J.T. Esteban

J.T. Esteban was a Starfleet officer in the 23rd century, and commander of the USS Grissom (NCC-638).

In 2285, the Grissom, under Esteban's command, was assigned scientific study of the newly created Genesis Planet. Traveling aboard the Grissom were Starfleet Lieutenant Saavik, and David Marcus, one of the scientists who had developed the Genesis Device. While in orbit, however, they discovered the photon torpedo in which Spock's body had been ejected from the USS Enterprise (NCC-1701). In addition, sensors registered an animal lifeform on the surface, something previously thought to be impossible.

A cautious man, Esteban refused to allow Saavik and Marcus to beam the tube aboard, quoting the regulation "nothing shall be beamed aboard until danger of contamination has been eliminated." When they subsequently requested to beam down to the planet's surface to investigate, Esteban was wary, stating that regulations only allowed such an action if the captain felt it was safe. Esteban eventually relented, however, allowing them to beam down, but continuously kept Starfleet advised of the mission's progress. Esteban and the entire crew were later killed when the Grissom was destroyed by a Klingon Bird-of-Prey commanded by Kruge, who was attempting to obtain and exploit the Genesis technology. 

Background information
Captain Esteban was played by Phillip Richard Allen.

In the script of Star Trek III, Esteban was referred to as "late forties, a cautious Starfleet veteran."

While the creators of Star Trek III didn't leave any evidence of what Esteban's initials stand for, a non-canon source – the Star Trek: The Next Generation Officer's Manual (released for the FASA role-playing game) – lists a Decker-class destroyer, the USS Jonathan T. Esteban NCC-6005, purportedly named for this character.

The  novelization establishes that Esteban was an old friend of Admiral Kirk.