Who am I? Who are you? We are nothing but the sum of reactions occurring before us (or after us, or right at this moment, as technically we can't rule out retrocausality). Hence determinism means everything you do you are completely responsible for, since "you" can only rationally be taken to mean everything that lead up to and caused your present behavior.
Satan wants to punish everyone!... He always tries to fill their hearts with evil desires. It is satan that puts evil thoughts into a person's mind for them to then act upon it. Though you can't really blame the devil because that person who committed the sin can control wether they act upon the thought or not. The devil just puts the thoughts in people's minds.
The worst that can be said is that you dabble with the devil, there is a price to pay. Demons do not literally take control of you and force you to kill or harm, etc. There is a agency of choice in allowing such a creature, one who has no real power over you, to come into your 'life' as it is. They play upon the desires you leave out there for them, and there is little if any compulsion about a demon.
Because God is there, demons have no power over man kind. You can only commune with and be influenced by a demon if you so choose to.
And they will exact their price.
Firstly, they either would be considered as the demon or possibly using Demon Possession as an Excuse, as it would be impossible to prove demon possession, thus could consider it an excuse.
Secondly: It would be also their fault for not resisting the pressure put on them by the demon, thus considered as weak and likely to commit such an offense again if not incarcerated.
So either way, Jail is the best result, or if they repeat offend, execution! :-D~
If we assume that a demon has caused someone to do something wrong, then there is no rational reason to punish this person as humans. Additionally, god is unable to punish this person as it was the demons fault and not the person. If we assume the person can do crime without demons, then we are left with the fact that demons don't exist. Surely, also then god does not exist? Then no longer do theists have a get out of jail free card to play.
Okay, assuming that there is a deity--which is more than likely the Christian god, as religious person in the United States might assume-- this deity would not,once again, assuming that it is benevolent, punish people via demons. I think it would be much more likely that the deity would provide opportunities for the wayward to correct themselves. With that being said, I also feel that if someone is deviant enough for them to warrant punishment, then there will be punishment resulting from their actions in this world, this reality--without the meddling of a supernatural entity.
However, this is all too similar to arguing over the number of angels on the head of a pin, or however the medieval argument goes.
However, there's no way to know for sure. The most anyone could claim in a logical, possible scenario is "temporary insanity" or the like.
For that matter, if the person was actually possessed... There should be some sort of restraints placed, in case the possession ever occurs again.