SECRET WITNESS SAW SCOTT WITH LACI's BODY

Police now have a top-secret witness who can place Scott Peterson with his wife Laci's body shortly after her death, The ENQUIRER has learned exclusively.

The witness, a truck driver, told cops he saw Peterson and his boat near the marina where Laci's body was dumped -- at the very time he had claimed he was still at home with Laci!

The issue that goes on sale Friday reveals the chilling piece of physical evidence found in Peterson's boat, why he stocked up on survival gear shortly before his arrest -- and much more.