Nick and Razor, I think you're both right in the vast majority of cases. People need to be responsible for their own actions, and, as I told my eldest son after he hit his younger brother, just because someone does something to you, that doesn't mean you should do something back. There are too many problems today because people don't take responsibility for their actions.
HOWEVER, the question used the word "ever" and I feel that there is a small minority of cases where, yes, a person can be culpable for another's actions. In a much larger set of cases, they can be an influence in another's actions, but the majority of responsibility lies with the person who acted, and that is where I agree with Razor and Nick.
Razor -- you were looking for a realistic scenario where someone else controlled a person. Would you consider the drugging a person with a hallucinogenic drug such a case? I'm not talking about where someone has taken such a drug voluntarily, but the case where a person gave it to them without their knowledge. I can't see how the victim in this case can be responsible for their own actions.