I still think Burkett shopped them to the Kerry campaign. They would not turn down a gem such as this. So, they determine there might be problems - what to do? So, they just turn them over to CBS for them to decide if can use or not. CBS sends to the Whitehouse, ignores suspicions of experts and runs them.
Somewhere in there, CBS or the Kerry Campaign might have told Burkett they needed proof (or developed the proof themselves, took to Burkett to verify looked ok and then the documents faxed to CBS).
There isn't a doubt in my mind.