The general reliability of data from GPS monitors was insufficient to allow admission into evidence of the speed data from a model that linked a defendant to an attempted murder, Massachusetts’ high court said.
In September 2015, a Black man with long hair wearing a red shirt fired multiple shots at a moving car on a street in Boston. The driver fled. Several minutes later, a witness saw a Black man who matched the shooter’s description a few blocks away.
Davis became a suspect because he was wearing a global positioning system device as part of his federal probation. The device placed him at the corner when the shots were fired, showed how fast he was traveling, and put him near the witness. Police also found a red shirt in his room.
At trial, a witness from the GPS manufacturer Davis was wearing did. The witness gave the court a overview of how GPS devices generally work and some specifics about the ET1 model. Buck also said that although BI tested ET1 for its ability to track a wearer’s location, it never formally tested the device’s accuracy for calculating a wearer’s speed.
The prosecution didn’t lay the proper foundation for the speed data from Davis’ GPS, and it shouldn’t have been admitted, the Massachusetts Supreme Judicial Court decided. It’s not sufficient to show that GPS technology is generally reliable without making any showing pertaining to the reliability of a particular model, the court said.
The case is Commonwealth of Massachusetts v. Davis, No. SJC-13014. (May 17, 2021).