The attorney for the inmate who claimed double murder suspect Scott Peterson (search) plotted the kidnapping of his pregnant wife may have "corroborating evidence" as early as Monday, Fox News has learned.

Frank Muna, the attorney representing Cory Lee Carroll (search), told Fox News he hopes to soon produce documentation, and possibly a witness, placing Peterson at locations in Fresno where he allegedly met with two members of a neo-Nazi prison gang.

Carroll, a parolee jailed since August after missing a court date, told investigators that he introduced Peterson to the two Nazi Low Riders (search) members on Nov. 29, shortly after meeting him in a Fresno strip club.

According to Carroll's account, Peterson initially said he wanted to find someone who would steal his wife's car as part of an insurance scam, but that talk in the meeting turned to kidnapping, at which point he left the Fresno motel room because he did not want to be involved.

Laci Peterson (search) went missing from her Modesto home on Christmas Eve, and her body, along with that of her unborn son, Conner, washed ashore on the San Francisco Bay in April. Scott Peterson was arrested for their murders shortly thereafter.

Carroll disclosed the story in June only after recognizing Scott Peterson on television, Muna said. Muna notified law enforcement after his client passed a polygraph test administered by a former Fresno police lieutenant.

The former officer, Lt. Melvin King, told Fox News, "Mr. Carroll was able to convince me that he truly believes what he's saying has some validity to it."

But the self-described petty property criminal's credibility has recently come under question.

A spokesman for the California Department of Corrections disputed Carroll's claims that he had not stepped forward earlier because he was in prison lockdown and had no access to media reports for months.

The spokesman told Fox News on Saturday Carroll's story was "simply not true."

In addition, Janey Peterson, Scott Peterson's sister-in-law, told Fox News she, her husband, and Scott and Laci Peterson were together in San Diego on Nov. 29 and that it would have been impossible for Scott Peterson to have made the alleged trip to Fresno.

In other developments, Fox News has learned that Peterson and his mistress, Amber Frey (search), were in frequent contact around the time of his wife's disappearance.

According to phone records, Peterson and Frey spoke at least twice on Christmas Eve, the day Laci Peterson went missing.

The following day, they spoke again at 8:23 in the morning, and at least three more times afterward.

Frey called Peterson 13 times on Dec. 26. The 28-year-old single mother and massage therapist has said that she did not know that Peterson was married and that his wife was missing until Dec. 29. At 1:43 a.m. the following day she called Modesto police and informed them of her relationship with Peterson.

Those familiar with the prosecution's case have told Fox News that it will hinge on Peterson's love for Frey as the motive in the double murders. Frey will play a lead role and lawyers are currently preparing her to take the stand at the Oct. 20 preliminary hearing, the sources said.

On Valentine's Day, Peterson phoned Frey seven times to say he was in love with her and wanted to see her, sources in the investigation told Fox News.

Fox News' Rita Cosby contributed to this report.