Scott Peterson should get a new trial proving he could not have committed the murders because of new scientific evidence -- so claims The Innocence Project -- but Nancy Grace says the so-called "scientific evidence" is a load of crap.

Nancy appeared on the new episode of the "2 Angry Men" podcast and addressed a new theory that would have made it impossible for Scott Peterson -- who's serving a life sentence for the murders of Laci and their unborn child, Conner -- to have committed the crime.

The Innocence Project says based on scientific technology that was not available when Peterson was tried back in 2004, fetal testing puts the date of death somewhere between December 28, 2002 and January 5, 2003.

Prosecutors put the date of death at December 24, 2002, the same day Laci went missing. Short story -- Scott was already under the police microscope by December 28th, so he couldn't have committed the murders during that new timeframe.

Nancy was not having it ... first making it clear she has experience that Harvey and Mark don't have -- childbirth. She was also indignant these new-fangled scientists felt they knew more than Laci's OB-GYN.

Nancy also talks about her new book -- "What Happened to Ellen?: An American Miscarriage of Justice" -- about the death of Ellen Greenberg, and she has a thing or 2 to say about the Menendez brothers' bid for freedom.