Plea Bargains?

So we can still get information out of the Christmas bomber because we have the possibility of doing a plea bargain? That means that we will lighten his sentence in exchange for information in spite of having now all the evidence we could possibly need for a conviction on the charge of trying to murder 300 people. So we are now going to let a foreign intended terrorist murderer out early in order to get information that might lead to finding more intended terrorist murderers? Isn't there something odd about that? Would we let Reid out earlier if he had some information? KSM? Bin Laden? Does anyone else find this odd?