Argument: September 12, 2017
Court for Baltimore City Case Nos. 114094009, 114094010,
114094011, 114094012, 114094013
Barbera, C. J., Greene, Adkins, McDonald, Watts, Hotten,
factfinder at a trial applies common sense drawn from shared
human experience to the evidence to reach a fair
determination of the facts. Some evidence, however, is beyond
the common experience of most people. Expert testimony may be
necessary for the factfinder to decide the significance of
testimony is often required to explain scientific or
technical matters. But expert testimony is not required
simply because one can explain a matter scientifically. For
example, a jury can be expected to readily understand the
significance of testimony that a clock or a thermometer
displayed certain numbers without need for an expert to
explain the scientific phenomenon that underlies the
thermometer or the engineering that powers the clock. But the
jury will need an expert to understand the significance of an
opinion that two biological samples "match" based
upon a statistical analysis involving DNA evidence.
common sense does not change, common human experience does. A
technical marvel of an earlier time may become the everyday
tool of the contemporary person. This case presents the
question whether location information from a GPS device is
more like numbers read from a clock or thermometer or more
like a conclusion reached from the analysis of DNA evidence.
Martaz Johnson,  an officer with the Maryland Transit
Administration ("MTA") police, was charged with
assaulting and raping a young woman shortly after she had
been involved in a traffic accident with an MTA bus.
According to the young woman, Mr. Johnson had responded to
the scene of that accident in his official capacity and drove
her home, where the offense occurred. Among the equipment
that Mr. Johnson carried that evening as part of his job was
a mobile GPS device, which allowed the MTA to keep track of
the locations of its officers.
trial in the Circuit Court for Baltimore City, the State
introduced GPS data from Mr. Johnson's device that
matched the itinerary given by the woman in her testimony at
trial. That evidence was introduced by a custodian of records
of the MTA police.
Mr. Johnson's defense counsel did not appear to dispute
that Mr. Johnson had been present at the locations indicated
in the GPS data, he objected to the Circuit Court's
decision to admit that evidence on several bases. In this
appeal, Mr. Johnson argues that the State should have
presented expert foundation testimony concerning GPS devices
as a prerequisite to the admission of such evidence.
Court of Special Appeals, relying on one of its prior
decisions,  held that a lay juror could understand the
significance of GPS data without expert help and that it was
not necessary for the State to present expert testimony on
GPS devices and data. We agree with the Court of Special
provide the context in which the legal issues before us
arise, we summarize the key testimony at trial and the
procedural path of this case.
Accident and its Immediate Aftermath
victim of the alleged offenses was a 28-year-old woman whom
we shall refer to as Ms. K. After going out with a female
friend on the evening of March 12, 2014, for dinner, drinks,
and dancing, Ms. K. was driving home in the early morning
hours when her car was struck by an MTA bus at the
intersection of Central Avenue and Monument Street in
police officers responded to the scene of the
accident. Mr. Johnson was one of those officers. Ms.
K. testified that Mr. Johnson told her she should not be
driving any more that evening; she agreed to refrain from
doing so because she had been drinking. According to Ms. K.,
Mr. Johnson instructed her to sit in the back of his police
car and said that he needed to "release" her to
someone or else he would have to take her "downtown,
" which Ms. K. interpreted to mean jail.
decided to contact the friend she had been out with, who
lived nearby, in the hope that the friend would retrieve her
and her car. However, Ms. K. was unsuccessful in multiple
attempts to reach her friend by phone. Mr. Johnson then drove
Ms. K. to her friend's home and Ms. K. attempted to call
the friend from the police car, again without success.
According to Ms. K., Mr. Johnson would not allow her to leave
the car to knock on the door.
Johnson Takes Ms. K. Home and Remains There
testified that, after failing to rouse her friend, she sat
crying in the back of the police car. She said that Mr.
