Can new info help solve the case of missing college student Kristin Smart?

Kristin Smart was a college freshman who vanished in 1996 after attending a party just off the campus of California Polytechnic State University, known as Cal Poly, in San Luis Obispo, California. Her remains have never been found. Police have had a suspect since early in the investigation, but no one has been charged with her disappearance.

The unsolved case is the subject of a recent podcast, "Your Own Backyard," that has drawn millions of listeners and focused renewed attention on this decades old case.

Since the release of the podcast, things seem to be heating up with recent searches of several homes, including one belonging to the prime suspect, Paul Flores.

Can new information solve the case?

"YOUR OWN BACKYARD" PODCAST EPISODE 1: It's a cold and cloudy winter afternoon in San Luis Obispo and I'm retracing missing Cal Poly student Kristin Smart's last known steps.

Chris Lambert | Podcaster: I'm just a naturally curious person and this case is something that I've wondered about for years.

Kristin Smart 19, a freshman at California Polytechnic State University had gone to a party on Friday, May 24 , 1996 -- and has not been seen since.

Carla Hoffman

Chris Lambert was just 8 years old when Kristin Smart vanished on her way home from a college party in San Luis Obispo, California.

Chris Lambert: I remember seeing it on the news … it was something scary and they were talking about it pretty regularly.

But 22 years later, when he tried to find the latest on the case, Lambert was astounded by what he did not find.

Chris Lambert: There had been no news stories, no official word about Kristin Smart for almost two years. … It wasn't being talked about. … And that was frustrating for me.

PODCAST | EPISODE 1: So how did I get here making a documentary about this case myself? I don't know. I just checked and I'm a musician and recording engineer.

Even though he'd never investigated anything before, Lambert quit his job to create a podcast about the case.

PODCAST | EPISODE 1: At least once a day I asked myself what are you doing?

Lambert began looking into what happened to Kristin, collecting articles and documents, chasing down leads and tracking down anyone with information.

Chris Lambert: I didn't know the scale. I didn't know how many people were gonna listen. … but I knew that I could try to do a small part.

PODCAST EPISODE 1: I googled Kristin Smart's name every few years…

Chris Lambert's podcast podcast caught the attention of millions of listeners and sparked new interest in this decades-old unsolved case of Kristin Smart

CBS News

He never expected it would be a hit, but his podcast caught the attention of millions of listeners and sparked new interest in this decades-old unsolved case.

Back in May 1996, Kristin Smart was finishing her freshman year at California Polytechnic State University – better known as Cal Poly. Her younger sister Lindsey says their mother urged Kristin to go there.

Lindsey Smart Stewart: "You should go to Cal Poly. They're known for being a really safe school."

And it was only 250 miles from Stockton, California, where she grew up with Lindsey and their brother Matt. Her parents, Denise and Stan were both educators who encouraged their kids' passions.

Ann-Marie Christian: She was who she was because of her parents, for sure.

Ann-Marie Christian: became friends with Kristin in elementary school.

Ann-Marie Christian: Her parents reminded me of my parents. Just very involved with their children. You know, at their sporting events, at their activities. A very close-knit family.

The Smart family. Clockwise from left, Kristin, Denise, Stan, Matt and Lindsey.

Carla Hoffman

Like the rest of the family, Kristin was an athlete. She loved swimming and skiing. But Lindsey says her sister was happiest when she was traveling.

Lindsey Smart Stewart: She had traveled the world before she even made it to college. By herself, which is pretty amazing.

She spent a summer in London, was an exchange student in Venezuela, and a lifeguard at a camp in Hawaii.

Lindsey Smart Stewart: She definitely, like, took advantage of life, seized the day … she was super ambitious and was determined you know, to find the next adventure. … to find the next challenge.

That turned out to be college. Like so many freshmen, Kristin struggled. Classes were difficult, she was trying to fit in, and she missed her family.

PODCAST EPISODE 1: Kristin broke down begging her mother to let her drop out and go somewhere else.

But every Sunday when she called her parents, they encouraged her to stick it out.

Denise Pearce | Longtime family friend: Things were gonna get better and, you know, and – and they did.

