The problem all comes back to the famed Nazi defense summarized as, I didn't know. I was just following the rules. And believe it or not, this has throughout history been one of the most effective defense strategies for the perpetrators of all manner of cruelty and crimes against others. Sadly these purveyors of misery trampling all over the rights of others will likely not be prosecuted ever.
But this still will open the gate. Let the poison pusher go free, as long as it is on the record that he administered the poison.
I'm not a lawyer .... I just cannot believe there is no strategy of this type... and someone who does know can think this through better.