United States District Court, D. Hawaii
ORDER DENYING DEFENDANT DEREK HAHN'S MOTION IN
LIMINE TO EXCLUDE EXPERT TESTIMONY, ECF NO. 382
Michael Seabright Chief United States District Judge
Derek Hanh (“Hahn”) seeks an order in limine
excluding FBI Supervisory Special Agent Edwin Nam
(“Nam”) from testifying as an expert witness
regarding historical cell-site data pursuant to Federal Rule
of Criminal Procedure 16 and Daubert v. Merrell Dow
Pharmaceuticals, Inc., 509 U.S. 579 (1993)
(“Daubert I”). On March 13, 2019, the
court held an evidentiary hearing, with Nam as the sole
witness. For the following reasons, the motion is DENIED.
the government's investigation, a warrant was issued to
Sprint Communications for Hahn's cellular telephone
records. Both parties agree that the Sprint records captured
the phone's voice calls and text messaging transactional
data, including the particular cellular tower that the phone
accessed when voice calls and/or text messages were sent or
received. It is also undisputed that the towers at issue in
this case used approximate 120-degree sectors (sometimes
called “faces”) to provide 360 degrees of
coverage per tower. The Sprint records capture not only the
tower used, but also the particular sector that connected at
a particular time.
supervisor at the FBI's cellular analysis survey team,
testified that for each voice call or text message sent or
received, the phone selects the tower that provides the best
signal at that time. The best signal, in turn, is determined by
signal strength and signal quality. Nam was likewise clear
that a cell phone does not always or necessarily utilize the
nearest tower; instead it assesses its environment and uses
the tower with the best signal. For example, he explained
that in a perfectly flat area with no obstructions, the tower
with the best signal would be the nearest to the cell phone.
But various factors can impact which tower offers the best
signal, including obstructions and topography.
on this explanation, Nam testified that once he has
identified a specific Sprint tower and its sector that was
used on a specific date and time, he cannot conclude
specifically where the phone was located, but can testify
that it was used within the coverage area of that specific
tower's sector. Finally, he explained that the coverage
area for each tower is unique, and that he did not measure
the coverage area for each tower identified in this case.
Federal Rule of Criminal Procedure 16
first contends that the government failed to comply with its
discovery requirements under Federal Rule of Criminal
Procedure 16 (“Rule 16”). The court disagrees.
requires the government to provide the defense with “a
written summary” of the testimony it expects to adduce
from an expert witness and that summary must “describe
the witness's opinions, the bases and reasons for those
opinions, and the witness's qualifications.” Rule
16(a)(1)(G). If the government fails to comply, the court has
several options - permit discovery; grant a continuance;
“prohibit that party from introducing the undisclosed
evidence;” or “enter any other order that is just
under the circumstances.” Rule 16(d)(2).
government complied with Rule 16. Its February 9, 2019
disclosure contained Nam's curriculum vitae, a separate
written summary of Nam's qualifications, Nam's
opinions, and an explanation of how he reached his opinions.
ECF No. 382-2. Specifically, the government disclosed that
Nam obtained the cell phone records for Hahn's telephone,
and those records documented the cell towers and cell sectors
that serviced that phone. Nam explained that mapping software
was used using the latitude/longitude of the cell tower
coordinates provided by the service provider, and the
“cell sites associated with the target cell phone were
located using the mapping software and the plotted cell site
data.” Id. at PageID #8 of 15. Nam also
explained that “the call detail records and a list of
cell site locations were analyzed to illustrate an
approximate location of the target cell phone when it
initiated contact with the network.” Id.
Finally, the government's disclosure included several
historical cell site analysis maps. No. further disclosure
Federal Rule of Evidence 702
Hahn seeks to exclude Nam's expert testimony ...