Friday, May 24, 1996, was the start of the Memorial Day weekend. Most students had taken off – but Kristin had stayed on campus. So had Margarita Campos, who lived in the next room in Muir Hall. They had become close friends despite their differences.

Margarita Campos: I was a little bit more introverted and inhibited and she was like, "no, we have to go out and we have to go like … live life." … And she was growing as an individual. She was pushing herself out of her comfort zone. … and I was like, "Noooo."

So, when they were invited to a party that Friday night, Kristin was excited to go.

Margarita Campos: Kristin was like, … "come on, let's go, let's go." And I was like, "nah, I have to study." … And so, she pulled me into this sort of like, "oh come on, let's socialize. And these girls are inviting us out. Let's go." And I was, like, "uh OK, fine."

Margarita Campos: But when we got to the house it was pretty dead too, it was really -- it was like a couple of roommates hanging out playing video games … And Kristin was, like oh gosh, there has to be something better than this.

The two girls walked to an area off campus where there were fraternities, sororities and residential housing for students. Margarita soon decided she'd had enough.

Jonathan Vigliotti | CBS News correspondent: You wanted to go home, and you were trying to find a way to break it to your friend.

Margarita Campos: That's exactly right.

They got to the parking lot of an apartment complex.

Margarita Campos: I was, like, "Kristin, I'm going to go back home. I'm going to go back to the dorms. You can go." And she's like, "please come with me. Please come with me." …I told her I didn't – I didn't want to go.

Kristin did not have a purse, money, her I.D. or even her keys. So before leaving, Margarita handed over her keys to get back into Muir Hall.

Margarita Campos: She was absolutely sober when I left her.

Margarita Campos: I'll never forget her shadow against the building, this apartment complex, just standing like kind of cross-armed with the long leg … And she was just kind of like looking at me like, [sighs] you're really walking away now, like you're really, you're leaving?

The next morning, Margarita waited to hear from Kristin.

Margarita Campos: I was expecting her to knock on my door and be, like, "Oh, Margarita, you missed a rager. And here's your key." … I knocked on her door, and I thought she was just sleeping, or she went out and about, you know?

It wasn't until Kristin's roommate returned to their dorm room, that Margarita realized Kristin never came home.

Jonathan Vigliotti: How did you know she hadn't been back?

Margarita Campos: Nothing had moved.

All of Kristin's personal belongings – including her purse, her money, her I.D. – were in the room exactly where she had left them.

Margarita Campos: I mean, she was gone. She was gone.

By the time they called the Cal Poly campus police, Kristin had been missing for more than 48 hours. But Margarita says, the police did not seem concerned.

Margarita Campos: We were, like, this is – this is serious…. We thought we're calling the police, like they know what to do. … And the campus police – they were, like, "are you sure she didn't go out of town?" It's, like, she has nothing on her. … How could she have gone out of town?

Jonathan Vigliotti: They thought she was off possibly having fun.

Margarita Campos: Oh, yeah.

But they could not have been more wrong.

Margarita Campos: To this day, like, I was like, why – why did I just let her go by herself? … I did have guilt about that. … But you have to understand, she was a really independent free spirit.

Kristin's mother, Denise Smart, spent Memorial Day weekend at a swim meet with her two younger kids. She was looking forward to hearing from Kristin that Sunday.

Jonathan Vigliotti: And that phone call never comes.

Denise Pearce: The phone call never comes.

Instead, on Monday, May 27, Denise Pearce says the Smarts got a call from Cal Poly's campus police asking if Kristin was with them.

Denise Pearce: Kristin hasn't come home … And we're not sure where she is … We don't know anything.

Two days after her daughter went missing, Denise Smart got a call from Cal Poly's campus police. They told her Kristin had not been seen all weekend and asked them if Kristin was with them.

Carla Hoffman

That's when Denise Smart learned her daughter had not been seen all weekend, and all her belongings were still in her dorm room.

Denise Pearce: She was becoming more and more alarmed, you know? She was – she was frantic … I don't understand this, you know? What's going on? … It is every parent's worst nightmare.

