There's an entire series of amusing books, published in the USA, devoted to the adventures of the less clever members of the criminal class, entitled "More Stupid Criminals."
From one of them: Bank robber writes his "gimme the money or I'll shoot" note on the back of his appointment card for his next visit with his parole officer.
Court cases involving sub-Einsteinian crooks: Detroit, Michigan. Detectives put a collander, i.e., a plastic vegetable strainer on the arrestee's head, connected it with a piece of wire to the photocopy machine. They placed in the machine a note that said "he's lying." Every time the arrestee gave an implausible answer, they pushed the copy button. And told the yegg that the machine had caught him out.
The arrestee, convinced that his powers of deception were no match for modern science, confessed. He was prosecuted, but the complaint was quashed on the basis that a confession, extracted through the use of a sham "lie detector" was involuntary and inadmissible under the 4th Amendment of the US Constitution.
Nebraska. Crook, suspected in meat packing house break-in, was found in possession of a supply of individually wrapped components of cows for which (as far as I am aware) there is no use, i.e., rectums.
The arresting officers ridiculed the arrestee and suggested that he was too stupid to be involved in crime.
The arrestee responded "If I have to go to jail for stealing a bunch of cow's assholes, I'm going to be annoyed," or words to that effect.
The prosecution offered these remarks as an extra-judicial confession. The case went up to the Court of Appeals to resolve the question of whether a confession obtained by laughing at the defendant is inadmissible.
From Mike Royko's column in the Chicago Sun: Foundry worker, late Saturday night, arrested for public intoxication and resisting arrest.
He told the arresting officer: "When we have revolution, we shoot all you red-nosed Irish bastards by wall."
Back at the precinct station, one of officers put on a judge's black robe. They removed the defendant from his cell, summarily "tried" him for "high treason," told him that the sentence was death, and took him back to his cell.
Then, as they were leading the now bewildered drunk to the "gallows," still another officer burst in to announce that the defendant's sentence had been commuted by the state governor.
The next morning, this defendant was presented for arraignment. There, he began babbling to the magistrate some fantastic-sounding gibberish about "high treason" and that he'd been "pardoned by the governor.""
The magistrate, leaping to an obvious, but erroneous, conclusion, ordered the defendant's confinement, for thirty days, at a psychiatric hospital, for the purpose of determining whether he should be civily committed.