Here's one a friend of mine read in Dear Abby, about a stupid criminal:
Police in Penn. interrogated a suspect by placing a kitchen colander on his head and connecting it with wires to a Xerox machine. A piece of paper with the words "He's lying," was placed in the copier. After the suspect responded to each question, the officers would press the "copy" button, and the words,"He's lying," would print out. The suspect figured the "lie detector" had the goods on him, so he confessed.