Nick Cannon KNEW something was up with stuttering "America's Got Talent" fraud Timothy Poe from the get-go -- telling TMZ, one glaring clue gave the guy away ... the night of his audition.
You've all seen the footage ... Timothy Poe put on a stuttering spectacle last week on the "AGT" stage -- claiming he developed his speech impediment from war injuries. TMZ showed you his story was holier than the Pope.
And last night in L.A., Nick told us he had a gut feeling Timothy was a fraud too -- as soon as the guy stepped off the stage -- because once the cameras were off him ... Tim stopped stuttering.
Nick's first thought was Tim was so emotional he didn't have to stutter -- but looking back, Nick said, "I think he was so caught up in the moment he FORGOT to stutter."