Location data obtained from cell towers is coming up in more criminal cases, but it is often misunderstood.
Almost twelve years ago, a Portland woman was accused of a murder. She said she did not do it and spent two years in custody waiting for her day in court. Right before the trial, prosecutors approached her with cell-tower data they claimed placed her near the scene. She still professed innocence, but reluctantly took a plea to a lesser manslaughter charge. The judge sentenced her to serve 15 years.
New lawyers and phone experts reviewed the evidence and found flaws in the prosecution’s evidence. One tower with a 360-degree antenna and a 300-mile range could not “pinpoint” a cellphones location as had been claimed.
Tower data is able to place a cellphone in a broad area, but cannot pinpoint the phone’s location. The only way to get an exact location is through three-tower “triangulation.” However, this evidence is not stored and thus cannot provide detailed location information.
Last April, in an unusual move a U.S. District Court Judge tossed out the woman’s guilty plea holding that expert testimony on “the reliability of cell-tower evidence to pinpoint a caller’s location, likely would have changed the outcome of the trial.” The prosecutor will not retry her. She served 12 years following the wrongful conviction, because the initial attorneys did not understand the cell-tower evidence.
Expansion of use and limitations of cell-tower data
The Economist reported that last year AT&T alone received 37,839 court orders, subpoenas and search warrants looking for tower location data. This year, the number has likely already been surpassed, because 30,886 requests had been received by June, according to the company.
Prosecutors increasingly use the evidence to place a suspect at the location of a robbery or assault. The forensics chief for the public defender’s office in Los Angeles County said cell-tower information comes up in every major case describing it “like fingerprints, it’s that common.”
Forensic experts find prosecutors do not understand how the technology works. A prosecutor might claim a phone connected to the nearest cell tower, however depending on the conditions two calls from the same location could be routed through different towers. Tower ranges overlap and computerized switching centers route calls based on many factors including foliage, nearby cars, weather, time of day and the function of the phone itself. The algorithm that wireless carriers use for routing calls is a trade secret thus the companies do not always answer questions about how networks operate.
The evidence from towers may have a place when the claim is that an individual moved between broad areas. For example, if the claim is that the individual drove from Salt Lake City to Chicago.
When charged with a crime, immediately contact an experienced criminal defense attorney. It is important to seek someone who specializes in criminal law and is up-to-date on technology and how to challenge faulty evidence.