Jim Markham was a Ballistic lab tech at the Miami-Dade Crime Lab. Markham became the head of the ballistics section when Calleigh left after John Hagan committed suicide there, but unfortunately, Markham made regular mistakes such as leaving skin cells unexamined on a bullet casing.
Calleigh later grew tired of Markham screwing up and returned to the Ballistics lab which also resulted in Markham being transferred elsewhere.
He was played by Joshua Leonard.