Cellphone technology uses radio waves that connect to a service provider via cell phone towers in order to complete a number of functions--most notably the ability to send and receive calls and texts. As a user moves from one location to another, the signal emitted from their phones is received by the most appropriate tower based on distance, terrain, and signal strength. Due to the fact that cellphones can be used to track an owner’s whereabouts via global positioning satellite data, cellphone records have become important pieces of evidence in criminal court cases over the past 16-plus years.

Paul Steffes, a professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology has been testifying on the use of cellphone records since 2000. Steffes is a specialist in radio systems engineering and radio science and has testified as an expert witness in a variety of court cases. He was the expert witness in the landmark case Pullin vs. The State (September 11, 2000) that led to the Supreme Court of Georgia ruling in favor of the admissibility of cellphone evidence.

Steffes was recently interviewed for the Undisclosed podcast about his role in the trial of Joey Watkins, a Georgia man sentenced to life in prison in July 2001 for aggravated assault, a weapons violation, misdemeanor stalking, and the felony murder of Isaac Dawkins in January 2000. Undisclosed, which investigates wrongful convictions, was contacted by the Georgia Innocence Project to take a second look at Joey Watkin’s conviction.

Listen to the episode.