LOS ANGELES — Scores of sheriff’s deputies and federal agents dug up dirt at three sites at Cal Poly San Luis Obispo University last week, looking for the body of Kristin Smart.

The freshman, nicknamed Roxie, vanished 20 years ago after going to a fraternity party during Memorial Day weekend 1996. Lawmen were led here by a trio of the FBI’s own Quantico-based Springer spaniels and German shepherds who hoped they got a human cadaver hit at three spots along the hill in January.

Her anguished parents Stan and Denise said in a recent statement their hopes are “tempered” but endorse the dedicated effort to track down their missing daughter and wish “the ‘person of interest’ will soon be held accountable for taking her life and harboring her remains for over 20 years.”

Experts and neighbors tell The Daily Beast they might be digging in the wrong spot, and that they have reason to believe Smart may be buried in the backyard that once belonged to the last man seen with her.

In 2000, FBI Special Agent Jack Schafer did his own private investigation into Smart’s disappearance, reviewing sheriff’s reports, witness statements, a civil lawsuit, and interviews conducted by law enforcement with the prime suspect: Paul Flores.

“I believe Kristin Smart is deceased and that her death and/or disposal of her remains are a result of a criminal act,” Schafer concluded.

On her last night alive, according to Schafer’s report citing official investigative documents, Smart, a 19-year-old, blond, 6-foot-1 swimmer was passed out drunk on a lawn around 2:30 a.m. after partying at an off-campus home on Crandall Way hosted by Kappa Chi fraternity.

A group of students rousted her awake. Once she was up, Smart involuntarily clung onto a troubled Cal Poly interloper named Paul Flores who joined the handful of students retreating for the night to the dorms.

Flores, also 19, who barely knew Smart before that night, told investigators she was “walking real slow” and put his hands on the drunken teen’s waist allegedly to keep her warm from the early-morning chill of May 25, 1996.

“… a couple times like on the way, maybe probably twice you know, I went like that just gave her kind of a hug ’cause she was freezin’,” he told Cal Poly’s campus cops, according to Schafer’s report. Flores said he left Smart at her room at Muir Hall before crashing at his room in nearby Santa Lucia Hall.

“OK um, she walked that way, I walked that way,” Flores told campus cops. “That’s the last time I saw her.”

A missing person’s report was produced on May 28, 1996, and in it Smart’s roommate noticed that none of her belongings—ID, toiletries, or clothing—had been missing from her dorm.

On June 29, 1996—more than a month without a sign of Smart—authorities were led by cadaver dogs roaming the campus to room No. 128 in Santa Lucia Hall.

Flores lived there with his roommate, Derrick Tse.

More cadaver dogs were brought in and “each dog alerted on a corner of a bed mattress located on the left side of the room.” It was Flores’s bed, Tse told cops, according to a police report Schafer cited.

That portion of mattress was confiscated as evidence, and the dogs returned and again “alerted on Room No. 128” and even without the mattress “alerted on the left side of the room.” It “indicated a strong possibility that a deceased body had been in that room.”

Tse quoted Flores to police as saying, “Yes, I killed her and brought her to my mom’s and she is still there.”

On May 31, 1996, investigators from the San Luis Obispo District Attorney’s Office asked Flores about cuts on his knees and a bruise under his right eye.

He claimed the black eye was caused by taking an elbow during a game of pickup basketball with his college buddy Jeremy Moon at Harlow School in Arroyo Grande four days earlier, according to Shafer’s report quoting investigators.

But prosecutors reported they reached Moon and the story didn’t square. Flores already had the black eye “when he saw him on Sunday, May 26, 1996,” a day after Smart was reported missing, and “could not have sustained the injury playing basketball,” investigators wrote.

When Moon asked about the shiner, Flores said he “didn’t know how he got the black eye.”

The following month prosecutors interviewed Flores again.

The teen admitted he’d lied about the black eye because the warrant states he claims to have struck his face on a steering wheel “while working on his truck on May 27, 1996.”

Why lie?

Flores said “it would ‘sound stupid’ saying he bumped his eye on the steering wheel of his truck,” the report states.

Time slogged on and Flores was never charged.

The Smart family took their fight to civil court by filing a wrongful death lawsuit against Flores.

