Until convicted in a fair and just trial, he is not a "proven" terrorist. And how fair and just is a trial that relies on evidence extracted with torture? In WW2 the US relied on interrogation of captured German soldiers conducted by recent immigrants and refugees from Germany. Generally,  a cigarette, shared family photos, and empathy were all it took. Trickery was sometimes used, such as setting up a tent staffed with a supposed Soviet intelligence officer. Since the Germans were petrified of being turned over to the Russians, the casual threat that they had been flagged to be turned over for some reason was all it took. Torture was never used. And when the Bush regime resorted to torture the association of these specialized veterans objected. Its likely that the question of whether evidence tainted by torture can be used will eventually reach the Supreme Court. If the Court follows long standing US and international law, it will say no.