The Smarts say they tried to file a missing person's report with the local police but were told it was too early, and the FBI told them Cal Poly police were in charge. But as Chris Lambert learned, campus police did not act right away.

Chris Lambert: At that point I don't think they had ever dealt with a missing person, a possibly murdered person.

By the time Cal Poly police began investigating, Kristin had been gone for four days. As they soon learned, she had ended up at a party at an off-campus house.

Chris Lambert: It's mostly frat guys from the Kappa Chi fraternity. … I don't know if Kristin knew anybody there.

Chris Lambert is a CBS News consultant and he's pieced together what he learned from people who were there that night.

Chris Lambert: Kristin became incredibly intoxicated, whether she was drugged or whether she just had a lot to drink in a short amount of time … She ends up passed out on the lawn next door.

Podcaster Chris Lambert

CBS News

Lambert says Kristin could not stand on her own, so fellow student Cheryl Anderson – who was also at the party – began helping her back to campus. They were soon joined by another partygoer, Paul Flores.

Chris Lambert: As they describe it, Paul Flores just sort of appears out of nowhere. … and offers to help. … He gets his arm around her torso and her arm around his neck, and he's helping her walk.

Chris Lambert: Paul keeps stopping along the way and letting Cheryl Anderson know, you can go on ahead. I've got her. It's fine. … She didn't think that was OK. So, she slowed down and walked with them.

When they reached the turnoff to Cheryl's dorm, she says Flores tried to hug and kiss her. She left them only after he promised to take Kristin back to her dorm.

Chris Lambert: I don't think she ever imagined that Kristin would end up dead by the end of the night.

Jonathan Vigliotti [with Lambert outside of the the dorms]: Paul and Kristin then make their way here. What happens next?

Chris Lambert: So, if you believe Paul's story, he goes into his dorm room here. And he leaves her to walk up this walkway. Her dorm entrance is right over here.

Chris Lambert: I personally think that wherever Kristin went, Paul was there with her. … I don't think she went back to her dorm at all

Whatever happened in those early hours, one thing is indisputable: Kristin Smart has never been seen again.

Jonathan Vigliotti: She had just 40 yards to go … and yet she vanished.

Chris Lambert: That's the upsetting part about it, isn't it?

The investigation seemed to be hampered from the start by a series of missteps by campus police – beginning with their assumption that Kristin was off having fun and ignoring worried friends who said she was missing.

Chris Lambert: So much was lost in those first few days where if that very first phone call … was taken seriously … answers might have been uncovered the first week.

They also did not focus on Paul Flores immediately, waiting six days to formally interview him. Even worse – they never sealed his dorm room.

Jonathan Vigliotti: There was a lot of evidence that could have been gathered, that wasn't. Why?

Chris Lambert: I wish I knew why. … They did an interview with the Cal Poly Mustang Daily … and explained that they didn't think there was any evidence that a crime had taken place.

By the time they inspected Flores's room, Kristin had been gone for 16 days. School was over, so campus police found an empty room that had been sanitized by the university's cleaning crew. Any evidence that might have been there was long gone.

Denise Pearce: The investigation was completely botched by the campus police. There's no question about it.

And while they did not rush to investigate Flores, Kristin's family says campus police were very quick to judge her. Just days after she disappeared, an incident report seemed to imply that Kristin's behavior contributed to her disappearance.

Jonathan Vigliotti: There was a lot of focus on how Kristin … was drinking – what sounded a lot like victim shaming.

Lindsey Smart Stewart: Right. A hundred percent that was happening.

The report said:

PODCAST EPISODE 2 [LAMBERT READING REPORT] Smart does not have any close friends at Cal Poly. Smart appeared to be under the influence of alcohol on Friday night. Smart was talking with and socializing with several different males at the party.

But while campus police weren't doing much, Kristin's parents were doing whatever they could to find their daughter.

Chris Lambert: Kristin's father would come down and hike every trail he could find on the Central Coast. He'd go anywhere. He'd go through tunnels, under bridges, looking for his daughter and expecting best case scenario. … He's going to find her body, which is awful for a parent.

