Dr. Phil: Casey Anthony's Parents Spill DEATH SECRET On My Show!!

Casey Anthony's parents are finally opening up about what REALLY happened to their granddaughter -- revealing NEW information that could have changed the outcome of the case ... at least that's what Dr. Phil wants you to believe.

The good doc has released his first promo for his tell-all interview with George and Cindy Anthony -- and though neither one of them utters a word during the 30 second spot ... Phil seems pretty excited about some new "information" that he claims America has never heard before.

During the interview -- set to air on Sept. 12 -- Phil asks, "You know the truth, don't you?"