(written from a Production point of view)
Michael John Pollack, Jr. (30 May 1939 – 20 November 2019; age 80), better known as Michael J. Pollard and also affectionately referred to as "Spud Pollard", was the actor who played Jahn in the Star Trek: The Original Series first season episode "Miri".
Michael Pollard was born and grew up in New Jersey, the son of Michael John Pollack who worked as a bartender and his wife Sonia. Pollard himself was married twice, first to actress Beth Howland, with whom he had one daughter Holly Howland, and a second marriage to Annie Tolstoy with whom Michael fathered a son Axel Emmett Pollard. Both of Pollard's marriages ended in divorce, the first in 1969 and the second in 1976. Pollard never remarried after the divorce of his second wife.
By the mid-1970s, Pollard was suffering from severe drug and alcohol abuse. He received treatment in the 1980s and afterwards become heavily involved in support group treatments and sponsoring other recovering addicts and alcoholics. Rumors persisted into the 1990s that Pollard was still suffering from addiction, mainly due to odd behaviors during interviews, such as staring into space when speaking or rambling answers to questions. 
Pollard was in acting since 1958. A character actor, he accumulated almost a hundred appearances in movies and television series since then. Most of his training was acquired through the Actor's Studio in New York City, where at one point he shared the stage with George C. Scott and attended acting classes with Marilyn Monroe.
In 1967, Pollard earned an Academy Award nomination as Best Actor in a Supporting Role for his role of C.W. Moss in the film Bonnie and Clyde. He also earned two Golden Globe nominations for that role, one for Best Supporting Actor and one for Most Promising Newcomer. In addition, his performance in Bonnie and Clyde won Pollard a BAFTA Award as Most Promising Newcomer to Leading Film Roles.
Also in 1967 he and Angelique Pettyjohn appeared together in an episode of The Girl from U.N.C.L.E. ("The U.N.C.L.E. Samurai Affair").
Michael Pollard died from cardiac arrest on November 20, 2019. 
Appearance in Star Trek
Pollard's character in "Miri" was scripted to be between fourteen and fifteen years of age, yet Pollard himself was twenty seven years old at the time, only a few years younger than the main characters in the episode, and about the same age as the actors portraying security guards. Despite such a vast difference in age, Pollard's "baby-faced" looks had earned him the role. Pollard had previously been considered for the role of Charles Evans in "Charlie X". (These Are the Voyages: TOS Season One, p. 196)
- The Russians are Coming, The Russians are Coming (1966, with Brian Keith, Andrea Dromm, Theodore Bikel, and Don Keefer)
- Lost in Space episode "The Magic Mirror" (1966)
- Roxanne (1987, with Steve Martin)
- Scrooged (1988, with Alfre Woodard and John Glover)
- Tango & Cash (1989, with Marc Alaimo, Roy Brocksmith, Teri Hatcher, Clint Howard, Glenn Morshower, and Phil Rubenstein)
- Superboy episodes titled "Meet Mr. Mxyzptlk" and "Mr. and Mrs. Superboy" (1989, with Sherman Howard)
- Split Second (1992, with Kim Cattrall)
- The Odyssey (1997 TV movie, with Vanessa Williams)
- Merchants of Venus (aka A Dirty Little Business) (1998, with Robert Easton, Charles Dierkop, and Helen Cates)
- House of 1,000 Corpses (2003, with Sid Haig, Rainn Wilson, and Tom Towles)