"We haven't been able to eliminate him for a long while," Modesto Police Chief Roy Wasden said. "You look to eliminate possibilities and that's what we kept doing and Scott could just never be eliminated."
Scott Peterson (news - web sites), 30, is now in custody, likely facing double murder charges, after DNA tests identified bodies found about three miles from the marina as 27-year-old Laci Peterson and her infant son, his umbilical cord still attached.
Police had pursued nearly 10,000 tips, and looked at parolees and convicted sex offenders as possible suspects, but they kept returning to one person: Scott Peterson.
The fact that no credible information was ever received on tip lines even when the award was boosted to $500,000 also kept investigators focused on Scott.
"Had anyone known about where Laci was, had any information about where she was and if she was alive, we would have heard about it," Wasden said.
On Friday, hours before the DNA test results were announced, plainclothes agents who had been tracking Scott Peterson with phone taps and vehicle sensors pulled him over in the San Diego area and arrested him.
Attorney General Bill Lockyer said they feared Scott Peterson might try to flee. His dark hair had been bleached blond and he had a beard.
He was booked into the Stanislaus County jail late Friday and is expected to be arraigned Monday or Tuesday on two counts of capital murder. District Attorney Jim Brazelton didn't say if he would seek the death penalty.
Peterson's attorney, Kirk McAllister, did not return telephone calls seeking comment Saturday.
Police have refused to describe the evidence they have against Peterson or say how Laci died. Modesto Police Chief Roy Wasden said it appeared she was killed the day before Christmas because no "credible witness" saw or heard from her after that.
On Saturday morning, Modesto residents showed up with flowers, candles and Easter bunnies in front of Scott and Laci Peterson's home. Some children brought their toys for Laci's child, whom she had named Connor. Others stood with their families and prayed.
As Michelle McKinney watched her 12-year-old son place a blue and gold teddy bear in front of the house, she wiped away tears.
"The baby didn't get a chance to live his life and grow up," said McKinney, 33, clutching her 10-year-old daughter. "She didn't get a chance to enjoy her baby. My children are my whole life."
Many in this central California city of 200,000 never met the 27-year-old woman with the big smile and dimples, but many felt they knew her.
A makeshift wooden cross covered with aluminum foil on the Peterson lawn reads: "We prayed everyday that Laci and Baby Connor would come home. Now, Laci and Baby Connor are home with the Lord."
Authorities have refused to speculate about a motive in the deaths.
Scott and Laci seemed like a picture-perfect couple: Family photos show them leaning in close and smiling. Friends say they never argued.
Scott and Laci met in San Luis Obispo, where he worked three jobs to put himself through college.
"The moment he was with Laci, they just beamed at each other," his mother, Jackie Peterson, told the Modesto Bee. "No one else ever made my son smile like that. They did everything right."
She refused to comment on her son's arrest. "I'm not talking until they resolve this whole thing," she told the Contra Costa Times.
The couple married in 1997 and ran a cafe in San Luis Obispo. They sold the place two years ago and moved to Modesto to be closer to her family.
After Laci became pregnant, Scott "put a lot of hours into making that baby room just right," family friend Guy Miligi told the Modesto Bee. "He was real excited about having his first child. He talked about that all the time."
For weeks, the couple's family and friends staunchly stood behind Scott Peterson.
Laci's brother, Brent Rocha, said in January that Scott loved his wife too much to ever harm her. Her friends said he was a devoted husband.
"Scott is devastated," Laci's stepfather, Ron Grantski, said in January. "I know what we're going through, but he's got double. The press is questioning him, but all he wants to do is find his wife."
Days later, Laci Peterson's family severed ties with him after learning he had an affair with another woman. They publicly called on him to help police, who labeled him "uncooperative."
After the rift with his in-laws, Scott Peterson launched his own search effort, distributing fliers in Los Angeles while searchers looked in San Francisco Bay and near Modesto.
Many of his Modesto friends began to shun him. His fellow golfers at the Del Rio Country Club quietly bought out his membership for an estimated $25,000 in cash.
He eventually moved to San Diego, his hometown.
There, he was aware of the surveillance, waved at detectives and was "being kind of a smart aleck" before Friday, said California Attorney General Bill Lockyer.
Wasden sought an arrest warrant Thursday, a day before the confirmation of the identities of the bodies, in part because he feared Peterson might flee to Mexico, which forbids the extradition of anyone who faces the death penalty.
"That was a concern," Lockyer spokesman Nathan Barankin said Saturday. "While we've improved our relationship with Mexico, extraditions, death penalty or not, can be very troublesome, expensive and tiresome."