information was neither based on any level of

individualized suspicion[58] nor conducted pursuant to a clear and unambiguous

search condition, Jackson’s intact reasonable expectation of privacy as to the MPD

outweighs the government’s interest. . . .      The MPD search was therefore

unreasonable under the Fourth Amendment.”



      We perceive several questionable features of this analysis. For one thing,

the judge’s weighing does not seem to take into account the quite limited scope of

the actual intrusion by the police on Mr. Jackson’s privacy, nor the fact that once

the police discovered he was at the scene of the robbery, they had ample

individualized suspicion that he committed the robbery – points to which we shall

return below.   For another thing, although the Supreme Court relied on the

existence of an explicit search condition to uphold the search of a probationer’s

residence in Knights, it does not necessarily follow that (as the motions judge




      58
          The judge noted that the police “made no effort to determine whether
there was a sufficiently high probability that Jackson committed the robbery”
before turning to the GPS records of CSOSA’s monitored supervisees “as a tool for
criminal investigation.”
                                         40

appears to have reasoned) such an explicit condition is always necessary to

diminish a probationer’s reasonable expectation of privacy in his movements. 59



      Most important, we think the judge’s analysis overlooks a critical distinction

between Knights and the present case. Unlike in Knights, the intrusion on Mr.

Jackson’s expectation of privacy to acquire the incriminating evidence was

performed, in the first instance, in the course of his probationary supervision. It

was CSOSA, not the police, that attached the device and collected Mr. Jackson’s

GPS data for its own compliance-related purposes, in what we have concluded was

a constitutional search; and (again, unlike in Knights) it was CSOSA’s decision to

grant the police access to that collected data. We therefore think the Fourth

Amendment issue is properly framed differently from the way the motions judge

framed it. The constitutional issue in our view is whether Mr. Jackson had an

objectively reasonable expectation that CSOSA would not share his GPS data with

the MPD. For the reasons that follow, we conclude that such an expectation would

not have been reasonable.

      59
           The judge drew the dubious conclusion that “it is not the individual’s
status as a probationer that diminishes his expectation of privacy. Rather, it is the
search condition, permissible due to probationer status, that diminishes the
individual’s expectation of privacy.” But see Knights, 534 U.S. at 119 (“Inherent
in the very nature of probation is that probationers do not enjoy the absolute liberty
to which every citizen is entitled.” (quotation marks and citations omitted)).
                                       41

      CSOSA granted the MPD access to its supervisees’ GPS monitoring data

(and received access to the MPD’s locational and temporal data pertaining to

crimes, arrests, and other law enforcement activities) pursuant to a longstanding

information-sharing agreement between the two agencies. Their Memorandum of

Understanding (MOU), an exhibit in the proceedings below, explains that CSOSA

and the MPD “share a common mission to reduce and prevent crime,” and that a

purpose of their two-way automated and routine data sharing arrangements is “to

enhance CSOSA’s ability to prevent supervised offenders from engaging in

criminal activity, thereby reducing recidivism and improving public safety, in

accord with the agency’s mission.” The MPD’s detection of criminal activity by

CSOSA’s supervisees and enforcement of the law against them serves CSOSA’s

supervisory goals as well as the MPD’s own law enforcement ends. To help

achieve CSOSA’s supervisory goals, the MPD’s data-sharing commitments to

CSOSA extend to providing electronic notification whenever one of CSOSA’s

supervised offenders is “matched to an MPDC arrest event,” and in other ways

enabling CSOSA personnel to determine whether information and intelligence in

police databases “will affect an offender’s supervision level or other aspects of

CSOSA case management.”
                                         42

      As CSOSA and the MPD agreed in the MOU, their data sharing is subject to

their compliance with applicable District of Columbia and federal law governing

the confidentiality of the information, specifically including (as pertinent here) the

Privacy Act, 5 U.S.C. § 552a (2014).60        Thus, the MOU provides that data-

connectivity is contingent on CSOSA’s publication of a “routine use” Privacy Act

notice in the Federal Register stating that its records may be disseminated to law

enforcement agencies “to assist in the general crime prevention and detection

efforts of the recipient agency or to provide investigative leads to such agency.”

