ibump 2.0:
I was going to ask why they didn’t use veritaserum on Harry to get Fudge to believe that Voldemort back, but it’s the same basic question as using the pensieve. In fact there are many times when they could have used such methods to determine the truth – e.g. Sirius’s innocence. Perhaps these methods are inadmissable in court – memories can be tampered with which presumably could outsmart a truth potion as well.