MODESTO, Calif. -- In a tear-stained press conference Friday, the family of Laci Peterson publicly pleaded for her safe return and begged her husband, Scott, to cooperate fully with Modesto Police.

Stunning Developments Of Jan. 24 Amber Frey Comes Forward Rocha Family Press Conference

Appearing before the national media for the first time in more than a week, Laci's brother -- Brett Rocha -- said that Scott had admitted to him he was having an affair.

"On Jan. 16, 2003, by telephone Scott Peterson admitted to me he was having an affair with a Fresno woman," Rocha said. "I confronted him after viewing pictures of him with this woman."

The family was shown four photos of Scott and the woman by Modesto police a little over a week ago. They were also told Scott had taken out a $250,000 insurance policy out on Laci Peterson's life.

Since that meeting, the family has distanced itself from Scott.

"I would like Scott to know I trusted him and stood by him in the intial phases of my sister's disappearance," Rocha said. "However, Scott has not been forthcoming with information regarding my sister's disappearance and I'm only left to question what he might be hiding."

He added, "because we have so many questions, I can no longer support him."

Laci's mother -- Sharon Rocha -- made an impassioned plea for her daughter's return.

"Since Christmas Eve, our one and only focus has been to find Laci and bring her home to us," she said choking back tears. "I love my daughter and miss her every minute of every day. I miss seeing her. I miss our talks together. I miss the excitement in her voice when she talks about her baby...Someone has taken all this away from me."

Hours before the Rocha family press conference, another one-time supporter of Scott Peterson said he too now questioned the Modesto man's motives.

Brad Saltzman, who manages the Red Lion Inn in Modesto, the site of the now closed Laci Peterson search center, said Thursday night his support for Scott has waned since last weekend's efforts in Westwood.

The hotel used as the headquarters for that search is run by the same ownership group as the Modesto Red Lion and Saltzman was a key figure in setting it up.

Video

Ted Rowlands: Friday Report

"It's funny because last week a correspondent asked me if I had ever seen Scott cry," he said. "I thought about it, and I've seen other family members cry but I had never seen Scott cry. His demeanor was like it was empty, and he liked the attention from the media."

"I was able to take him the back way (in the hotel). I was able to take him up the service elevator, but he chose to go in front of the media and it was a media circus out there. That's why I think he intentions weren't to find Laci."

Saltzman said he also felt he and other volunteers had been used by Peterson.

"I put in endless hours as a volunteer to help him, and when he was done with the volunteer efforts he packed his car and left," he said. "There was a thank you and goodbye, (but) it made me wonder what his real motives were."

"Unfortunately I don't think it was to find Laci. I think it was to look good in front of the media, and to show him shaking hands with volunteers, and that's not right because of all these people who have put in countless hours to help find Laci. It's not right."

Peterson had not responded to Saltzman's comments on Friday. But there were other developments in the case of the missing mother-to-be who vanished from her home on Christmas Eve day.

A search scheduled for San Diego this weekend had been delayed by a week. There was no explanation for the delay from Scott or his family.

Video

MSNBC's Dan Abrams Talks About The Case

Among the national media gathered in Modesto for the Rocha family news conference was Dan Abrams, the legal correspondent for MSNBC.

"It's impossible to know what evidence they have," Abrams said of the case. "I don't think the body, if she is dead, will be the key to the case. I think it will be the physical evidence."

Scott Peterson has repeatedly said he had nothing to do with his wife's disappearance and was cooperating with police.

It's been a month since Laci disappeared. At the time, Scott Peterson has told authorities he was on a day fishing trip to the Berkeley Marina in the Bay Area.

When he arrived home, his wife -- who was more than eight months pregnant -- had vanished.

At the state crime lab in Ripon, about eight miles from Modesto, investigators continued Friday to pour over the evidence sent to them by Modesto police.

John Yoshida, a member of the crime lab staff, told KTVU Wednesday that "a lot of evidence" had already been processed in the case and returned to the investigators.

"We have processed a lot of things," he said. "And as the case changes, we change our priorities. We continue to get evidence in all the time."

Yoshida said the latest advances in forensic medicine have changed the way cases like Laci Peterson's are handled by police.

"We've done several cases (that have) been bodyless," he said. "In other words, no body has ever been found. Certainly as good as the science now is, it's easier to get a conviction. A lot of times, what we see is because the science is so good, it never sees the light of day."

"What we get is a lot of pleas because they (the legal system) trust the science much more now."

While work at the lab goes on, Modesto Police say they continue to track down leads in the case. However, they have not revealed where, or if, any new searches were currently underway..