In 1947, Crisman was involved in the Maury Island incident, an early UFO hoax. Crisman's "fellow UFO witness" Harold Dahl believed the 1960s TV series, The Invaders was based on Crisman's life. Prior to this, Crisman had written to Amazing Stories magazine claiming that he battled "mysterious and evil" underground creatures to free himself from a cave in Burma during World War II.
In 1969, Crisman was subpoenaed by Jim Garrison to testify in the case against Clay Shaw in the John F. Kennedy assassination. A photocopied document later circulated among Kennedy assassination buffs claimed that Crisman was one of the "three tramps" allegedly employed by a secret government agency. During this time, he hosted a radio talk show under the pseudonym "Jon Gold" and wrote a book, The Murder of a City, Tacoma published in 1970 through Transistor Publishing Company. The book was described by reviewer Michael Sullivan as a "weird, politically slanted rant" that manages to "tie corruption in Tacoma to everything from communist infiltrators to the Kennedy assassination".
In 1979, the House Select Committee on Assassinations reported that forensic anthropologists had analyzed and compared the photographs of the "tramps" with those of Crisman, as well as with photographs of Watergate figures E. Howard Hunt, Frank Sturgis, and two other men. According to the Committee, only Crisman resembled any of the tramps; but the same Committee determined that he was not in Dealey Plaza on the day of the assassination.
Conspiracy authors consider Crisman "a nexus point for a number of conspiracies and cover-ups from the late 1940s until [his] death in 1975".
- Gulyas, Aaron John (2015). "Paranoid and Paranormal Precursors from the 1960s to the 1990s". The Paranormal and the Paranoid: Conspiratorial Science Fiction Television. Lanham, Maryland: Rowman & Littlefield. pp. 30–31. ISBN 9781442251144. Retrieved August 7, 2015.
- Peter Knight (1 January 2003). Conspiracy Theories in American History: An Encyclopedia. ABC-CLIO. pp. 690–. ISBN 978-1-57607-812-9.
- Sullivan, Michael. "On a Small Tacoma Bookshelf". HistoricTacoma.org. Historic Tacoma. Retrieved 8 August 2015.
- "I.B.". Report of the Select Committee on Assassinations of the U.S. House of Representatives. Washington, D.C.: United States Government Printing Office. 1979. pp. 91–92.