Johnson, instead of taking her "downtown" as he had
originally indicated, then drove her to her own home at 708
North Duncan Street in Baltimore City. According to Ms. K.,
while they were en route, Mr. Johnson asked her "what
are you going to do to make this up."
testified that, as she entered her home, Mr. Johnson followed
her in without being invited to do so. According to Ms. K.,
Mr. Johnson asked her whether anyone else lived there, and
she replied that she lived alone. He then used his flashlight
to check whether there was anyone else in the house.
to Ms. K., Mr. Johnson then assaulted and raped her.
Afterwards, she testified, she tried to take a picture of Mr.
Johnson with her cell phone without success. Mr. Johnson took
the phone from her, made her unlock it, and scrolled through
her pictures. He then left the house.
after Mr. Johnson left her home, Ms. K. called 9-1-1 and
reported that she had been raped by a police officer. An
ambulance transported her to a hospital where she underwent a
rape kit examination. At that time Ms. K. was reluctant to be
interviewed by Baltimore City police detectives because she
thought that Mr. Johnson was associated with the Baltimore
City police. She spoke with an attorney acquaintance later
that day who encouraged her to talk to the detectives. When
she was subsequently interviewed by the detectives, she told
them that Mr. Johnson was the officer who had assaulted her.
Johnson later submitted to forensic testing, which revealed
Ms. K.'s skin cells on the shaft of his
Johnson was charged in the Circuit Court for Baltimore City
with first and second-degree rape, third and fourth-degree
sex offenses, first-degree assault, two counts of
second-degree assault, first, third, and fourth-degree
burglary, reckless endangerment, and misconduct in office.
trial, the State presented the testimony of Ms. K., who
recounted the events as summarized above and made an in-court
identification of Mr. Johnson as her assailant. The State
sought to corroborate Ms. K.'s account through other
testimony and evidence. In particular, it called the MTA
police officer who had initially responded to the accident
before Mr. Johnson arrived and who left the scene while Mr.
Johnson was talking with Ms. K. That officer testified that
an MTA police protocol required an officer who planned to
transport a civilian to report that activity to radio
dispatch. He testified that the radio log for that evening
did not reveal such a call by Mr. Johnson.
Baltimore City police detectives who investigated the offense
also testified about their interview of Ms. K. and the
gathering of forensic evidence. The forensic nurse who had
examined Mr. Johnson, the police DNA technician who noted
skin cells on the swabs taken from Mr. Johnson's
genitals, and the DNA analyst who matched the DNA of those
skin cells to Ms. K.'s DNA also testified. The attorney
acquaintance of Ms. K. testified that he had found a
"frantic" message on his phone from Ms. K. the
morning of March 13 in which she stated that she had been
raped by a police officer and that he had counseled her to
talk to the detectives.
State also introduced evidence from a GPS tracking
device known as a "Pocket Cop" that Mr.
Johnson had carried that night. MTA police officers carry
Pocket Cops primarily for officer safety. A Pocket Cop
records GPS data concerning its location and movements.
Police supervisors can access the data from a particular
officer's device through a program called "Field
Force Manager." That program generates a report that
shows the location of a Pocket Cop at specific times and the
duration of time spent at each location. As a result, the MTA
can determine where its officers are, and have been, at any
police supervisor who served as its custodian of records
testified that the data derived from the device carried by
Mr. Johnson on March 13, 2014, showed that he had spent 14
minutes that night in the vicinity of the address of Ms.
K.'s friend and 37 minutes in the vicinity of Ms.
K.'s residence. The evidence and arguments concerning the
admissibility of that data are described in greater detail in
Part II.A of this opinion.
police supervisor also reiterated that it would be contrary
to department policy for an officer to transport a civilian
in the officer's police car without calling a supervisor
over the radio and obtaining permission. He testified that
the radio log for the evening did not show a call by Mr.
Johnson to his supervisor for that purpose.
defense did not call any witnesses and Mr. Johnson exercised
his right not to testify.
Circuit Court granted a judgment of acquittal on charges of
fourth-degree burglary, first-degree assault, third-degree
sex offense, and reckless endangerment. The jury acquitted
Mr. Johnson of first-degree and third-degree burglary, as
well as first-degree rape. It could not reach a verdict on
the charges of second-degree rape and fourth-degree sex
offense. The jury convicted Mr. Johnson of misconduct in
office and two counts of second-degree assault.
