Shirou, on 9 Sep 2010, 16:20, said:
War prisoners, imprisoned without a trial...
This isn't really applicable to the question at hand, as while PoW are imprisoned, they are not imprisoned for a crime committed - in fact their very status as a PoW grants them immunity from prosecution for anything they did during the war. This isn't always followed, but aside from very rare cases, PoWs are imprisoned to prevent them from fight, not for any crime they may have committed, as during war, as a serving member of military personnel you don't actually break any laws as long as you don't do things outside of the chain of command.
Re: The siamese twins this is a legal conundrum, but it is extremely unlikely that the twins would be imprisoned for the crimes of one. However, as Golan points out, one would be imprisoned for the being an accessory to the crime itself, while the other would be charged for committing the crime. Even if the second twin had no control over what their twin was doing, they would still be an accessory, as their (shared) body was being used to perform the deed - even if you don't mean to do something illegal and yet do, you are still culpable. As to how the sentence would pan out would be another thing altogether, of course - which sentence should be carried through?
No matter how you try to swing this one, the legal system will not readily convict someone without a trial first. They may well get it wrong, but there will always be a trial.