Accordingly, in 2006, CSOSA published a notice in the Federal Register stating it

would treat as a routine use the disclosure of “electronic monitoring information,”

including “Global Positioning System (GPS) data,” to the MPD and other law

enforcement agencies that “require[] information relevant to a civil or criminal

investigation to the extent necessary to accomplish their assigned duties unless

      60
           The Privacy Act provides, in pertinent part, that “[n]o agency shall
disclose any record which is contained in a system of records by any means of
communication to any person, or to another agency, except . . . with the prior
written consent of[] the individual to whom the record pertains, unless disclosure
of the record would be . . . (3) for a routine use as defined in subsection (a)(7) of
this section and described under subsection (e)(4)(D) of this section.” 5 U.S.C. §
552a(b) (emphasis added). The term “routine use” is defined to mean, “with
respect to the disclosure of a record, the use of such record for a purpose which is
compatible with the purpose for which it was collected.” Id. § 552a(a)(7).
Subsection (e)(4)(D) provides for agency publication in the Federal Register of
“each routine use of the records contained in the system, including the categories
of users and the purpose of such use.”
                                         43

prohibited by law or regulation” or “to assist in the general crime prevention and

detention efforts of the recipient agency or to provide investigative leads to such

agency.” 61



      CSOSA made no secret of its sharing of GPS monitoring data with the

police. As previously noted in Section II.A of this opinion, CSOSA publicized on

its website the MPD’s use of its GPS tracking data to “aid in suspect

apprehension.”



      In view of CSOSA’s established and publicly-declared practice of sharing its

GPS tracking data with the MPD as a routine use permitted by the Privacy Act, it is

difficult to see how Mr. Jackson could have expected otherwise. CSOSA was

under no legal obligation to withhold its supervisees’ GPS tracking data from the

      61
          71 Fed. Reg. 58, pp. 15177-78 (Mar. 27, 2006); see also 74 Fed. Reg.
158, pp. 41689-90 (Aug. 18, 2009). The release of parole supervision records to
further a criminal investigation has been held to qualify as a routine use under the
Privacy Act, see United States v. Miller, 643 F.2d 713, 715 (10th Cir. 1981), and it
is not suggested that probation supervision records should be treated differently in
this respect. We think it clear that CSOSA’s disclosure of the GPS tracking data to
the MPD and other law enforcement agencies is for purposes that are “compatible”
with the purposes for which CSOSA collected that data. Cf. Kimberlin v. United
States Dep’t of Justice, 788 F.2d 434, 437-38 (7th Cir. 1986) (upholding disclosure
of federal prison inmate’s information to probation officer as a routine use under
the Privacy Act, because “[a] probation officer is clearly a law enforcement official
as the term is ordinarily used”).
                                         44

police. It did not tell Mr. Jackson it would do so; nor does he claim to have

received such an assurance of confidentiality from the court or any other source.

In point of fact, as far as we are aware, nothing in the record indicates Mr. Jackson

actually was surprised to learn CSOSA had shared his GPS tracking data with the

MPD. If anything, Mr. Jackson’s dismayed remark to his CSO – that “he wouldn’t

be able to do anything” after the GPS device was attached to his ankle – suggests

he foresaw the possibility.



      In any event, an expectation on Mr. Jackson’s part that CSOSA would not

voluntarily share his GPS data with the police for their mutual, compliance-related

purposes would have been objectively unreasonable.         A primary objective of

probationary supervision is “the protection of society from future criminal

violations.”62   Cooperation with and enlistment of the police are means of

accomplishing that objective. A probation officer is, as the Supreme Court has put

it, “a peace officer, and as such is allied, to a greater or lesser extent, with his

fellow peace officers.” 63 An offender on probation “cannot pretend ignorance” of

that fact, and “[a]bsent some express or implied promise to the contrary, he may


      62
           Washington v. United States, 8 A.3d 1234, 1235 (D.C. 2010).
      63
           Fare v. Michael C., 442 U.S. 707, 720 (1979).
                                         45

also be charged with knowledge that the probation officer is duty bound to report

wrongdoing by the probationer when it comes to his attention, even if by

communication from the probationer himself.”64



      The same principle applies to sharing evidence of a probationer’s possible

wrongdoing, including his whereabouts while under supervisory GPS tracking. As

a general rule, courts have held that law enforcement agencies do not violate

reasonable expectations of privacy or Fourth Amendment limitations by sharing

evidence and information they have acquired in lawful searches and seizures with

other law enforcement agencies for legitimate law enforcement purposes.65 More

to the point, it is well-settled that, because “the objectives and duties of probation

officers and law enforcement personnel are often parallel and frequently

intertwined[,] the law permits cooperation between probation officers and other

law enforcement officials so that they may work together and share information to

