Where is Kristin Smart? Search warrant served at killer's mother's property after remains detected

LOS ANGELES - Nearly three decades after Kristin Smart disappeared, San Luis Obispo County Sheriff's investigators on Wednesday served a search warrant at the home of her killer's mother and prepared to scan and sample the grounds for her remains.

The Arroyo Grande home belongs to Susan Flores. Her son, Paul Flores, was the last person seen with Smart as the two walked toward her dormitory at Cal State San Luis Obispo after a 1996 Memorial Day weekend party. He was sentenced to 25 years to life in prison three years ago for Smart's murder. But her body has never been found.

Three years ago, a group of scientists working from Susan Flores' neighbors' backyard using soil vapor sampling detected the presence of volatile organic compounds that they say may be associated with decomposing human remains.

A sheriff's detective served Susan Flores with the search warrant shortly after 7 a.m., and also have access to a neighboring home where the scientists in 2023 detected the volatile organic compounds. The grounds have been searched before. Sources familiar with the investigation said the search is expected to last two days.

"The San Luis Obispo County Sheriff's Office is conducting an additional investigation into the property in the 500 block of East Branch Street in Arroyo Grande. This investigation is related to the Kristin Smart disappearance," the Sheriff's Department said in a statement. "This activity is the result of a search warrant signed by a Superior Court judge. The Sheriff's Office remains committed to bringing Kristin home to her family."

San Luis Obispo County Sheriff Ian Parkinson, along with investigators and experts in ground-penetrating radar and soil science, appeared at the home Wednesday morning. Sheriff's officials confirmed a search warrant is being served. The department said it won't be commenting beyond the statement.

Among those at the scene was Tim Nelligan, a soil engineer who, along with another scientist and an FBI research chemist turned professor, found signs suggesting human remains from the data they gathered in the area. Subsequently, the Sheriff's Department asked for additional data and academy research to support their new method for detecting remains using soil vapor.

The group used a technology known as soil vapor sampling, which they say could detect volatile organic compounds associated with decomposing human remains. Although the practice is still in the theoretical research stage, scientists have spent two decades studying the chemical compounds associated with the breakdown of the human body.

The Sheriff's Department has previously said officials have also been in touch with the FBI about the research. The science at that time was unproven and has never been used in any criminal proceedings, but the group told The Times they are confident in their findings.

Soil vapor sampling

Nelligan, an environmental engineer from San Clemente, met Smart in college. He recalled her knocking on his door and asking to use his landline phone.

"It was this 6-foot-tall, attractive girl by herself, who introduced herself as Roxy," said Nelligan, referring to a nickname Smart used from a clothing brand she favored.

A week and a half later, he said, her disappearance was all over the local TV stations.

Nelligan said he didn't know Smart's family, but he'd always wished he could help.

The public's on-again, off-again interest kept Smart's disappearance in the news sporadically, but a podcast called "Your Own Backyard," begun in 2019 by Chris Lambert, shined a new spotlight on the cold case.

In November 2019, he began researching how bodies decompose in soil. Two months later, he recruited Steve Hoyt, another Cal Poly grad with a doctorate in environmental science who has built a business on the Central Coast testing soil samples. Brian Eckenrode, a retired FBI forensic scientist and expert in human decomposition, joined them in 2021.

Authorities had repeatedly searched the backyards of homes owned individually by the parents of Paul Flores. Sheriff's deputies even used ground-penetrating radar and cadaver dogs to search Ruben Flores' Arroyo Grande property in 2021. No remains were uncovered, but a month later, both Flores men were arrested and charged in connection with Smart's murder.

In 2023, trio keyed in on the Arroyo Grande home of Susan Flores, a short distance from Ruben Flores' house. The property had been the subject of search warrants in the past - including one that stemmed from civil litigation with the Smart family.

Nelligan contacted neighboring homeowner Marcia Papich, whose fence abuts Susan Flores' backyard. After digging holes in the dirt near the property line, Nelligan pushed a small tool known as a soil vapor probe, with a long, straw-like attachment, about three to five into the earth. Any gases the probe encountered were then vacuum-withdrawn and collected, then sealed in a canister. The extracted volatile organic compounds were then sent for analysis at a San Luis Obispo laboratory operated by Hoyt.

What showed up when those compounds were represented with colors on a plume map and compared with dozens of control-point samples of nearby soil indicated the presence of a decaying body, according to Eckenrode.

Susan Flores has never been charged in connection with her son's crimes. During the search three years ago, she maintained that he didn't kill Smart and that her family doesn't know the missing student's whereabouts.

Attorney Harold Mesick, who secured a not guilty verdict in Ruben Flores' accessory charges, told The Times in 2023 the idea that a body could be in Susan Flores' yard is "ludicrous."

He suggested that if authorities were looking for Smart's remains, they should expand their investigation into who truly took her, maintaining that the Flores family had nothing to do with her disappearance. Mesick reiterated that nothing had ever been found in multiple searches of both Susan and Ruben Flores' yards, and said that authorities caused $30,000 in damage to Ruben Flores' property by digging below his deck - a search that yielded nothing.

Of course, the researchers cannot say whose remains might be in Flores' yard or when they may have been buried. But the trio was confident in 2023 they'd detected a body in the ground.

Now the search is back.

The Branch Street house had first come under scrutiny a few months after Smart went missing. Mary Lassiter was renting the pale-blue two-story home. She found an earring in the driveway and turned it in to authorities.

But before the earring could be examined, it was misplaced, officials said. When interviewed for the podcast "Your Own Backyard," Lassiter said the earring matched the necklace Smart is wearing in photos that went up after her disappearance.

Even stranger was the beeping that awakened Lassiter one morning.

"It sounded like a digital watch alarm," she said of the noise coming from the backyard. Months later, the sound stopped.

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This story was originally published May 6, 2026 at 3:52 PM.