Duress can't be used for murder...

Why is it in the law that the defense of duress is invalid to murder?

Consider: this man who you don’t even know accosts you on the street, and demands you kill a certain person by such and such a time (demands it of you at gunpoint), and says that if you do not do it, you and your wife and family will be killed. However, if you do as he demands, a jury will find you just as guilty as if that man never demanded it of you, and you are not allowed to claim duress as a defense (therein seemingly letting the person who threatened you get away scot-free, and practically never doing anything to him).

Correct me if I am incorrect, but isn’t that pretty much the way it works?

I don’t know exactly how the law addresses you for pulling the trigger but it does consider the person who threatened you as committing murder just as someone who hires a killer would be. No matter what you were charged with you’d have a strong diminished capacity defense except for the difficulty of convincing a jury that you couldn’t just kill the person threatening you instead of his intended victim.

I think the idea is that the life of the victim you kill is worth as much as your own, so trying to save your own hide is not a reasonable defense because the harm done is as great as the harm averted.

Again, I don’t know how the law addresses this case but what you state is not a universally accepted concept. If you and someone else are adrift in the water at sea with just one life preserver between you and he tries to prevent you from from sharing that life preserver you may kill him to save your own life if necessary. The right to preserve your own life underlies our laws. This case is slightly more complicated because you are not threatened, it is your family that is in peril, however homicide in the defense of others is a legitimate defense. It just wasn’t intended for these particular circumstances but if you can present that case to a jury you have a chance if acquittal. Adjust the circumstances to place this under maritime law and you may not be charged at all.

Both good points there! I’ve searched that online a few times before, and gotten quite a few different answers, but never one clear definite answer until now of why the law is written that way. I think you both have enlightened me in your responses.

I believe there’s also an issue of immediacy: there’s a material difference between your scenario and one where the person holding the gun demands you kill that person there in front of you right now. In your scenario you have time to get help; in an immediate scenario you do not. Immediacy is probably not the right legal term.

This doesn’t sound like a good example.
Will the life preserver be able to support both of you?
If not, presumably he’s entitled to kill you to save his own life?

He may be. You are each entitled to save your own lives. I do not know how it would work if you were willing to share. I’m not saying this applies directly to the situation in the OP either, I was responding to a post that seemed to deny the right to self preservation. The premise of the law is flawed in the OP and the situation presented is rather outlandish.

Another great point that I never thought of!

If we extend the life-preserver analogy to this case, we just find that it’s acceptable to kill the person threatening you. Which it is.

But another problem with the duress defense is that your action does not in any way prevent the threatener from killing you and/or your family. If he’s sick/twisted/evil enough to make the initial threats, then he’s also sick/twisted/evil enough to kill you anyway even if you do what he says.

But what if the threatener has a co-conspirator who is holding your daughter at gunpoint in a van who will kill her unless you kill the governor and also you are Johnny Depp?

Ignoring the rather outlandish hypotheticals & Johnny Depp, one of the points behind this law is to avoid cases in court where various members of a gang of criminals try to avoid responsibility by claiming they were acting under duress. They each claim that some other guy is the leader of the gng, and would have had them killed if they didn’t participate.

So legislators have decided that the legal system works best, and society is best served if such a ‘defense’ is disallowed. Murder is a crime, no matter why you do it. Similar to the felony Murder law, anyone who participates in a crime that results in murder can be charged with that murder.