(written from a Production point of view)
William Sargent (born 28 November 1930; age 90) is the American actor who played Dr. Leighton in the Star Trek: The Original Series first season episode "The Conscience of the King". In addition to this role, Sargent has credits in two films and about thirty television shows. Born in Berlin, Germany, he currently resides in Salt Lake City, Utah.
Besides Star Trek, Sargent guest-starred on two other Desilu-produced series, The Untouchables and Mission: Impossible. On the former, he appeared in an episode directed by Robert Butler, who previously directed Sargent on an episode of Stoney Burke with Lee Delano and Kenneth Tobey. On Mission: Impossible, Sargent appeared in an episode with John McLiam.
Sargent also appeared in two episodes of Rod Serling's classic science fiction series The Twilight Zone in 1963. That same year, he was seen in two episodes of Alfred Hitchcock Presents, and appeared in a third episode with David Opatoshu the following year. In 1967, Sargent guest-starred in two episodes of the science fiction series The Invaders: one with Bill Erwin, Jonathan Lippe, Dallas Mitchell, and Phillip Pine, and another with Whit Bissell and Andrew Prine.
In addition, Sargent had a two-episode recurring role on the situation comedy series My Three Sons in 1963, having appeared as a different character on the show the previous year. He then appeared in several episodes of The F.B.I., including two in 1966 with Stephen Brooks (who was a regular at the time) and one in 1970 with Antoinette Bower. Sargent later had a brief recurring role on Cannon, during which time he worked with Barbara Babcock, the aforementioned Bill Erwin, Fritz Weaver, and Anthony Zerbe.
A 1966 episode of 12 O'Clock High entitled "The Survivor" had Sargent working alongside Seymour Cassel and fellow TOS guest performer Jill Ireland. Sargent later appeared in two 1974 episodes of Barnaby Jones, on which Lee Meriwether was a regular; Terri Garr and Mariette Hartley also appeared in one of those episodes. Sargent's other TV credits include episodes of such programs as Combat!, Voyage to the Bottom of the Sea, Dr. Kildare, The Fugitive, Mannix (in an episode with Stanley Adams, Barry Gordon, and James Greene), and The Streets of San Francisco (working with Byron Morrow).
Sargent had an uncredited role in John Frankenheimer's 1961 drama film The Young Savages, as did Stanley Adams, Clegg Hoyt, and Bill Quinn.In 1969, Joseph Sargent (no relation) directed William Sargent in the television pilot movie for the 16-episode series entitled The Immortal. In addition, Sargent can be seen in the 1972 made-for-TV movie A Great American Tragedy with William Windom. He also had a supporting role in the 1974 independently-produced blaxploitation film The Take, along with John Chandler.
Following a 1975 episode of S.W.A.T. with George Murdock, Sargent ceased acting in either film or television. He made a brief return to the screen in the 1990s, appearing in the 1997 made-for-TV movie Not in This Town. Ed Begley, Jr. was among the lead actors in this film.