Early on, a small group of volunteers also looked for Kristin. But a massive search did not happen until she'd been gone for more than a month. That's when the campus police finally handed the investigation over to The San Luis Obispo Sheriff's Office … but they did not find Kristin.

Five months after Kristin Smart disappeared, Paul Flores was brought before a grand jury but no charges were ever filed.

David Middlecamp/The Tribune_Zuma Press

Four months after that futile search, Paul Flores was brought before a grand jury. Little is known since the proceedings are kept secret, but no charges were ever filed. Just weeks later, Kristin's frustrated parents contacted James Murphy, a local civil attorney.

James Murphy: It was just a sad phone call to have somebody say, our daughter disappeared … and we think she's the victim of foul play and we'd like to pursue the guy that we think is responsible.

Murphy and his wife, Garin Sinclair, agreed to take the case pro bono – promising to go after Paul Flores and put pressure on the sheriff's office.

James Murphy: We had to be the initiators. You would have thought it would have been the other way around.

Murphy immediately filed a wrongful death lawsuit against Flores in civil court.

James Murphy: And it says wrongful death and then … I put murder. … putting murder on the lawsuit was sending a message to Paul Flores and his family, that we believe that he killed Kristin and that we're coming for him.

But trying to get him hasn't been easy.

Lindsey Smart Stewart: It just amazes me the amount of evidence that's available, yet nothing has happened. … The day after my sister disappeared, Paul Flores had a black eye and scratches on him.

The Smart's attorney James Murphy, and his wife – and office manager – Garin Sinclair, have had Kristin's billboard in their front yard since late 1997.

James Murphy and Garin Sinclair look at the billboard that has been in their front yard for more than two decades. They believe they can prove Paul Flores is responsible for the disappearance of Kristin Smart.

CBS News

Jonathan Vigliotti: You look at Kristin Smart every day.

James Murphy: Every day. … It's just a motivator for me. …[emotional] I will go outside at nighttime and I'll look up at the full moon and I'll think that that kid's buried somewhere real close.

Murphy and Sinclair promised the Smarts the billboard will stay until their daughter is found.

James Murphy: I'd love to do anything to end their suffering.

Jonathan Vigliotti: And that weighs on you.

James Murphy: Yup.

Jonathan Vigliotti: Is there any doubt in your mind that Paul Flores is responsible for the disappearance of Kristin Smart?

Garin Sinclair: No.

James Murphy: No.

And Murphy and Sinclair believe they can prove it. They have not been able to proceed with the civil case while there's an ongoing criminal investigation, but that has not stopped them from following every lead and preparing for an eventual trial.

James Murphy: There has been no other suspect. … every piece of evidence points directly at Paul Flores.

Like his black eye, seen faintly in a mug shot taken by the Arroyo Grande Police – just by chance – two days after Kristin vanished. At the time, they did not know about a missing college student. They were after Paul Flores for an outstanding DUI warrant.

James Murphy: Having a black eye doesn't make you guilty of anything but if the person you were with disappeared from the planet … that's physical evidence.

Chris Lambert says, two days after that, when Flores was interviewed by campus police, they asked how he got his black eye as well as scratches on his hands and knees.

Chris Lambert: And he says he got a black eye playing basketball with his friends.

But one of those friends told police Flores already had the black eye when he arrived.

Chris Lambert: He told those friends he just woke up with the black eye.

When authorities later confronted him with the two stories, Flores admitted lying and offered a new explanation.

Chris Lambert: He actually hit his eye on his steering wheel in the middle of the night while changing his stereo. … So now you've got three different stories about how he got that black eye.

James Murphy: He lied to the police about everything.

Two days after Kristin Smart vanished, Paul Flores went to the Arroyo Grande Police Department because of an outstanding DUI warrant. In his mug shot, a black eye can faintly been seen. When asked about how he got the injury Flores told three different stories.

James Murphy

Flores claimed after walking Kristin back from the party, he went to his room in Santa Lucia Hall while she walked alone to her dorm. But cadaver dogs told a different story.

