Mitchell was the last person to be executed in California before the Supreme Court of California ruled in 1972 that the death penalty was unconstitutional (the Supreme Court of the United States made a similar ruling later that year). Mitchell was the 194th person to be executed by gassing in California (1937-1967), and the only person to be executed in that state during the term of Governor Ronald Reagan (1967–1975). Both Reagan and his predecessor had declined clemency. Mitchell's case had been heard twice by the US Supreme Court and twice by the California Supreme Court.
After Mitchell, there were no more executions in California until 1992, when Robert Alton Harris was gassed. (The gas chamber was ruled unconstitutional in California in 1994.)