At least with Biden you could easily tell when he was lying to you.
Of course with Obama it now seems that EVERYTHING was a lie so I guess it's now easy with him as well. You know the whole "if his lips are moving" thing ...
or whenever he says:
"Let me make one thing perfectly clear" (it won't be clear and he will be lying)
"As I have always said" (Usually it was exactly the opposite)
"As I said before" (Usually he's never said it before)