Whilst DeCoursey was keeping Tinker busy, Chadwick had opened up his tricorder and began scanning the area.
He surmised a number of things. First, the actor in question was young, so his heartbeat readings would be most likely strong. Second, he was also likely to be on the run and nervous, increasing his heart rate. So Chadwick set the scan parameters for a fast moving person with an increased heart rate. With help from Endurance, there was a good chance of tracking the fugitive.