He appeared in several films written and/or directed by Ed Wood.
Farrell played the role of underworld figure Umberto Scalli in three films- The Devil's Sleep (1949), Racket Girls (1951), and Dance Hall Racket (1953). Scalli appeared in Dance Hall Racket despite being apparently killed in Racket Girls. He had previously played a character called "Dr. Wright" in two separate films as well (both directed by W. Merle Connell).
In addition to his work as an actor, Farrell also had a career in law enforcement, which was later tainted by scandal.