      64
          Minnesota v. Murphy, 465 U.S. 420, 432 (1984) (internal punctuation and
citations omitted).
      65
          See, e.g., United States v. Jenkins, 496 F.2d 57, 73 (2d Cir. 1974)
(approving of local police allowing federal agents to examine, for a bank robbery
investigation, the serial numbers of dollar bills that the local police collected from
the appellant at the time of his arrest on a gun charge); United States v. Gargotto,
476 F.2d 1009, 1014 (6th Cir. 1973) (“Evidence legally obtained by one police
agency may be made available to other such agencies without a warrant, even for a
use different from that for which it was originally taken.”).
                                         46

achieve their objectives.” 66 In Griffin the Supreme Court clearly implied, and

other courts have held, that probation officers may share the lawfully-obtained

fruits of probation searches with the police even if it would not have been lawful

for the police to conduct the searches themselves. 67



      One of CSOSA’s legitimate objectives is to detect the presence of its high-

risk supervisees at the scenes of criminal activity by comparing their GPS tracking

data with crime location data supplied by the MPD for that purpose.

Individualized suspicion linking particular supervisees to particular crimes is not a

precondition for CSOSA to conduct such narrowly targeted data searches; the point


      66
          Reyes, 283 F.3d at 471; see also United States v. McFarland, 116 F.3d
316, 319 (8th Cir. 1997) (stating that “[p]arole and police officers may work
together, . . . provided the parole officer is pursuing parole-related objectives”);
United States v. Martin, 25 F.3d 293, 296 (6th Cir. 1994) (“[P]olice officers and
probation officers can work together and share information to achieve their
objectives.”).
      67
          See, e.g., Lambus, 897 F.3d at 407, 409, 412 (approving state parole
officer’s sharing of GPS tracking information with federal law enforcement agents
for a federal investigation because such cooperation was “rationally and reasonably
related to” the parole officer’s interest in preventing parolees “from engaging in
new criminal activity”); Newton, 369 F.3d at 668 (“[I]n United States v. Reyes, 283
F.3d at 463-64, we approved coordinated activities between probation/parole
officers and other law enforcement officials in furtherance of legitimate
supervision objectives even though the specific conditions of supervision there at
issue provided for residential intrusions only by a probation officer, with no
mention of other law enforcement officials.”).
                                        47

of GPS monitoring is to discourage its supervisees from engaging in criminal

activity and to discover whether grounds for suspicion exist. When the monitoring

implicates a supervisee in criminal activity, nothing in the Fourth Amendment

forbids CSOSA from reporting that information to law enforcement. Presumably,

if Mr. Jackson’s CSO had learned from his GPS tracking data before the police did

that Mr. Jackson was present when Mr. Parker and Ms. Pleasant were robbed at

gunpoint, the CSO would have so informed the police. None of that would have

violated Mr. Jackson’s reasonable expectations of privacy in his whereabouts.



      What happened in this case is not materially different – CSOSA allowed the

police to access its GPS tracking database to obtain directly the same limited

information regarding its monitored supervisees’ presence at crime locations that

CSOSA could obtain and hand over to the police. We see no reason to question

CSOSA’s judgment that this furthered its legitimate supervisory objectives. As

this very case illustrates, the police may be able to take appropriate law

enforcement action more quickly, efficiently, and effectively than CSOSA can.



      There is no evidence in this case that CSOSA’s sharing of its GPS tracking

data with the MPD exposes monitored supervisees to a materially greater intrusion

on their privacy, or to a materially different use of the information gained. The
                                         48

police did not use Mr. Jackson’s GPS data to pry into his intimate or private affairs

or the details of his personal life. They sought and obtained limited information

and properly used it for law enforcement purposes. At the outset, the police sought

to learn only whether any monitored supervisee was at the scene of the crime when

it occurred. The police learned absolutely nothing about any supervisees who were

not at the scene; their privacy was not invaded in any way. As for Mr. Jackson, the

GPS data revealed only that he was at the crime scene – a public space in which he

had no reasonable expectation of privacy.             That information provided

particularized suspicion (if not, indeed, probable cause) for the police to believe