Just days after taking over the investigation, the San Luis Obispo Sheriff's Office brought several dogs trained to detect human remains, to the Cal Poly dorms.

James Murphy: They brought in the first dog and they'd had the dog go through the dorms.

There was no reaction until the dog reached Paul Flores's room.

James Murphy: Why is a dog that is trained to smell human remains alerting on, amazingly, Paul Flores's dorm room? … they let the dog in, the dog makes a beeline to the bed of Paul Flores.

Remember, Flores's room had been emptied and thoroughly cleaned. But remarkably, the same thing happened with three more dogs.

James Murphy: That suggests that something bad happened in Paul Flores's dorm room.

The sheriff's office still wasn't convinced they had enough evidence against Flores. But Murphy says there were other incidents that should have raised alarm bells about him with law enforcement from the very beginning.

James Murphy: Paul Flores had a reputation amongst the girls that knew him at Cal Poly as being a creeper that he was always trying to hit on women.

In fact, Cheryl Anderson, who trusted Flores to walk Kristin back to her dorm alone, told police that her friends called him "Chester the molester," because he was known for groping girls.

PODCAST EPISODE 2: So, with Cheryl's account alone, we have an unsettling picture of Paul …

Just five months before Kristin disappeared, San Luis Obispo Police received a call from a student living off campus.

Chris Lambert: There was a man climbing her trellis and trying to get inside her balcony, very intoxicated and refusing to leave. When they showed up, it was Paul Flores.

No charges were filed, but Lambert discovered Flores's troubles started at a young age. In high school he was known as a loner. Chris Lambert spoke with some women who knew Flores back then. They asked him not to use their names:

PODCAST EPISODE 2 | WOMAN #1: Well his nickname was "Scary Paul."

PODCAST EPISODE 2 | WOMAN #2: You wouldn't want to be alone in a room with him. You wouldn't let any of your friends be drunk around him. Those were kind of unspoken things.

And they told Lambert they weren't surprised when they heard about Flores's connection to Kristin's disappearance.

PODCAST EPISODE 2 | WOMAN #1: I wasn't surprised, but there's also that shock value of kind of "oh my god, I knew it!"

Although suspicion surrounded Flores almost from the beginning, any hopes for an arrest were dashed in May 1997 when then-Sheriff Ed Williams made an admission to the San Luis Obispo Telegraph: "We need Paul Flores to tell us what happened to Kristin Smart … so absent something from Mr. Flores, I don't see us completing this case."

Jonathan Vigliotti: How significant was that?

Chris Lambert: I think that might have been the biggest misstep that investigators have made to this day. To … declare to the public …if you stay quiet, you will get away with this.

And six months later, when Flores was deposed by James Murphy for the Smart's civil suit, he kept quiet

JAMES MURPHY: Would you state your full name for the record please.

PAUL FLORES: Paul Ruben Flores…

In 1997 when Paul Flores was deposed for the civil suit, the only thing he would confirm on tape was his name. He invoked the Fifth Amendment 27 times.

James Murphy

Chris Lambert: The only thing he would confirm on tape is that his name is Paul Flores.

JAMES MURPHY: What is your present residence address?

PAUL FLORES: On the advice of my attorney, I refuse to answer that question based on the fifth amendment of the United States Constitution.

Chris Lambert: Everything else, he took the Fifth Amendment. …He wouldn't answer a single thing.

JAMES MURPHY: In May of 96 were you a student at Cal Poly?

PAUL FLORES: On the advice of my attorney …

He invoked the fifth 27 times.

JAMES MURPHY: What is the name of your father?

PAUL FLORES: On the advice of my …

Chris Lambert … and it worked. … You just don't talk, and you get away with it.

Flores wasn't talking. But was there evidence possibly placing Kristin Smart at his mother's home?

James Murphy: Somebody found an earring that they say … was Kristin Smart's jewelry in the driveway.

An earring that appeared to match the necklace Kristin is wearing on the billboard.

When Kristin Smart disappeared, Paul Flores's parents – Susan and Ruben – were separated and living apart. Four months later, while attempting to reconcile, Susan rented out her house in Arroyo Grande.

