Discussion Main / MotiveEqualsConclusiveEvidence

• Motive inverts this trope since the detectives usually don't discover the motive for the crime till the end of the episode and by that time they have a fair bit of evidence to convict the perpetrator. The show's gimmick is that we know from the start who the killer is but the reasons for the crime are hidden until the very end.
• This has been applied so many times on the CSI: Crime Scene Investigation and the Law & Order franchises (usually as a Red Herring Twist) that it would be easier to number the times it wasn't used. The suspects flying into a rage or shutting up (usually because a lawyer tells them to) when the motive is brought up (and in typical fashion of these shows, the interrogator is being rather cynical and smart-mouthed about it) doesn't helps them in any way. And sometimes, even if innocent, by the time the investigators have conclusive evidence the damage has been done.
  • A lack of an alibi doesn't help either. Motive or not, most TV cops seem to think a suspect claiming he/she was "home alone or home alone with my wife/husband/sister/brother, etc" is tantamount to a confession since there really isn't a way someone can prove that and said spouse/sibling could be lying. As well as admitting that they were anywhere near the victim shortly before their death. Nevermind that a guilty person would be far more likely to lie about something like this. One especially bad example has Benson and Stabler showing up at the home of a man who had dinner with their murder victim and proceeding to accuse him of being both her lover and her killer — with absolutely zero evidence to support either accusation.

This is a very general, and combined work, example, both of which aren't allowed by the rules. The last sentence is kind of an example, but is incomplete.