If found guilty without doubts, if he was not suffering of a moment of mental breakdown/meltdown, yes. But if circumstantial evidences prove he was not himself that was not, in term of psychiatry, fully responsible, this have to be heard.
The law of the country have to be followed.
And I was not comparing with the murder of POW, as the people he killed were not, but civilians he killed were as the French in my example of war crime. If he planned it, then did it, it is a mass murder. But, until this is prove in front of a court, he has the right to be heard.
And yes, I am against the death penalty…