Police analysis using cell tower triangulation


The Village of Oak Brook’s Police Department recently closed a case
involving an armed robbery at a local McDonald’s and requested the
assistance of GIS to help display some of the evidence used to convict
the suspects. Following the incident the Police Department was able to
identify and arrest 3 suspects in the robbery. In an effort to build
the best possible case, Oak Brook Detectives acquired the cell phone
records of one of the perpetrators in an effort to pinpoint him in the
area of the robbery, at the time in which it occurred. The actual phone
records were a key piece of evidence because they were able to identify
usage of the suspect’s cell phone within about a quarter mile of the
McDonald’s, both before and after the robbery took place, even though
the suspect is not from the immediate area. But the Detective wanted
more than just a spreadsheet with addresses and call times proving the
suspect was in the area, he wanted a map displaying the location of the
cell towers, the time of the phone calls, and the direction from which
the calls were made.

Using the cell phone usage information provided by the detective, the
GIS staff was able to locate and map the location of all the cell
towers the suspect used during a period of time before and after the
robbery. The next step was to use the azimuth sectors pertaining to
each call made to determine the direction in which the call was coming
from. As shown in the image, the McDonald’s that was robbed is located
almost exactly in between the two cell towers used by the suspect’s cell
phone. Additionally, the map displays that the suspect was indeed
using their cell phone near the McDonald’s both before and after the
robbery occurred. To coincide with the map displayed with this article,
a second map was produced showing the cell towers that were used while
the suspect was on their way to the Village, as well as departing to
their final destination. These maps and phone records, along with other
pieces evidence obtained by the detective were ultimately used to
convict the three suspects of armed robbery. Without using GIS to
display the information, the jury would have relied on non-graphic
spreadsheets displaying the cell phone information, which doesn’t
provide the direction in which the calls were made along with the
overall perspective of the night’s incident.