A Deadly State of Mind - S4-E6
Trivia: Unusually enough for a television show devoted to a homicide detective and the way he unravels the plans of cunning murderers, the fact is that Columbo has nothing to do in this episode. Doctor Collier is seriously assaulted by Carl Donner who then goes on to violently attack his wife. Use of deadly force to prevent such an attack is allowed in the United States. Collier does not commit murder; he doesn't even commit a crime. You'd think such a hightly educated man would know enough to keep his head, call the police and explain what had happened. He wouldn't even be charged.
Trivia: The show featured the first toilet flush heard on TV.
Trivia: The stiff-necked, humorless Sheriff Tankersley was a nose-thumbing parody of a real (and really unpopular) person. William Tankersley was a notoriously prissy network censor who was infamous at the time for trying (unsuccessfully) to stifle the naughty bits on All in the Family.