Chris Lambert: A young couple moves into it with their kid. … The mother is washing her car in the driveway at one point

PODCAST EPISODE 3: Something shiny catches her eye next to the front driver side tire. A single woman's earring.

That mother, Mary Lassiter, described it to Chris Lambert.

PODCAST EPISODE 3 | MARY LASSITER: It was like a red thing and it was like a smudge-like fingerprinted look on the back, just red, like maroon, like old looking and the smudge that it was like half a fingerprint.

It was turned over to a detective with the San Luis Obispo Sheriff's Office, but Garin Sinclair says, the Smarts never knew it existed until the Lassiters were deposed in January 1997.

Garin Sinclair: He never once turned to the Smart family and said, hey, we have an earring, we'd like to show it to you to see if it matches any of your daughter's jewelry.

The Smarts then demanded to see it.

Chris Lambert: And that's when they're told that earring has been misplaced.

Jonathan Vigliotti: Misplaced?

Chris Lambert: It was never marked as evidence apparently.

Mary Lassiter says the earring she found in the driveway matched the necklace Kristin Smart is seen wearing on this billboard.

CBS News

But Mary Lassiter says the earring matched the necklace Kristin is seen wearing on the billboard.

James Murphy: If it was, in fact, a piece of jewelry that matched Kristin's jewelry, it would have been blockbuster evidence.

And might have connected Kristin to Susan Flores's house, says James Murphy.

James Murphy: There's no way to get evidence back once you've lost it.

Another frustration for the Smarts: at the time Kristin disappeared, investigators weren't aware that Paul Flores's parents were separated and living apart. So, they did not immediately get a warrant to search Susan Flores's home.

Even more difficult to understand was why they waited two months to search the family home where Paul Flores was living with his father, Ruben. And when they did …

Chris Lambert: They didn't bring cadaver dogs with them. They didn't bring a forensics team. … They didn't look at the Flores family's vehicles.

They might have found evidence in those vehicles. Paul Flores did not have a car on campus, so Murphy surmises he had to have had help.

James Murphy: And it's 2:30 and 3 o'clock in the morning at Cal Poly … this is not a – a location from which Paul alone could easily move a body without a vehicle.

But further investigation of the Flores's two trucks seemed impossible. In the months after Kristin's disappearance, one truck was traded in and the other was reported stolen.

But it's Susan Flores's concrete backyard that has gotten the most attention. It has the been the focus of widespread speculation for more than two decades – especially her planter boxes.

Chris Lambert: Around the time Kristin disappeared, they cut out planter boxes in the backyard, so they cut out big chunks of concrete and filled it in with soil. … In one of Paul's police interviews … he mentioned that he wanted to be let out of the interview because he needed to help clean up concrete at his mom's house … So, what was being done in Susan Flores's backyard in the weeks after Kristin went missing?

And then there's this disturbing story that Mary Lassiter told Chris Lambert.

PODCAST EPISODE 3 | MARY LASSITER: In the master bedroom, I'm hearing this "beep beep" every night at 4:20 in the morning.

Lassiter says it came from one of the planter boxes in the backyard.

Chris Lambert: She said it drove her crazy and she went out there many times in the middle of the night to try to find it with sticks, sticking down into the planter boxes down in the soil. … And after a few months of living there, the beeping stops.

Even more chilling, Chris Lambert discovered Kristin was working as a lifeguard at Cal Poly and her watch alarm went off every morning about that time.

Jonathan Vigliotti: What was Denise Smart's reaction when you told her about this beeping in Susan's backyard?

Chris Lambert: Shock

Susan's house was finally searched in March 1997 – nine months after Kristin disappeared – but nothing was found.

Chris Lambert: I think it's very possible that Kristin was at Susan Flores's house at some point early on. … I think that anybody reasonable would have moved her somewhere safer.

It would be three more years before the property was searched again.

Members of the San Luis Obispo County Sheriff's Department and FBI searched the grounds of the Susan Flores's home in Arroyo Grande on June 19, 2000, for any evidence that might shed light on the disappearance of Cal Poly student Kristin Smart.

