Todd Gelfand was a Navy captain and doctor.
Most of Gelfand's past is unknown but during a flashback in Hiatus Part 1 (episode), it was shown that Gelfand was a doctor who had helped treat Gunnery Sergeant Leroy Jethro Gibbs when Gibbs was a Gunnery Sergeant serving in Desert Storm in 1991.
NCIS Season 3Edit
In May 2006, when Gibbs was injured in a bomb that caused him to fall into a coma, Gelfand reappeared at the Navy hospital where Gibbs was being treated and proved to be a big help in treating Gibbs, even telling NCIS Director Jennifer Shepard and Gibbs's second-in-command, Anthony DiNozzo that he had treated Gibbs in Desert Storm.
During the hospital visits, Gelfand even formed a friendship with Jenny.
As a doctor, Gelfand was trained in treating all sorts of injuries, a skill that served him well in the hospital as well as on the front lines of the United States's attacks against Iraq.