No, Leonard Peltier was not found guilty beyond the shadow of a doubt. He was found guilty beyond a reasonable doubt, the same as every one else who has ever been found guilty of anything, whether it's tax evasion or murder. I don't know anything about the case beyond the name, so I'm not saying it wasn't a righteous conviction, but enough of this bullshit that there is something in law "called beyond the shadow of a doubt."

Yes, in logical terms there are some murderers for whom there really is no doubt. Anders Breivik is the most notorious one in the last couple of years. If Norway had the death penalty, they could hang him in absolute certainty that they had the right man. Unfortunately, the law has no way of separating Breivik and ilk from the ones who later turn out to be innocent.

And no Musket, capital punishment is not and never was murder. Murder is unlawful killing. Murder is a legal term, not a moral one. Capital punishment is morally wrong, but it is not murder.