David Middlecamp/The Tribune_Zuma Press

PODCAST EPISODE 4: At 8 a.m. on June 19th, 2000, a team of sheriff's investigators knocks on the front door of Susan Flores's East Branch Street home. With them is a group of FBI evidence response team members and a search warrant.

That warrant allowed them to dig up the backyard, but deputies chose not to excavate. Denise Pearce says that was a crushing blow for the Smart family.

Denise Pearce: To be almost there. To think that you're going to finally get some resolution, and then it doesn't happen the way it's supposed to. Devastating.

And there would be more disappointment in 2007, after the Smart's legal team searched a small portion of Susan Flores's backyard with ground penetrating radar and did not find any evidence.

Chris Lambert: They just have never given up and are never going to give up on their daughter.

Ruben Flores and his estranged wife Susan have always denied any role in Kristin Smart's disappearance.

JAMES MURPHY: Do you have any information as to where Kristin Smart's body is located?

SUSAN FLORES: [Long pause, grabs water bottle] Of course not.

JAMES MURPHY: Your husband have information as to where Kristin Smart's body is located?

SUSAN FLORES: No.

When they were deposed by James Murphy, they also insisted their son was not involved.

JAMES MURPHY: Does your son have any information as to where Kristin Smart's body is located?

SUSAN FLORES: Nope.

JAMES MURPHY: Has your son ever told you that he did not kill Kristin Smart?

RUBEN FLORES: [long pause] We never asked that question. We just, "do you know anything about it". He says "no."

Through the years, the Smarts have kept pressure on the Flores family. But the Flores's have fought back, suing the Smarts for intentionally inflicting emotional distress on them. Like the Smart's civil case, theirs is also on hold.

In the meantime, Paul Flores moved to Southern California, where he has bounced from job to job. But as Chris Lambert learned, Flores's pattern of behavior with women didn't stop.

Paul Flores may have wanted a fresh start in Southern California, but Chris Lambert says, he could not seem to break old habits.

Chris Lambert: Paul worked with a number of women that he made incredibly uncomfortable … girls who he tried to make a pass at sexually, girls that he tried to force to kiss him.

Some of those women – who did not want their real names used – told Lambert about their encounters with him.

PODCAST EPISODE 4: So, I walk him up to his sister's apartment, and all of a sudden, he just like picked me up, carried me inside, turned around and shut the apartment door, and locked it. So, I said, "you better turn some lights on right now and let me out or I'm going to scream." … so eventually he unlocked you know, the apartment door, and I left.

Lambert also interviewed a woman who dated Flores until, she says, he became physically and verbally abusive.

PODCAST EPISODE 4: And he had like a butter knife and he like held it to my neck. And I was screaming. And my roommate actually kicked down the door to make him stop.

But Paul Flores was never charged with any of these incidents. Back in San Luis Obispo, the Smarts, feeling ignored by the sheriff's office, continued a relentless campaign to get them to do more to find their daughter.

Jonathan Vigliotti: What toll over time did this have on … your parents?

Lindsey Smart Stewart: I think they're, like, carrying boulders on their back.

Then, in 2011, there was a new sheriff in town.

PODCAST EPISODE 5: if you were making a film about a new law enforcer who's coming to a small town to save the day, you'd probably cast Parkinson.

Sheriff Ian Parkinson promised the Smarts that solving Kristin's case would be a priority.

Ian Parkinson: I committed to them that I was going to go back to the beginning … and re-examine every piece of evidence that we had.

But Parkinson acknowledges it hasn't been easy.

Jonathan Vigliotti: Was this case, given the evidence that was lost early on, doomed from the very beginning?

Ian Parkinson: Yes. I guess the answer is yes. There was early mistakes made that you can't recover from … when you're missing those vital pieces.

Jonathan Vigliotti: Is this a case that takes a miracle to solve?

Ian Parkinson: I hope not.

He hired a full-time detective to work on cases that were cold or unsolved, and over the past nine years, Parkinson says, there have been a number of new searches.

