Cell Tower Junk Science

Article excerpt

Despite claims to the contrary, cell phone tower evidence cannot reliably place a suspect near a crime scene

FCC rules dating back to the late 1990's require wireless carriers to identify a 911 caller's location within one-fifth of a mile. Wireless carriers comply by simultaneously using three or more cell towers or GPS satellites to calculate the callers' latitude and longitude. Inexplicably, at many criminal trials the prosecution uses a different approach based only on one or more call detail records supplied by the wireless carrier. This inferior method can only be used to establish the caller was within a 25 radius of the cell tower specified in each call detail record.

Investigators frequently use cell phone tower information in an attempt to place a suspect near a crime scene, and for years prosecutors have successfully convinced jurors that the data from a single cell phone tower can reliably specify a person's location at the time of a call. But in reality it takes GPS tracking or simultaneous ping information from at least three different locations to locate or track a caller and to determine his or her latitude and longitude. Prosecution experts acknowledge that the use of accounting department call detail records cannot precisely determine a caller's location, since the caller need not be immediately adjacent to the cell tower, but they suggest that the accounting data proves that the caller was within a mile - or five miles - or ten miles - of the tower. The problem is that their underlying claim is false even when it is combined with the following information:

* Cell tower latitude and longitude and street address;

* Telephone company drive test maps that validate cell phone reception within the intended coverage areas;

* Maps showing radio frequency [RF) coverage for each cell tower;

* PowerPoint® representation of defendant's travels based on serial multiple tower tracking; and

* Antenna information.

The Federal Communications Commission understands the relevant science. That is one of the reasons why they have mandated that wireless carriers provide Emergency 911 location information by one of two methods:1 handsetbased, where location information is generated by GPS or similar technology installed in the caller's handset, or network-based, where location information is generated by analyzing the caller's wireless signal in relation to nearby cell sites in the carrier's network. The FCC's rules require wireless carriers to identify the caller's location for a specified percentage of 911 calls within a range of 50 to 150 meters for carriers that use handset-based GPS technology, and 100 to 300 meters for carriers that use network-based technology. No one who understands the relevant science would ever claim that data from a single cell phone tower is adequate. The following cases illustrate the limitations of cell phone tower evidence.

Case 1

by Nicole Hardin, Ocala public defender, and Manfred Schenk, expert witness

State v. Adrian Brown was a murder case with an eyewitness and cell phone tower evidence. The evidence seemed overwhelming. And it was not only overwhelming, it seemed damning, placing the defendant in the area right after the murder and tracking him from Ocala to Miami in the hours following the murder.

The Assistant State Attorney listed a "network engineer" affiliated with Sprint the day of jury selection and the judge refused to exclude him. The State Attorney called the Sprint phone worker as their last witness. He gave a power point presentation, and the State's rebuttal closing argument relied almost exclusively on how the "pings" of the defendant's cell phone had proved their case. The Assistant State Attorney actually walked around the courtroom saying "ping, ping, ping" and tracking the phone in evidence to the defense table. However, the trial ended in a hung jury.

In the retrial the defense focused heavily on winning big concessions on cross from the engineer. …