SAM say i hand you a syring with what i say is adrenilin and you in good faith give it to someone having an anaphalatic reaction and it is infact almioderone (stops the heart). Who is guilty of murder?
Possibly nobody. Murder requires intent to kill, or reckless indifference as to whether somebody dies. This situation is one in which SAM presumably has a reasonable belief that the syringe contains adrenalin. So, she could not be guilty of murder.
This is very different to the given scenario in which the "friend" knows full well that he will be carrying out a rape scenario. If he has not obtained consent from the "victim", then he is at least recklessly indifferent to whether consent is in fact present. This most likely means that he could be convicted of rape.
...and if the person is tricked into paticipating in a real rape...
How likely is that? "Oops, your Honour. I was tricked into raping that woman! I was too stupid to even consider the possibility that she might not be consenting. Duh! Silly me."
The responcable party is the person who knowingly tricked them.
You can't absolve yourself of responsibility for your own actions by claiming "I was only following orders". See the Nuremburg trials of Nazi war criminals, for example.