The complaint, obtained by The Daily Beast, was filed on Nov. 28, 1996, in San Luis Obispo County Superior Court. It blasts Flores for having “preyed upon the victim, Kristin Smart” who was in an “intoxicated state” and ultimately “murdered Kristin Smart on the premises of California Polytechnic State University in San Luis Obispo, California.”

It also blames the freshman for “intentionally inflicted emotional distress upon the parents of Kristin Smart by taking the body of [sic] Kristin Smart and secreting and/or destroying the body… in a hidden place in the County of San Luis Obispo.”

When Flores appeared on Nov. 14, 1997, with his attorney to be deposed, he only confirmed his name and birthdate. He was repeatedly (almost 30 times) pointed by his attorney to read from a typed sheet to invoke his Fifth Amendment privilege against self-incrimination in response to innocuous yes/no questions and mundane ones like the names of relatives or his age.

The family accused Cal Poly’s campus police of being “grossly negligent in the performance of their duties” because “critical evidence pertaining to the investigation to the murder of Kristin Smart was irretrievably lost and valuable evidence was destroyed.”

A university spokesman refused “to discuss any further details related to the Smart case while the San Luis Obispo County Sheriff’s Office excavation/investigation is ongoing.”

Before Flores was suspected in Smart’s disappearance, he was accused of stalking another female on campus. According to a March 27, 1996, San Luis Obispo police report a drunken Flores was accused “around Christmas” of attempting to break into a Cal Poly coed’s apartment. Flores allegedly “climbed up her balcony and she suspected he attempted to break into her apartment.”

The student refused to press charges, but Flores didn’t stop. The report states that he is the one who was believed to have made countless anonymous phone calls for “the last six weeks.”

Then at a party in March, according to the police report, “Flores tried to talk to her and she told him off in very strong words.”

Today Flores lives in San Pedro, California. He stepped out of his home looking to each side as if his head was on a swivel when The Daily Beast approached him on Saturday. With the coast seemingly clear he opened the door to his white 1960 Chevrolet Impala parked on the crammed street where he’s resided for almost two years.

He started the engine and began pulling off from the curb, then braked just as a Daily Beast reporter approached him.

When asked if he was Paul Flores, the last person to see Kristin Smart alive, he played dumb, at first only confirming Flores was someone who lived at the address.

“Oh, he does.”

When pressed that he was Flores the man replied, “Oh. Yeah.”

Flores rolled up the car window and reversed. He parked the car again and exited.

When asked if he remembered Smart he said, “Right. Yeah.”

Flores refused to weigh in on the feds’ search for Smart’s remains.

“I’m fine. I’m good. Have a good day,” he said.

Probed about him having a hand in Smart’s demise, Flores replied:

“No-no-no. I’m good,” he said. A 57-year-old neighbor across the street who gave only his first name, Gary, said Flores was a “nice guy” who “has never bothered me.”

He remembered that when Flores moved in somebody had come and plastered the street with posters revealing Flores’s past as a prime suspect.

“All these printouts were put up saying ‘Don’t trust him,’” Gary said. “I felt bad for him.”

In July 1996 sheriff’s deputies made the first of multiple searches of the Flores residences. They started with the home of Paul’s father, Ruben Flores.

A year later Susan Flores’s Arroyo Grande property was visited by sheriffs and this time they utilized ground-penetrating radar technology to look underground. The results after the search were inconclusive.

They may have been following up a tip made by a 21-year-old food prep cook. He lived directly across the street and saw something that haunts him “like it was yesterday.”

He stood at his kitchen sink watching Flores and a friend labor at night digging and pouring concrete not more than 100 feet away.

The neighbor told The Daily Beast the man he saw, who days later would be identified as Flores, and an unknown “young man with dark hair” took turns shoveling and wheelbarrowing to create a gaping four-foot-deep hole in the recesses of Susan Flores’s backyard.

“The hole was about waist-deep, mid-thigh level, and stretching seven to eight feet long, four to six feet wide,” the witness, who requested anonymity, said.

They worked by a retaining wall at the rear of the backyard for almost five hours altogether during the late night.

“I’ve never seen these guys before,” he said. “And they’re digging in this woman’s yard at this time of the day, and the kind of digging they were doing plus the concrete just didn’t make sense.”

In the middle of the construction effort he says he saw both men grab from both ends and lug a rolled-up rug with something “heavy inside.”

