Not just concrete evidence. There is no evidence for any of that. The bush administration admitted that. That is what happens when prisoners are tortured for information. They lie. And what happens when americans pay ransom for prisoners. The northern alliance is paid for some people they capture. How many did they get rid for their own reasons?
Are you claiming that this guy was innocent and was framed by the Northern Alliance? If so, what was he doing in Afghanistan? He is originally from Saudi Arabia and later received the British passport. He had no family/work connections to Afghanistan, and at that time even schoolchildren knew that traveling to that country was risky.