The same day he bought a fishing boat that would provide his alibi when his pregnant wife vanished two weeks later, Scott Peterson (search) told his mistress he was a widower planning his first Christmas alone, a police officer testified.

Detective Allen Brocchini, who launched the Christmas Eve investigation into Laci Peterson (search)'s disappearance, said Scott Peterson bought the boat Dec. 9 — the same day Fresno massage therapist Amber Frey (search) later told the officer that she confronted Peterson about being married.

While Brocchini did not link the two events that happened that day, he provided the pieces of the puzzle prosecutors are assembling to show Peterson was plotting the demise of his wife weeks before he returned from his Dec. 24 fishing excursion and reported her gone.

Brocchini's testimony Thursday in the preliminary hearing revealed the details he gathered from the day Peterson claimed he was motoring his 14-foot skiff on San Francisco Bay to his arrest nearly four months later in San Diego.

Peterson was arrested driving a Mercedes convertible be bought for $3,600 cash, using his mother's name, "Jacqueline Peterson."

When asked about the peculiar name, he told the seller it was the name his parents gave him, Brocchini said.

In the first hours of the investigation, Peterson denied he was having an affair, Brocchini said. Peterson never told him about Frey.

On Dec. 30, Frey placed one of the hundreds of calls Modesto police received each day. Brocchini was watching a clerk type notes from the caller and decided to pick up the phone and handle the call himself.

The detective then drove 90 miles to Fresno to interview Frey, a single mother.

Frey said she met Peterson on Nov. 20 and he said he was single. But she later became suspicious and confronted him about three weeks later because she thought he was married.

"He said he lost his wife, this would be the first holiday he was without his wife," Frey told Brocchini.

Peterson called Frey on Christmas and the following three days, Brocchini said. At some point, he told her he was out of the country and would be able to spend more time with her after Jan. 25.

Frey began taping their phone conversations for police, and investigators tapped Peterson's phones for evidence.

Frey may testify later in the hearing that will determine whether the 31-year-old former fertilizer salesman is tried on charges of murdering his 27-year-old wife and unborn son. Prosecutors are seeking the death penalty.

The hearing will resume Wednesday.