Amber Frey (search) on Tuesday revealed to a jury intimate details of her affair with Scott Peterson (search), who is on trial for the murder of his pregnant wife.

Their first night together, a blind date, included slow-dancing in a karaoke bar before going to a nearby hotel, testified Frey, who wore a black suit and diamond cross necklace. She said Scott went to some lengths to romance her, pouring champagne and putting a strawberry in her glass.

They had sex later that night, she said. The next morning, he left her with his cell number, not his home number.

Frey, the government's star witness, revealed the first details of the affair the prosecution says led Peterson to murder his pregnant wife Laci.

She held a black bag in front of her face to block the cameras as she was driven to the courthouse, and then spoke so softly on the witness stand that the judge had to ask her to get closer to the microphone.

With short, clipped answers to questions from prosecutor Dave Harris, Frey said Peterson wasn't wearing a wedding ring that night, Nov. 20, 2002, a little more than a month before Laci Peterson (search) vanished.

Frey said on their second date, Scott Peterson carried her 22-month-old daughter as they went hiking. Later that day, he gave the little girl a children's book. Then, he cooked seafood lasagna with wine before they had sex again.

"He made the comment that there would be many more corks ... many more bottles to share," testified Frey.

The next day, Dec. 3 — she gave Peterson a car seat and the key to her house, and asked him to pick up her daughter at day care.

"He said he would be honored," recalled Frey, who returned home to find him warming up the previous night's dinner. Then all three went out to buy a Christmas tree, and after decorating it, Frey and Peterson had sex for a third time.

The testimony about the intensity of their early relationship appeared to counter one aspect of Peterson's defense — his lawyers have scoffed at the idea that a man would murder his pregnant wife to be with a single mother he had just met.

But Frey said that from the beginning, Peterson seemed to want a future with her. The next time they saw each other was Dec. 9, Frey testified, when he told her he had lied about never being married.

Then, she said, he began to cry and told her "he had lost his wife."

"He said this would be the first holidays he would be spending without her," she said.

At the time, Frey said she understood Peterson to mean that his wife was dead. "I thanked him for sharing that with me," she said, adding that she asked him if he still wanted to have a serious relationship with her. "He said absolutely," she said.

About two weeks before Laci disappeared, Frey testified that she and Peterson were together once more. They discussed their future together, she said, and Peterson promised to care for her daughter. "He would consider her his own," she recalled him saying.

Prosecutors also showed jurors a series of holiday pictures showing Frey and Peterson embracing and smiling. One showed Peterson grinning in a Santa Claus hat.

Frey has not been cross-examined -- an opportunity the defense likely won't get for at least another day.

Shawn Sibley (search), the woman who fixed Peterson up with Frey, testified earlier that she had confronted Peterson on Dec. 6 after learning he was married. He had also told her he "lost" his wife, she said. Sibley said Peterson begged her to let him break the news to Frey.

Prosecutors appear to be trying to show that Peterson began hatching the murder plot a day later. Evidence shows he searched for used boats on Dec. 7-8, as well as numerous Web sites for fishing information, currents in San Francisco Bay and details on boat ramps in the area.

Prosecutors allege Peterson killed his wife in their Modesto home on or around Dec. 24, 2002, then drove to the bay and dumped her weighted body from a small boat he had purchased just weeks earlier. The badly decomposed remains of Laci Peterson and the couple's fetus washed ashore in April 2003, not far from where Peterson said he launched a solo fishing trip the day she vanished.

Before Frey began her testimony, Judge Alfred A. Delucchi met privately with lawyers, but no details were released about the session. Last week, the judge delayed the trial so that both sides could investigate recently discovered evidence.

Defense attorney Mark Geragos (search) called that evidence "potentially exculpatory." Prosecutors have not commented on the evidence questions, citing the judge's gag order.

Gloria Allred (search), Frey's lawyer, said outside court that once Frey learned that Laci was missing, she immediately informed law enforcement.

The subsequent conversations between Frey and Peterson that were taped as part of the murder investigation make for "compelling and riveting" evidence, said Allred, who predicted that Frey would be on the stand for "a considerable amount of time."

"We are going to hear about the quality and the depth of that relationship [between Peterson and Frey] and how that relationship developed and evolved over time. We are going to hear about how Scott Peterson wormed himself into Ms. Frey's life and into her heart," Allred said.

Prosecutors played some of the phone conversations, beginning Dec. 30, 2002, in which Peterson tells Frey he is in New York and later in Paris. Prosecutors believe Peterson actually was in California.

"I'm on the uh ... near the Eiffel Tower and the New Year's celebration is unreal," he said on one call.

The Associated Press contributed to this report.