One potential Black Dahlia suspect was Bugsy Siegel, though it may have just been wishful thinking on the part of the LAPD. Bugsy was not known to socialize in the same circles as Beth Short and he was not known to be so sadistic as to inflict the type of horrific injuries visited upon Ms. Short.
He was apparently cleared, though the 'suspicions' were probably a sham ginned up by the LAPD to come up with an excuse to look into his business dealings.