"I've never done this before," she sobbed, "but I'm very compelled now."
Shelton is convinced the bodies are the remains of Laci Peterson and the baby she was carrying when she vanished on Christmas Eve.
"I know it's her," she told CBS News Correspondent John Blackstone, "and I'm just glad she's come back to us, to help us find what's happened to her. She's the only one who knows."
State crime lab technicians are analyzing DNA swabbed from the mouths of Sharon and Dennis Rocha — Laci's parents — to compare samples from the severely decomposed corpses found a mile apart this week on the rocky shoreline of this city east of San Francisco.
At this point, the scope of their identification work is limited to determining if the months-long search for Laci Peterson and the baby boy she was due to deliver in February is over, authorities said Wednesday.
"We don't have another person in mind," said John Tonkyn, a missing persons supervisor at the Attorney General's Richmond DNA Laboratory.
It could be days more before a determination is made.
"A rush case would typically take about a week," he said. "It doesn't happen in an hour."
Peterson, 27, was eight months pregnant when she vanished from her Modesto home on Christmas. Her husband, Scott Peterson, said he last saw her that morning as he left to go fishing in Berkeley, 90 miles northeast of Modesto and three miles south of where the bodies surfaced.
In addition to testing specimens from Peterson's mother and father, the lab in Richmond will also compare tissue and bone from the two unidentified corpses with DNA extracted from strands of hair taken from Laci Peterson's brush.
When asked why dental records weren't being used, Tonkyn said the lab wasn't provided with teeth.
"Sometimes not a full skeleton has been found," Tonkyn said.
Published reports have said the woman's body was headless. The full-term baby still had an umbilical cord attached.
If the woman's body is not identified as Peterson, the lab will begin comparing the samples with likely matches in a database of 100 DNA samples of other missing people or their relatives. The state has more than 25,000 active missing person cases.
"I'm hoping that what they found is her so that way the family has closure and we all have closure," said a Modesto resident.
Scott Peterson, Laci's husband, hasn't been seen in Modesto in weeks. His attorney refuses to say where he is. Investigators have never named Peterson as a suspect but when he admitted having an affair, many in Modesto made their own decision.
"If he comes out innocent, I think we'll all feel badly and go out and apologize to him, but right now he makes people nervous," said Modesto resident Kim Grise.
While his in-laws stood by him early in the investigation, a rift developed after Peterson acknowledged having an affair with a Fresno woman and traded in his wife's Land Rover for a new pickup truck.
Laci Peterson's father, Dennis Rocha, told CBS station WBZ-TV in Boston Wednesday that he thinks it's only a matter of time before his son-in-law is charged in the case.
"I just can't see Scott being out there free," Rocha told the television station. "That would just eat me up." He predicted that an arrest "will happen very soon."