Including one in September 2016. After getting a new lead, the sheriff's office – with help from the FBI – excavated the hillside near the Cal Poly "P," but they did not find Kristin's remains.

Ian Parkinson: We've done 96 different interviews … And … collected 258 pieces of additional evidence.

Remember the Flores's two trucks that disappeared shortly after Kristin went missing? In 2019, the sheriff's office recovered both of them.

Jonathan Vigliotti: Any evidence … that you can tell us about?

Ian Parkinson: I can tell you that, yes, there was some evidence. But I can't tell you what the evidence is. … We're still in the process of examining forensically some of the evidence using … state-of-the-art technology.

And earlier this year sheriff's investigators and FBI agents went back to search Susan Flores's house. At the same time, more investigators showed up at Paul's house, his father's house and even his sister's house.

Earlier this year sheriff's investigators and FBI agents went back to search Susan Flores's house, Paul's house, his father's house and even his sister's house.

KCOY

Jonathan Vigliotti: Are you hopeful that cops are moving in?

Chris Lambert: I've been hopeful the whole time. … Once I could see proof that they were moving forward … I thought, somebody is taking this seriously. … But how much time do you give them? … You've got to move, and you've got to do it now.

More than two decades after Kristin vanished, Parkinson says Paul Flores remains the only suspect in her disappearance.

Ian Parkinson: The question is, is what role did he play? … that becomes the — the challenge of solving and proving.

Chris Lambert: I don't think he intended to kill Kristin. ... I don't know if it was a struggle, if it was an accident … But I do believe that Paul tried to clean up that mess and make sure that he didn't get in trouble for it. … And it's been 24 years. … I think it's time to talk.

"48 Hours" thought the same thing and tried to get answers from Flores during an unscheduled interview outside his home.

CBS News correspondent Jonathan Vigliotti tried to get answers from Paul Flores during an unscheduled interview outside his home.

CBS News

JONATHAN VIGLIOTTI: Hi Paul. Good morning, I'm Jonathan Vigliotti with CBS News. Were you involved in the disappearance of Kristin Smart? Paul, can you tell us what happened that night between you and Kristin.

PAUL FLORES: Go f —- yourself.

JONATHAN VIGLIOTTI: Paul, aren't you fed up of not being able to share your side of the story? All the suspicion that has followed you for so many years.

PAUL FLORES: Private property …

JONATHAN VIGLIOTTI: Do you know where Kristin's body is? … Paul, what happened?

PAUL FLORES: [slams door to house].

Denise Pearce says her good friend Denise Smart won't rest until she has the answers and Kristin is found.

Denise Pearce: She once said to me, you know, early on, "I don't know what I would do if this went on for 20 years." You know, I'm like, "oh, you're so crazy" ... And here we are at 24 years. She has never given up. [Cries] … I'm just so hoping that there's gonna be some resolution real soon.

Earlier this year, Lindsey Smart Stewart came to a beautiful spot overlooking the Pacific Ocean, and home to Kristin's memorial.

A bench and memorial for Kristin Smart is located beautiful spot overlooking the Pacific Ocean,

CBS News

Lindsey Smart Stewart: So, we're at Kristin's lookout point. … my daughters decorated it with roses.

It's the first time that Lindsey has visited in 13 years.

Lindsey Smart Stewart: It feels good. I wouldn't be here if I wasn't this optimistic and this hopeful like in this moment.

Lindsey Smart Stewart: I feel like the clouds are clearing. … you don't ever stop thinking about 'em. … I think of her as a bright, warm light … we'll never forget her.

The Kristin Smart Campus Safety Act became California law in 1998. It requires campus and local police to have a joint plan to handle investigations of violent crime on campus.

The Smart family keeps the memory of their daughter alive through the Kristin Smart scholarship. Its goal is to help young women pursue their hopes, ambitions, and impact the world in the same way Kristin had hoped.

Produced by Lisa Freed. Greg Fisher and Michelle Fanucci are the development producers. Mike McHugh is the producer-editor. Ken Blum is the editor. Alicia Tejada is the field producer and Addison Briley is the associate producer. Lourdes Aguiar is the senior producer.