Scott Peterson's Ex-Mistress May Testify Monday

The former girlfriend of accused murderer Scott Peterson (search) might have to testify for his defense team on Monday, if his lawyers have their way.

In a stunning move, Peterson's defense attorneys were reportedly planning to subpoena Amber Frey (search) to testify in the preliminary hearing, Fox News learned Friday.

Frey has long been thought to be the cornerstone of the prosecution's case and damaging to the defense.

Defense attorney Mark Geragos (search) planned to serve Frey with the subpoena between 11 a.m. and noon EST, but there was no word on whether he had been able to by Friday afternoon. The subpoena states that she is scheduled to appear in court on Monday.

Legal experts believe there's only a remote chance the judge will allow the defense's subpoena to go through.

"It's unlikely that the court would permit her to testify," Frey's lawyer, Gloria Allred (search), told Fox News. "If the court requires her to testify, she'll be there. She'll be ready."

Allred said she didn't know whether her client had been subpoenaed, but speculated on what Peterson's attorneys might do.

"The defense might try to revictimize her, try to attack her, for cooperating with law enforcement," she told Fox.

The preliminary hearing, which opened Oct. 29, was expected to end Monday or Tuesday, unless Frey winds up testifying or the subpoena issue causes further delays.

Fox News legal analyst Stan Goldman said he expected the defense to appeal the subpoena matter if they aren't granted their request, which would force a continuation of the preliminary hearing.

Goldman said the chances of honoring the defense request were "not high" because California has laws protecting victims from taking the stand at preliminary hearings. He said that law might apply to Frey.

"She may not be the victim in this case, but the prosecution may be allowed to use the law" to keep her off the stand, Goldman said.

It's unclear why Peterson's lawyers want Frey, a 28-year-old massage therapist and single mother, to testify. There was much speculation that she would appear on behalf of the prosecution, but they decided not to call her, reportedly fearing that cross-examination would drag on for days.

Frey has said she became involved with Peterson without knowing he was married. She began cooperating with police shortly after she came forward with her story of the affair.

She received hundreds of calls from Peterson even after his pregnant wife, 27-year-old Laci Peterson (search), disappeared Christmas Eve. Many of them were taped via police wiretapping.

Allred said it's likely Frey will be a witness at the trial.

"I do expect she'll be testifying in the trial," she told Fox. "There's a lot of stress, a lot of tension about this case and the impact it's had on her, but she recognizes that Laci and Conner have been murdered and it's her duty to testify if she's called."

During Friday's testimony, a police detective acknowledged that he didn't follow up on a tip from a woman who claimed to have seen someone resembling Laci in a park on the day her husband says she disappeared.

Under cross-examination by Peterson's attorneys, Detective Philip Owen said he didn't pursue the tip because he didn't think it was "going in the right direction."

Peterson's attorneys have suggested during the preliminary hearing that detectives zeroed in on Laci Peterson's husband as a suspect, and ignored other leads.

Owen said he didn't feel the woman's tip was credible because it conflicted with other information detectives had received.

The woman, an employee at the Stanislaus County Hospital, told police she saw a woman who resembled Laci Peterson walking a barking golden retriever in the park near the Peterson home at around 10:45 a.m. on Dec. 24. The tipster reported that two men walking near the woman told her to shut the dog up.

On Thursday, Karen Servas, who lived near the couple, testified that she found Laci Peterson's golden retriever wandering in the street at "approximately 10:18 a.m."

Fox News on Friday learned that Geragos was considering calling another witness, a city worker who saw Peterson backing up his boat at the Berkeley Marina and laughed at him because Peterson didn't seem to know what he was doing.

The witness could help Peterson's case, since the story places him in the boat at the marina at a certain time.

Geragos was also expected to ask for a change of venue soon after the preliminary hearing is over, Fox News has learned. He thinks the trial will begin sometime between February and July, sources close to the case told Fox.

On Thursday, Detective Owen testified that Laci's remains washed ashore in San Francisco Bay in tan pants — not the black pants her husband reported she was wearing when he says he went fishing on Christmas Eve.

Owen said the pants matched a pair bought on Peterson's account at a Modesto maternity store. Her half sister, Amy Rocha, testified she was wearing tan pants on Dec. 23 — the last time anyone other than her husband has reported seeing her alive.

Prosecutors contend that Scott Peterson, a 31-year-old former fertilizer salesman, killed his pregnant wife later the night of Dec. 23 or early the next morning and then used a fishing boat to dump her body in San Francisco Bay.

Fox News' Rita Cosby, Stan Goldman, Catherine Donaldson-Evans, Shepard Smith and The Associated Press contributed to this report.