It can't legally be used against him, but unless you find a slate of jurors who have been living under a rock for years, they'll all know about it and it will weigh in their decision. Also, people aren't going to give a fuck that a guy who is behind the deaths of thousands of people was subjected the torture.
New York's death penalty is irrelevant. The charges are being brought in federal court, and there is a federal death penalty (lethal injection).
Replying to bold.
This is not about the people. If terrorists were given civil trial, then rule of law should be followed. Thats why people like me have a problem with that, since terrorists have no civil rights. NY already being a "target" will become more of a "target", Since they did not receive a speedy trial , much of the evidence could be thrown out. They are not US citizens and do not deserve the same rights we have. With "rule of law", there is a chance of an aquital. We have a process to handle such combatants. It's not Federal Court in Manhattan.
I was wrong about death penalty, since I overlooked that trial will be on Federal Court.