I have slightly rephrased a problem found on the web (Steve Miller's page):
The police rounded up Jim, Bud and Sam yesterday, following the robbery of the local bank.
The three suspects made the following statements under intensive questioning:
• Jim: I'm innocent.
• Bud: I'm innocent.
• Sam: Bud is guilty.
If only one of these statements turns out to be true, who robbed the bank?
Communicated by G. Mejia.
Apparently, there are several solutions.