Johnson filed a timely appeal to the Court of Special
Appeals, where he raised several legal issues, including the
admissibility of the GPS evidence. The Court of Special
Appeals affirmed the convictions in an unreported opinion on
December 16, 2016.
Johnson then petitioned this Court for a writ of
certiorari on the question of whether the GPS data
was properly admitted without expert testimony. The State
submitted a conditional cross-petition on the question
whether Mr. Johnson had preserved that issue in the Circuit
Court. We granted both petitions.
The GPS Evidence at Trial
legal issues in this appeal concern whether expert testimony
was necessary in order to admit GPS data from the Pocket Cop
device carried by Mr. Johnson on March 13, 2014 and whether
the defense adequately preserved an objection to that
evidence on that basis. Accordingly, it is useful to recount,
in some detail, how that evidence was elicited at trial and
how the defense objections to it were framed.
defense made a motion in limine at the beginning of
the trial to exclude various items of the State's
evidence, but the GPS data from Mr. Johnson's Pocket Cop
was not among those items. Indeed, the theory of the defense
at trial appeared to be consistent with the GPS data derived
from the Pocket Cop device. In his opening statement to the
jury, defense counsel conceded that Mr. Johnson drove Ms. K.
first to her friend's house and then to her own house.
Defense counsel also told the jury that Mr. Johnson had
entered Ms. K.'s house for a period of time, stated that
Ms. K. made an "advance at" Mr. Johnson while they
were inside the house, and denied that Mr. Johnson raped her
during that visit.
Ms. K. testified as the State's first witness, the
defense cross-examination of her was consistent with the
approach taken in its opening statement. Defense counsel had
Ms. K. repeat much of the same testimony that she gave on
direct examination, but suggested that she was attracted to
Mr. Johnson. The theory of the defense appeared to be that
Mr. Johnson had responded to the accident in his official
capacity and that he had taken Ms. K. home in that capacity
as well, but that he had not initiated or consummated any
assault of Ms. K.
concerning the Pocket Cop device was first elicited at the
trial during the defense cross-examination of the MTA police
officer who had initially responded to the accident scene
before Mr. Johnson arrived. Defense counsel adduced testimony
from that officer concerning the function of the Pocket Cop
device. The thrust of the defense cross-examination was that,
even though an MTA radio log indicated that Mr. Johnson had
failed to call in his location when he was transporting Ms. K
(as required by the MTA police protocol), Mr. Johnson's
supervisors would have known where he was because he was
carrying a GPS device.
State later introduced some details concerning the data
recorded by Mr. Johnson's Pocket Cop that evening.
Sergeant William Schauman, an executive officer at MTA police
headquarters, testified that Mr. Johnson was assigned to
cover the area of the bus accident on the night of March
12-13, 2014. Sergeant Schauman explained the function of the
Pocket Cop device and described a report summarizing GPS data
from Mr. Johnson's Pocket Cop for the period from
midnight to noon on March 13, 2014. The State sought to
introduce the GPS report through Sergeant Schauman.
counsel objected to admission of the report. At a bench
conference, defense counsel elaborated that his objection was
based on the fact that Sergeant Schauman had not personally
investigated the matter and that the document was not itself
maintained in the ordinary course of business, but had been
generated from the computer records for purposes of the case.
Defense counsel also argued that the report was incomplete in
that it contained an unexplained "gap" of
time. He contended that the report should be
introduced only by the person who generated it. These
objections appeared to go to authentication of the report and
an assertion that the State had not established a sufficient
foundation for the report itself to come within the business
record exception to the hearsay rule. The Circuit Court initially
reserved its decision on these objections and allowed the
State to ask additional questions of Sergeant Schauman to lay
a foundation for admission of the document.
