Well, I say that they should in the case of sleepwalking, as that is simply their subconscious acting out something that their conscious mind had considered, but would be unable to achieve due to certain consequences.
Loss of awareness during the time the act was committed, you could plead insanity to your case. However, don't think that this would get you off the hook. First, they would have to find connections if you WERE actually insane when you committed the act. Next, you will have to be stationary until you are well again. Finally, after you are "cured", you will be sent back to court to stand trial for that action again and will most likely be deemed liable for that said action. Pleading insanity is a loss/loss situation.
Despite someone inducing you with these drugs to make you unaware of your actions, he/she cannot be liable, since he/she would not have known that you would have committed an act.
If one is truly sleepwalking, they should not be charged with crimes because they were in a state of temperament insanity of which they had no control over. Though I think that shouldn't let them off the hook entirely.
The issue of crimes committed while sleepwalking is a controversial one.
As knight stated if they are sleepwalking then they can't control their actions. So they shouldn't be held responsible. However, if they are self-induced or intoxicated, they should be held responsible.
Even when sleepwalking the actions are those of your conscious mind. Your sub conscious gets ideas from your conscious but it doesn't have the limitations.
