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Did the cell phone cause the accident?

In the Cameron County Texas case of Ramiro Terrones Silva vs Gabriel Dwayne Davis, the driver, Mr. Davis caused an accident in Port Isabel, Texas. He was accused of causing the accident due to being distracted by his cell phone. Cell phone network data was provided by AT&T consisting of reports containing cell tower locations, phone calls, text messages and data activity. The locations of the cell towers connected to the phone were mapped onto Google Earth as shown below. The blue icons represent the location of the cell towers connected to the phone at the time, not the position of the phone.

Davis drove south down I-69E then east on Hwy 100 handing off to different cell towers as he travelled. According to the police report the accident occurred at 3:59pm. The cell tower location near the accident location was logged at 4:18 pm as shown on the right side of the map. The location point prior to 4:18 pm was at 3:50 pm so the cell phone data confirms the accident occurred between these two times.

As stated prior, there were no voice calls or text messages in the time window prior to the accident. There were, however, data activity records. Data activity consists of any application on the phone that sends data back and forth through the cellular network on to the internet. Typical applications that send and receive data might be a web browser, social media, mapping, music, etc.

There were two data records that were logged by AT&T within the time frame of the accident.

The two data records in the AT&T file looked like the following table.

ET is the elapsed time of the session, in this case equal to one hour or 60 minutes. Bytes up is the amount of data that was sent from the mobile and Bytes Down is the amount of data received by the mobile over the 60-minute time-period. The data rate is simply the number of Bytes divided by the time.

If we add the Bytes Up and Down in the first record we get (1,467,448 + 7,376,366) 8,843,814 Bytes or 8.84 Megabytes or simply 8.84MB transmitted over a 60-minute time-period.

I compared that to data transfers for typical mobile applications. There are over 3 million apps in the Apple store and it is impossible to compare them all so I picked the ones most used. These included video, music, mapping, and social media apps.

The data rate on the phone compares to normal Spotify use and low Google Music rates as shown in the highlighted table below. Two columns of values are shown, one for data transferred in 12 minutes and one column for data transferred over an hour. The 60-minute AT&T record begins at 3:37 pm which is 12 minutes prior to the reported time of the accident at 3:59 pm. The first column is the typical amount of data transferred in 12 minutes and the second over an hour. If the app on the phone stopped at the time of the accident then the entire 8.84MB would have been transferred in the first 12 minutes of the 60-minute period.


The table below shows the typical data rates for Apple and Google Mapping apps. The highlighted values were consistent with the data rates on Davis’s phone.

Video uses much more data than what this driver used so that was ruled out. Social media was also ruled out as it typically uses much more data than this driver used. Since Music and mapping apps are mostly non-user interactive there was no way to prove the user was interacting with the phone by analyzing the data records. Ultimately this case was settled for a nominal amount.

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