A Black man with long hair and wearing a red or pink shirt or sweatshirt fired multiple shots at the driver's side window of a moving blue sedan. The driver of the sedan fled and did not testify at trial. A civilian witness, Ilene Rock, testified at trial about seeing a Black man with braids and a red shirt running away from the location of the shooting. D became a suspect after police made an inquiry whether anyone wearing a global positioning system (GPS) device at the relevant time was in the vicinity of the shooting. D was on probation for a Federal drug charge. D was wearing a GPS ankle monitor called an “ExactuTrack 1” (ET1) manufactured by BI. D's GPS device showed he was at the location where the shooting took place very close in time to the shooting, and his speed matched the shooter's movements, according to surveillance footage and testimony from the civilian witness. GPS tracked D from the crime scene to his home. Sergeant Thomas Carty also obtained a video from a video camera affixed to residential property. The video is not high enough resolution and is taken from too far away to discern any features of the shooter's face. Officers executed a search warrant at D's home. They found a red long-sleeved crew neck sweatshirt under a pile of clothes in D's bedroom. The sweatshirt tested negative for gunshot primer residue. Before the GPS evidence was introduced at trial, the judge conducted a voir dire of P's expert, James Buck, manager of product development at BI. Buck opined as to how GPS worked and the device gathered both location and speed data. To triangulate a device's location, it must receive signals from a minimum of three satellites. To determine a device's speed and direction, it must receive signals from at least four satellites. ET1 records the wearer's location and speed once per minute. The device takes a sample every fifteen seconds and then selects the best sample of the four to log. Buck stated that BI had conducted formal testing of the ET1's ability to measure location, but its ability to measure speed had never been formally tested. The testimony was admitted. D was convicted of armed assault with intent to murder and appealed.

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