MSNBC - Iraqi diplomat gave U.S. prewar WMD details
The CIA had secret information from a top Iraqi official about the status of Saddam's weapons program and they didn't believe him. Of course they didn't believe him. He wasn't saying what they wanted to hear.
In this case, they paid him money for the information, so they must have thought the info he had would be useful, but then they didn't believe it once they got it. To me this provides an excellent example of why torture for information is completely useless, on top of being completely immoral. If they don't believe the information they pay for, why should they believe the information they torture out of people.
Think about it. If you are being tortured and you deside to talk, are you gonna tell the truth or are you gonna tell them what they want to hear? IF you tell them the truth and they don't believe you, they keep torturing you. What is the incentive to be honest?
The bottom line is, people have the tendency to accept as truth those things that back up what they already believed in the first place. What is the point in gathering more information if you are just going to discount it. Why not just act on your prejudices outright, if that's all you're willing to believe anyway?