Leopold and Loeb, a 1920s 'Crime of the Century', featured Clarence Darrow
and the introduction of 'mental illness' as a defense instead of insanity. The
two murdering defendants were from wealthy families and killed a boy on a
lark. They both went to prison, where one was killed, and the other got out
after 33 years incarceration. The Columbo episode looks to have been based
on this case.