Mr. Jackson was one of the robbers, and ample justification for the police to track

his public movements in the minutes immediately following the crime so that he

would not escape or dispose of evidence. 68       Mr. Jackson did not possess a




      68
          Although we do not think the police were obliged to apply for a search
warrant in order to track Mr. Jackson’s flight after they discovered he was present
at the scene of the robbery, we note that the existence at that point of exigent
circumstances provided an alternative justification for proceeding without a
warrant. See Carpenter, 138 S. Ct. at 2223-24 (explaining that although the
government will “generally” need a warrant to access cell-site location information
comparable to GPS data, the exigencies of the situation may render it objectively
reasonable to collect the information without a warrant; “[s]uch exigencies include
the need to pursue a fleeing suspect, . . . or prevent the imminent destruction of
evidence”).
                                        49

reasonable expectation that those movements would be private.69 The police use of

his GPS data did not extend beyond that tracking. While long-term GPS tracking

impinges significantly on a person’s expectation of privacy in his movements,

there was nothing long-term about the police tracking of Mr. Jackson; it was as

brief as it could possibly have been. Although the police learned that Mr. Jackson

fled into an apartment (it is unclear whether they knew or had reason to believe it

was Mr. Jackson’s residence), the tracking disclosed nothing about his activities

inside it.   In short, any intrusion by the police on Mr. Jackson’s reasonable

expectation of privacy was de minimis, in our view, and far outweighed by its

public benefits. Mr. Jackson has no grounds to complain that the police, by

resorting to his GPS data in the immediate aftermath of the armed robbery, were

able to arrest him more swiftly and recover corroborative physical evidence that

otherwise might have been lost.       If that was so, it only underscores the

reasonableness of CSOSA’s sharing of the data with the police.



      Mr. Jackson argues that CSOSA’s sharing of its GPS tracking data with the

police for use in law enforcement is at odds with the Supreme Court’s decision in


      69
           See United States v. Knotts, 460 U.S. 276, 281 (1983) (“A person
traveling in an automobile on public thoroughfares has no reasonable expectation
of privacy in his movements from one place to another.”).
                                        50

Ferguson v. Charleston.70 We do not agree. In Ferguson, the Court held that a

public hospital violated its patients’ Fourth Amendment rights if, in testing them

for illegal drug use as part of their medical care, the hospital did so with the

undisclosed objective of obtaining incriminating evidence and sharing it with law

enforcement for purposes of prosecuting the patients. That case is not comparable

to this one. The persons subject to the searches in Ferguson were “typical”

hospital patients with typical, undiminished privacy expectations.      The Court

recognized that they reasonably expected the hospital would not voluntarily share

their personal and private medical test results with outsiders for a non-medical use

such as criminal prosecution unless the hospital had their informed consent to do

so.71        In contrast, CSOSA’s supervisees are convicted probationers with

significantly diminished expectations of privacy in their activities; they are aware

CSOSA collects their GPS tracking data with a law enforcement objective; and

having that awareness, they cannot reasonably expect CSOSA to withhold the GPS



        70
             532 U.S. 67 (2001).
        71
         Id. at 78. Not insignificantly, however, the Court distinguished
circumstances in which state hospital employees are legally obligated to report
evidence of criminal conduct acquired in the course of providing medical care.
The Court noted that the existence of reporting laws might bear on the patients’
reasonable expectations of privacy in their personal information. Id. at 78 n.13,
80-81
                                         51

data from other agencies that share CSOSA’s objective and will utilize the data to

further it.



       We conclude that CSOSA did not violate Mr. Jackson’s reasonable

expectation of privacy by granting the police access to his GPS tracking data in

furtherance of their mutual law enforcement objectives.         The limited police

utilization of that access comported with the reason CSOSA granted it and did not

unreasonably intrude on Mr. Jackson’s privacy. We therefore conclude that Mr.

Jackson’s Fourth Amendment rights were not violated.



       We emphasize that we have considered in this opinion only whether the

police violated Mr. Jackson’s Fourth Amendment rights by the limited inspection

and use they actually made of his GPS tracking data. We uphold a narrowly

tailored resort by the police to the GPS data in the absence of articulable suspicion

– the same check to determine whether a monitored probationer was at the scene of

the crime when it occurred that CSOSA itself routinely and permissibly performs,

likewise without articulable suspicion. In doing so, we recognize the sensitivity of

GPS tracking information and do not dismiss privacy concerns about its

susceptibility to possible abuse by overzealous investigators. But no abuse is

revealed by the record before us in this case and, particularly when the question is
                                     52

a constitutional one, “[c]ourts should not decide more than the occasion

demands.”72    We therefore refrain from discussing whether the police

hypothetically would violate the Fourth Amendment if they were to explore

CSOSA’s GPS data more extensively or without the valid law enforcement

purpose present in this case.



                                     III.



      For the foregoing reasons, we reverse the order of the Superior Court

granting Mr. Jackson’s motion to suppress electronic and tangible evidence and

remand for further proceedings.




      72
         District of Columbia v. WICAL Ltd. P’ship, 630 A.2d 174, 182 (D.C.
1993) (quotation marks and citation omitted).
