The Modesto Bee reports that Peterson's lawyers allege a cadaver-sniffing dog did not pick up a scent from the fishing boat in which prosecutors says Peterson transported his wife's body before dumping it.
Defense lawyers made the claim as part of a bid to challenge evidence obtained from wiretaps on Peterson's home. They claim the prosecution failed to mention the dog story when seeking warrants for the wiretaps, when any exculpatory information must be disclosed.
Laci Peterson, disappeared from her Modesto home on Christmas Eve. She was eight months pregnant at the time. The bodies of Laci and her unborn son, Connor, washed up on the shoreline of a San Francisco Bay waterfront park in April.
Scott Peterson is charged with two capital murder counts.
According to the Bee, defense attorney Kirk McAllister wrote that the dog evidence "destroys the theory on which the prosecution has based its case."
Prosecutors would not comment.
Legal experts said that if true, the dog evidence was damaging to the prosecution case but did not destroy it.
On Friday, a preliminary hearing for Peterson was delayed from Oct. 20 to Oct. 28 because of a scheduling conflict. Prosecutors are expected to outline their case in detail at that hearing.