Over the last half-century, the widespread use of global positioning systems (GPS) technology has supplemented the toolkits used by law enforcement and prosecutors for investigating and prosecuting crimes. Although GPS technology is widespread and generally accepted as accurate for most location monitoring applications, the use of the technology by prosecutors as evidence in criminal trials may not always be permitted. The Massachusetts Supreme Judicial Court recently reversed a lower appellate decision that had allowed the Commonwealth to introduce GPS evidence to prove a defendant’s speed and location around the scene of a crime.
In the recently decided appeal, the defendant was accused of armed assault with intent to murder after he allegedly fired a gun into a moving car in an incident in September of 2015. Although there were no direct eyewitnesses to the crime, witnesses described a man meeting the description of the defendant in the area of the crime shortly before the shooting and also fleeing after. Because the defendant was on federal probation for a previously committed crime, he was wearing an ankle-mounted GPS monitor at the time of the crime. Law enforcement investigators assessed the GPS monitor data to determine the defendant’s location and his speed of movement around the time that the crime was committed, and he was arrested for the shooting.
The defendant was charged with armed assault with intent to murder. At trial, the prosecution successfully admitted the evidence from the GPS monitor in the case against him against defense objections. The defendant was convicted of the charges and ultimately appealed the evidentiary rulings and his conviction to the Massachusetts Supreme Judicial Court. The defense argued that the GPS data pertaining to the defendant’s location and speed at the time of the offense was not sufficiently reliable to be admitted at trial. The high court agreed with the defense in part, ruling that the GPS data from the particular model of ankle monitor the defendant was wearing had not been properly proven or formally tested to accurately measure the speed of someone wearing the unit. The high court rejected the defense’s argument that the location data was not reliable, as it had been formally tested and was generally accepted as accurate in the legal and scientific communities. After determining that the evidence of the defendant’s speed was not admissible, the court reversed the defendant’s assault conviction, and the prosecution will need to seek a retrial of the defendant if they desire a conviction.