Columbo (1971)

A Deadly State of Mind - S4-E6

Stupidity: Collier damages a post with his car as he leaves the driveway. His car would certainly have been damaged. The storyline is not long enough for Collier to have his car repaired. Columbo knows about the damaged post, but he never looks into how the damage occurred and never looks at Collier's car, which would have been incriminating.

Leicaman

Troubled Waters - S4-E4

Stupidity: After Danziger fires the revolver into the mattress, Columbo compares that slug with the murder slug. He puts them both on a narrow railing. It is noticeably windy, and ships often roll with waves. Columbo would not risk losing both pieces of evidence.

Leicaman

Troubled Waters - S4-E4

Stupidity: The cruise ship is sailing from LA to Mazatlan in Mexico. Looking at a map, the ship will hug the west coast on its journey therefore is never far away from land. The murder takes place on the first evening of the cruise only a few hours after setting sail by which time they won't be far from San Diego. Why didn't the captain order the ship into San Diego or another suitable harbour and let the police take over the investigation?

A Deadly State of Mind - S4-E6

Stupidity: In the final scene: Columbo lays a trap for the murderer (George Hamilton). The 'eyewitness' when Hamilton fled the murder scene was a blind man. Hamilton is aware of this. Columbo's gambit depends on Hamilton's assumption that Columbo has coached the witness to act as though he was sighted so as to convince Hamilton that there is evidence against him. In fact, Columbo has the witness' brother, who is sighted, pretend to be the eyewitness and identify Hamilton as the man he saw driving away. When Hamilton falls for Columbo's trap and, believing he is in the presence of the blind man, tries and fails to 'prove' the man can't see. By doing so he reveals his knowledge that the witness was blind, incriminating himself. The problem is, that only a minute or so previously, Columbo had placed Hamilton under arrest, and failed to read him his Miranda Rights. Considering that Hamilton's slip up is the ONLY evidence Columbo has against Hamilton, this was a spectacularly stupid move on Columbo's part. Regardless of how many officers were present to witness this, the fact is that Hamilton was under arrest and had not been advised of his right against self-incrimination; meaning nothing that he said when under arrest can be used against him.