DOVER, Del. (AP) — Delaware's Supreme Court has rejected the appeal of a gang member serving life in prison for killing two men in separate incidents.

The court on Thursday rejected John Brisco's challenge to a probation officer's testimony about the accuracy of a GPS tracking device that Brisco was wearing while on probation when 53-year-old Ionnis Kostikidis was shot in Wilmington in 2013.

Brisco's attorney argued that ankle bracelet records put Brisco at a different location on the same block when Kostikidis was shot.

The justices noted that Brisco didn't challenge the accuracy of the GPS device itself, and that there was overwhelming evidence placing him in the vicinity.

Brisco was sentenced to two life terms last year for killing Kostikidis and for fatally shooting 18-year-old William Rollins Jr. two years later.