The Maryland Court of Special Appeals has rejected evidence in a murder case based on quasi-cell site location info, according to Tech Dirt.
The “drive test evidence,” utilizing cell towers, doesn’t link the defendant, Bashunn Phillips, to anything. In a motion, filed in August 2015, Phillips sought to exclude the “RF signal propagation map and related testimony.” This form of evidence can be obtained without a warrant in Maryland and historical cell site location data is still a third-party record as far as the federal courts are concerned.
In this case, local law enforcement had the FBI perform a “drive test” of cell towers in the criminal activity area ten months after the incident. According to Afentis Forensics, a company that bills itself as “Cell Site Analysis Experts,” this method of “Cell Site Analysis (CSA) is the science of reconstructing the physical movements of a mobile telephone or telecommunication device” that “can be especially powerful in attributing contact between individuals, proximity to a scene of crime, patterns of movement of suspects, and testing the strength of alibi evidence.”
How accurate is this data? That’s a question that’s still up-in-the-air. According to a company that offers cell site forensics, “a number of factors come into play, including the type of signaling technology used (GSM/UMTS/CDMA), the local topology (man-made or natural obstructions), the height of the antennae, type of CDRs available, physical location of other masts, angling of the transceivers, and degree of network activity (other subscribers). In some instances, Cell Site Analysis can be accurate to a few meters, or sometimes a few streets (approximately a postcode).”
This type of technology was originally intended to inform service providers of possible dead zones. Narrowing down a historical cell signal after the fact via an RF analysis is risky and this data is not generally accepted in criminal investigations. William Folson, accepted as an expert witness “in the field of cellular technology and historical cell site analysis,” explained that he “consider[s] [drive tests] a waste of time” because “[t]hey add no value to the historical analysis of a cell phone.” He also noted that “a drive test is not representative of the strength of the RF signals on any other date. Additionally, he pointed out that “drive tests were not peer reviewed, accepted by the scientific community, or used in criminal investigations.”
Also noted in the testimony from the case, the coverage area of a cell phone tower should not be part of a court case “unless that information comes directly from the wireless telephone company in the form of a radio propagation map.”
July 25, 2017
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