The jury's ears have been on Frey for five days in a row - listening to the tapes she made of phone conversations with Peterson - wiretapping she agreed to after going to police, a decision she said was made when she found out he was married and a suspect in what turned out to be his wife's murder.
All of the calls were made during the period in which police and volunteers were searching for Laci Peterson, who Scott reported missing in December 2002 and whose body was not found until several months later.
While Peterson seemed to speak freely - serving up numerous obvious lies - in the first batch of taped conversations, a later tape - played in court Tuesday - hints that he did realize cops might be listening in to his remarks.
In the recordings, Peterson often sounded apologetic for lying to Frey about being married, but he also was evasive.
In a call Feb. 7, 2003, Peterson tells Frey he will be spending the night in Sacramento and says he will call her the next day from a pay phone. Frey then asks Peterson why he is going to Sacramento.
"I can tell you, but not on these phones," he says, in an apparent reference to his calls being monitored. It was unclear whether Peterson knew Frey was taping him.
Authorities hope to show jurors Peterson's affair with Frey was his motive for killing his wife and their unborn child.
Prosecutors allege Peterson killed his wife in their Modesto home on or around Dec. 24, 2002, then drove to San Francisco Bay and dumped her weighted body from a small boat he had purchased weeks earlier. The 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.
His attorneys claim he was framed after the real killer learned of his widely publicized alibi. They acknowledge his affair with Frey but said that being a "cad" doesn't make him a killer.
Frey has testified that she called police after discovering her lover was married and a suspect in the disappearance of his pregnant wife.
Frey took the witness stand briefly Tuesday, telling jurors about her first public statement on the case given to the media on Jan. 24.
"I spoke of the relation with Scott and... and I spoke of my hopes for Laci's safe return, as well," Frey said.
Jurors then heard a taped call from Jan. 25, during which Peterson continues to romance Frey.
"It's incredibly brave. It just shows what amazing character you have," Peterson says to Frey about her media appearance, constantly referring to her as "sweetie."
On another call, Peterson expresses frustration that Laci's family "is accusing me of having something to do with it now."
Amber replies angrily that she even was questioned by a detective about her whereabouts the day Laci vanished.
"How could I not possibly think you have something to do with this, Scott?" Amber asks.
"The only way is that you know me well enough to know I could never do anything like this," Peterson replies. "Amber, it just hurts so bad for you to think I could have something to do with this."
During a Feb. 7 call, Peterson is heard sobbing throughout the conversation, saying "You know I'm not a monster, Amber."