Leslie was a human Starfleet officer who served during the 23rd century. In the 2260s, Lieutenant Leslie served in the operations division aboard the USS Enterprise. Leslie was cross-trained to perform a variety of duties aboard the Enterprise from helm and navigation duties, to security and engineering.
In 2265 Lieutenant Leslie was assigned to the USS Enterprise at the request of Captain Kirk, who was impressed with Leslie's record in navigational sciences, which led to him being assigned as a relief navigator and helmsman. His advanced skills in navigation also allowed Leslie to take on a second career as a security officer.
Leslie continued to serve aboard the Enterprise well into the 2270s. In 2277, Leslie (still holding the rank of lieutenant) was serving as the ship's A & A officer.
By the mid-2280s, Lieutenant Commander Leslie had been assigned to the USS Lexington.
In 2293, Leslie attended James T. Kirk's memorial service in the grounds of Starfleet Academy, along with many other former Enterprise crewmembers.