“I’ll tell you as a 15-year floor layer I can take a whole room of carpet, roll it up like a burrito—we call it cockroaching—you throw it on your back and walk it upstairs,” he said. “Two people were needed to move this. So it was heavy.

“And that’s the thing I’m tripping on,” he added.

He said they began to backfill the hole with dug-up dirt and poured concrete to form a slab.

A week later when Flores’s mug was splashed on the local news, the neighbor realized who the digger was.

“I recognized Flores and I knew exactly what I saw.”

Schafer’s report prepared back in 2000 referred to another neighbor named Lauri Quinn who also shared her version of seeing “ongoing construction work in the backyard” of Susan Flores’s property and later “newly constructed concrete planters cut into the existing cement in the backyard.”

Flores himself even abruptly attempted to cut short an interview with San Luis Obispo County prosecutors to attend to a “concrete” project at 4 p.m. of June 19, 1996.

“I just have to go,” Flores told them.

When investigators asked where, he said “I have to clean up some stuff. Some concrete.” Asked where he needed to clean it, Flores said, “My mom’s house.”

Another critical piece of evidence pointing to Susan Flores’s property is a certain earring that was “misplaced” by San Luis Obispo deputies. A beaded turquoise earring was discovered by a renter of the residence named Mary Lassiter when she was washing her car in October 1996.

Lassiter and her husband Joseph were deposed during the family’s civil dispute against Flores. Joseph Lassiter said the earring he saw was “hooped with beads that hangs down” and had “red stuff” on it, according to the warrant. That red stuff, the warrant notes, “resembled blood.”

Somehow during the recovery of the soiled item “the earring… was misplaced by the [San Luis Obispo] deputies and has yet to be found,” Schafer’s report states.

On March 3, 1997, sheriff’s deputies returned to the Flores residence with dogs, who gravitated to the corner of the backyard, but made no alert to any human remains.

On March 4, 1997, a contractor named Gary Mann conducted multiple ground penetrating radar scans for the sheriff’s office on Susan Flores’s property on the second day of the initial search. But, according to Schafer’s report, sheriff’s deputies discounted the “cadaver dogs’ interest in a corner of the backyard” at the residence because they “believed, at the time, Paul Flores’ mother, Susan Flores, did not reside” there.

“Later investigation determined that, in fact, Susan Flores did reside at [redacted] at the time of Kristin Smart’s disappearance,” the report states.

Mann found “broken pieces of cement he understood were placed there by Ruben Flores [Paul’s father] and Paul Flores about the time Kristin Smart disappeared.”

Mann informed San Luis Obispo sheriff’s deputies of a “backfill of some kind and looks to be man made” and believes he “discovered some anomalies on the west side of the backyard” but told authorities “he was 80 to 90 percent sure that his conclusion that the anomaly he discovered were a natural excavation or erosion.”

Schaefer speculated Susan Flores may have consented to a second search of the property because Smart's remains might have been excavated, which would explain the broken pieces of concrete.

Mann maintains that the home was “unfinished business” the warrant states and that he was “troubled by stains on the west side of the house that showed dirt had once been piled against the house” and also by “splatters of dirt” on the wooden fencing four feet away from the house.

After Schafer produced his report in 2000, he submitted to the San Luis Sheriff’s Office in hopes it would be used to obtain a warrant to search Susan Flores’s property again.

“I forced the warrant on a skeptical police force. I was told that officers present did not want to pay to have the concrete repaired if the search turned up nothing. That was a lost opportunity,” he wrote in a 2007 email to the Smarts.

Back in 2014 retired Mammoth Lakes, California, police detective Paul Dostie had traveled to Arroyo Grande with Buster to search for Smart, fresh off their biggest find ever.

Marine First Lt. Alexander “Sandy” Bonnyman Jr. was killed fighting the Japanese in the Battle of Tarawa in 1943. Bonnyman was posthumously awarded the Medal of Honor, but his body was never recovered.

That was until Buster, the black Labrador from Mammoth Lakes, California, arrived on Tarawa on a mission teaming up with the POW-MIA group History Flight.

Buster prowled the almost 300-acre island’s crushed coral turf and had several alerts in a straight line indicating the possibility of a trench burial carved out by a bulldozer.

