The woman who introduced Scott Peterson (search) to his mistress testified Wednesday that when she first met him, Peterson never mentioned he was married and he told her he had "lost" his first love.

Peterson then turned the conversation to sex, Shawn Sibley (search) testified.

"We'd be talking about something else and he'd bring up sex," she said. "He did ask me my sexual preferences ... sexual positions ... but he was kind of joking."

She later introduced Peterson to his future girlfriend, massage therapist Amber Frey (search).

Prosecutors claim it was that affair that drove him to murder his pregnant wife, Laci.

Sibley said she met Peterson at an agriculture conference in October, 2002 and he told her he hadn't "been successful in finding anyone for himself," and that he was looking for a "long-term relationship with someone."

Sibley said she "freaked" when she learned through an acquaintance that Peterson was married.

She called him and confronted him.

"He kept denying it," Sibley said.

He later called her and left a message on her cell phone.

"Scott's just sobbing hysterically ... He says, 'I'm so sorry I lied to you earlier. I had been married. I lost my wife,"' Sibley recalled of the message.

Peterson persuaded Sibley to let him tell Frey the "truth," that he had been married, but his wife died.

Sibley later became so suspicious, she testified, that she used the Internet to find out whether Peterson was married, though she didn't find any information.

"Once we found out that Scott was connected to the missing Modesto woman, Amber immediately called the police," Sibley said.

On cross-examination, defense lawyer Mark Geragos (search) prodded her about the sex talk with Peterson.

"It was a two-sided discussion?" Geragos asked.

"Yes," Sibley replied.

He pushed even further.

"Is it unusual at conferences for people to drink and say stupid things," Geragos asked.

"No," Sibley said.

"You ever know married men to act idiotic," he pressed.

"Yes, but I've never known a married man to lie to me about being married," Sibley said.

Shocked, Geragos replied, "Really?"

Prosecutors allege Peterson, 31, murdered his pregnant wife on or around Dec. 24, 2002, at least in part because of the affair. They say he then dumped her body in San Francisco Bay.

Defense lawyers say someone else abducted her near their Modesto home as she walked the dog, and held her captive before killing her and dumping her body to frame Peterson.

The trial ended shortly before lunch Wednesday and won't resume until Tuesday. Judge Alfred A. Delucchi gave jurors an extended break for the holiday weekend.

Before leaving the courtroom, Delucchi admonished the jury: "Don't be looking at anything about this trial," adding he knew it would be "tempting" for them to read media accounts of the case.