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Study: Cellphone location data is not necessarily accurate

In 2009, the National Academy of Sciences issued a blockbuster report on the state of the science in forensic investigation. That report concluded that, "with the exception of nuclear DNA analysis ... no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source."

On this blog, we've discussed the fact that many common forensic techniques are not supported by science. That includes techniques that prosecutors and police have long relied on, such as drug field tests, bite mark comparison, blood spatter analysis, image comparison, microscopic hair comparison, ballistics, lie detector tests and more.

When the prosecution or the defense seeks to introduce scientific or technical evidence, the U.S. Supreme Court has said that one factor to consider is whether the technique is widely accepted in its field. Yet far too often, this type of evidence is admitted by judges without serious review of how reliable it is.

Does your cellphone company know exactly where you've been?

New research suggests that Cell-Site Location Information (CSLI) is far from infallible when it comes to proving the specific location of a particular person at a given time. Nevertheless, CSLI data is widely admitted in criminal prosecutions. Indeed, the Supreme Court has ruled that law enforcement needs a warrant in order to obtain CSLI from phone carriers.

The idea behind CSLI is that, even when your location services setting is off, your cellphone pings the nearest cell tower, or "mast," when you use the phone nearby. As you travel around, the cell tower your phone is pinging changes. This allows the system to map where you have been. A map of your activities can then be created by software.

The Guardian reported that the software that creates the maps has some major bugs. For example, sometimes the system fails to ping the nearest cell tower, or at least fails to record it. This allows an incomplete map to be created and, possibly, used as evidence of a defendant's whereabouts.

Moreover, the system sometimes links phones to the wrong masts, records incorrect locations for text messages or even uses the wrong location for a given cell tower. In some cases, the system claims that a phone simultaneously pinged several towers at once, sometimes miles apart.

In the U.S., a Kansas couple is suing a company that creates CSLI maps for police. A glitch in that company's software made the couple's rural home the default location for CSLI. That sent police to their home repeatedly whenever the default result showed up on their CSLI maps of a suspect's activities.

CSLI simply may not be reliable enough to be admissible as evidence.

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