Keep them locked up. Forever. Unless and until some evidence pops up that they were wrongfully accused.
Look, my absolute opposition to death penalty is not any kind of kindness overflow, or any residual Catholic sentiment. Hell, if had to choose between DP and life in prison, shoot me right now.
This is not about them, really. This is about us.
Being a gentlewoman from Ohio, you may not quite understand it (emotionally), but I was born and raised in places much less forgiving. If I would exact my - perfectly justified, by the standards of the last two thousands years - revenge on everyone who certainly deserves it ....well--- Volga, Don, Dnieper and a number of smaller rivers in the Eastern Europe would turn red for a few weeks....
No.
This is the only possible answer: NO.
Don't get me wrong: I am a lifetime member of the NRA, all-out American patriot, tea-party-ing right-wing libertarian, etc, etc .
But on this one, there can be no compromise: Countries worth defending do not execute helpless prisoners. I believe in America that is worth defending.