State then resumed questioning Sergeant to lay a more
complete foundation for admitting the GPS report under the
business record exception to the hearsay rule. Sergeant
Schauman testified that it was standard operating procedure
for MTA officers to carry the device so that their movements
could be tracked while they are on duty. The State again
sought to admit the GPS report into evidence. The defense
objected again and a second bench conference ensued.
Circuit Court observed that, although the witness had not
used the "magic words, " he had essentially
testified that it was the ordinary course of business for the
MTA to track the locations of its officers by means of the
Pocket Cop. Defense counsel then complained that the record
appeared to be incomplete and that the witness would not be
able to speak to the "authenticity or veracity" of
midst of this discussion as to whether the State had laid a
sufficient foundation to satisfy the defense objections as to
authenticity, hearsay, and the completeness of the GPS
report, defense counsel asserted that "this gentleman is
now being offered as a quasi- expert to lay a foundation for
the admission of technical information." The discussion,
however, then returned to whether the GPS data was generated
in the ordinary course of business and, after the Circuit
Court reiterated its finding that it was, the defense did not
further pursue its objection that Sergeant Schauman was being
asked to provide the necessary foundation as a
counsel then questioned whether the entire document would
come into evidence or just specific references in the GPS
report. The Circuit Court agreed that some references in the
report were not relevant, and the State volunteered to simply
ask Sergeant Schauman about specific entries in the report
that were relevant to the trial. The Circuit Court observed
that defense counsel could attack any defects in the GPS
report through cross-examination.
response to questions from the prosecutor, Sergeant Schauman
then read two entries from the report to the jury. He stated
that the first entry indicated that, on March 13, 2014,
beginning at 3:55 a.m., Mr. Johnson was at 1224 Ashland
Avenue - a location near the home of Ms. K's friend - for
14 minutes. He testified that the second entry indicated that
Mr. Johnson was at 710 North Duncan Street - a building next
to Ms. K.'s home - for 37 minutes beginning at 4:10 a.m.
cross-examination, defense counsel asked Sergeant Schauman
various questions about the calibration and accuracy of the
GPS function on the Pocket Cop. Sergeant Schauman responded
that he was "not the technical person" for the
agency. Defense counsel also obtained admissions from
Sergeant Schauman that he could not tell from the GPS report
whether Mr. Johnson had entered a building at either of the
two locations mentioned in his direct testimony. Defense
counsel also questioned Sergeant Schauman about other entries
on the GPS report that had not been covered on direct
examination. The Circuit Court later confirmed that it had
not admitted the entire report.
the discussion of Sergeant Schauman's testimony, the
State suggested that it might call another officer more
knowledgeable about the technical aspects of GPS, but
apparently elected not to do so. The defense never moved to
strike the testimony derived from the GPS report - perhaps
unsurprising as that testimony did not contradict the defense
theory of the case.
closing arguments, the prosecution never mentioned the GPS
data. The defense alluded to it only (1) to reiterate that
Mr. Johnson could not have gone "off the grid" from
his supervisors while he was on duty because he was being
tracked by a GPS device and (2) to point out that the device
did not precisely indicate whether Mr. Johnson was inside Ms.
K.'s house or what he was doing when it showed him in the
vicinity of her house.
initial matter, the State argues that Mr. Johnson did not
adequately preserve for appeal his contention that the State
was required to present expert testimony explaining the
operation of GPS devices as a prerequisite to the admission
of GPS data. "Ordinarily, the appellate court will not
decide any … issue [other than jurisdiction] unless it
plainly appears by the record to have been raised in or
decided by the trial court …." Maryland Rule
true, as the State asserts, that the defense objection to
Sergeant Schauman's testimony concerning the GPS report
appeared, at least initially, to be that the State had not
laid an adequate foundation relating to authentication,
hearsay, and completeness of the report - objections quite
distinct from whether expert testimony is necessary to lay a
foundation for admission. In particular, much of the
discussion focused on whether the report satisfied the
business records exception to the hearsay rule. For example,
at the beginning of each bench conference, defense counsel
argued that the report was not kept in the ordinary course of