The site was excavated in 2015 after Buster found Bonnyman and 47 of his fellow missing-in-action comrades who were recovered and brought home to American soil.

Buster’s nose also found six airmen who went missing after their B-26 bomber was shot down in Allmuthen, Belgium, during the Battle of the Bulge.

The men were returned to the United States for identification and burial.

Buster and Dostie also found Lynsie Ekelund, who was buried deep in a Santa Clarita, California, construction site by her confessed killer, Christopher McAmis.

In summer 2014, Buster signaled twice that he had found someone while sniffing around the fence line separating a neighbor’s home from Susan Flores’s property.

Buster by this time was hobbling along—having lost his right hind leg to cancer—and going through the backyard of Flores’s neighbor, along the wooden fence line on top of a 5-foot-high cinder block retaining wall. Smart’s remains are believed to be buried in close proximity to that retaining wall, Dostie told David Smallwood, editor and publisher of independent newspaper The California Register, who tagged along to document the search and photograph the moment Buster alerted.

“There’s human decomposition in that backyard,” Dostie announced.

“Old Buster turned around and locked up like an old bird dog—just froze in his tracks,” Smallwood, a resident of nearby Grover Beach, remembers.

Dostie’s associate Dr. Arpad Vass is confident that Buster’s nose is right.

“I did soil analysis from that site,” Vass said. “So we have soil analysis to back up Buster.”

Vass is a forensic anthropologist at the University of Tennessee’s Law Enforcement Innovation Center (who was brought in to give expert testimony in the Casey Anthony trial).

Of the 10 grams of soil samples they collected after two different visits to neighboring homes around the block and analyzing them through gas chromatography mass spectrometry, Vass said he is confident in his findings.

“We collected the soil samples and ran them and I’m sure we found evidence of human decomposition,” he said, referring to chemical compounds such as carbon tetrachloride, benzene, and pentanal emitted by human decomposition.

“I want to make it very clear—I’m not saying Kristin is there,” Dotsie insisted. “But it’s never been resolved by the sheriff’s office and they’ve completely ignored it through three sheriffs including this one.

“When Buster alerted there why didn’t they get their dogs and run them to see if they obtained the same result? Why didn’t the FBI do the same?”

The San Luis Obispo Sheriff’s Office initially spoke to The Daily Beast about some of these precise questions about the viability of the mother’s backyard and to answer about their current and past investigation efforts.

On why they haven’t returned to Susan Flores’s property, sheriff’s spokesman Tony Cipolla said the search has run dry there.

“That area has been searched several times,” he said. “We’ve used infrared radar technology in order to search plus we had deputies there as well. And so that has been searched a couple of times and we did not—there was nothing of an evidentiary nature that we were able to discover there.

“Anybody can say ‘Oh, yeah, we think it’s there.’ That can’t be admitted in a court of law.”

Cipolla discounted Buster’s findings by saying the dog wasn’t certified.

But Buster has been certified in years past with the California Rescue Dog Association (CARDA), both as an avalanche and cadaver dog. Cipolla’s dismissive statement says nothing of Buster’s success in finding Marines and airmen lost 70 years ago.

“He’s been certified before,” Dostie said. “The only certification in California is search and rescue: finding a dead guy on the surface. There is no certification for grave detection. If there was Dr. Vass and I would be the only ones qualified to give such a certification.”

At least they could have before the 12-year-old cadaver dog passed away this February.

“We were playing in the front yard and he just collapsed,” Dostie said through tears, remembering how he held his head till he took his final breath.

To know once and for all whether Smart was buried beneath the concrete doesn’t require a jackhammer.

If Dostie and Vass could get a chance to return to Susan Flores’s backyard they could accomplish all they need to do by drilling a few holes.

“You don’t have to tear out of the entire concrete,” Vass said. “All you need to do is drill a hole down to the concrete, down to the ground below and plant it and take a soil sample.

“It’s hardly any cost,” Vass continued. “It’s very simple to do and it’s relatively nondestructive. Why no one does that is beyond me. It’s so frustrating.”

In the end it shouldn’t be about showmanship or who gets the credit.

“As law enforcement our primary job is the victims,” Dostie said. “We can speak for the dead by finding them. We are advocates for the victims and their families. That’s what we are and that’s how we view ourselves. That should be our primary goal and politics should not enter. But unfortunately it always does.”