Murder Trial, Part 4

11/21/08 09:06 PM Filed in: Trial
The first witness, David Walker, was sworn in at 9:08am on the fourth day of the trial. He is an AT&T Network Mobility Manager, responsible for cell site planning, switch planning, budgets, and capital investment. He was designated by AT&T to be the custodian of Dianna Gear’s cell phone records, obtained from AT&T via subpoena. As the time of a call is important evidence, it was established that AT&T rounds call time up to the next minute. The minutes start when a call is answered. Next, time synchronization between phones, towers, and switches was discussed. Everyone needs a primer on the Network Time Protocol. The district attorney noted that the time on his phone was different from that of the witness and asked why. Walker responded that a customer can manually set a phone to be ahead or behind of the network time. He did not note that synchronization of the displayed time with the network can be turned off. There was a discussion of tower locations and the RF coverage from the three “faces” on each tower. Aerial images of the cell towers were submitted into evidence.

It’s clear that the DA will use the phone records to broadly show the location of the Gear girls at the time of their calls to mom. The calls were:
  1. 5:29pm, Chelsea to mom, 3 minutes, cell id 12462
  2. 5:52pm, Chelsea to mom, 3 minutes, cell id 12462
  3. 6:07pm, Mom to Chelsea, 2 minutes, cell id 12462
  4. 6:28pm, Chelsea to mom, 2 minutes, cell id 11803 (possibly 11802 -- my notes are not clear on this point)
  5. 6:35pm ??? (the data was removed from the display before I could transcribe it)
The first four digits of the cell id identify the tower that handled the call; the last digit identifies which “face” picked up the signal. For the first three calls, the east face of the tower near the Target handled the call. I assume that the fourth call was handled by the west face of the tower servicing Bogart, GA. The witness was excused at 10:17am.

[... to be continued, hopefully tomorrow...]

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