Lieutenant Evans was a 23rd century Starfleet security officer aboard the USS Enterprise serving under Captain James T. Kirk.
In 2268, Evans reported a disturbance in crew quarters to Kirk, and discovered to find Troyian Ambassador Petri had been stabbed by the Elasian Dohlman, Elaan.
Evans later discovered Kryton conducting sabotage in the engineering room of the Enterprise. Kryton attacked Evans and stole his phaser, which he used to kill himself. (TOS: "Elaan of Troyius")