narrator: the rocks told detectives straight away that they were dealing with what's known as a crime of opportunity. for whatever reason, whatever motivated that, he grabbed the nearest thing that he thought he could kill someone with and just beat her for a considerable period of time until she died. some rocks were as large as a small microwave that you might see on someone's kitchen counter -- very heavy, 50 to 70 pounds at least, were used to very angry, very brutal. narrator: the victim's clothes were gone. there was no identification. and besides the rocks, there were few clues at the scene. the crime looked to be sexually motivated. but the autopsy threw that into question. king: there was not evidence of a sexual assault. there was evidence of a sexual encounter. narrator: that encounter may have been consensual. dna was recovered from the victim's rape kit, but this was 1995, only eight years since dna was first used to convict someone.

most states, including utah, were years away from using dna. there was a lot of forensic technology that exists in the world that is either too expensive or too limited to be used by law enforcement on a day-to-day basis. narrator: was it possible the victim knew her killer? a strange clue found not far from the body made it seem likely. the only other thing that was found at the scene was a pair of black socks, and they were about maybe 10 feet away from her body, and they were just placed neatly on a rock. narrator: these socks weren't haphazardly discarded. they were folded so neatly that someone, either the killer or his victim, had taken time to do this. why? no one knew. it was just strange. ♪ narrator: despite the absence of identification, the victim had some distinctive tattoos.

images were released to local media. almost immediately, two men, a salt lake city cab driver and the victim's boyfriend, called police. gardner: he identified her as tracy marie beslanowitch, and that tracy was his girlfriend and that they had moved from spokane, washington, about five to six months prior to that to salt lake city. narrator: todd bonner placed a call to deliver the grim news to the victim's stepfather in washington state. and when he did, this already strange case got even stranger. tracy's stepfather said she couldn't be dead because he had just seen her. he told me that tracy beslanowitch lived a couple of doors down from him, and he went to check to make sure that she was there. i waited on the phone while he was checking, and came back and said, "you have the wrong person." what the hell was going on? ♪

♪ narrator: when a 17-year-old woman was found naked and beaten beyond recognition, local detectives were determined to fight for a victim who evidence showed had clearly tried to fight for herself. she put up one heck of a struggle, blocked a lot of blows with her fingers, a way that the hide had been ripped off of each one of her fingers. she struggled all the way through it. narrator: her boyfriend and a local cab driver

identified the victim as a young woman named tracy beslanowitch. but tracy's stepfather, who lived 700 miles away in washington state, told utah police their victim could not be tracy beslanowitch. bonner: when mr. beslanowitch told me that his daughter tracy was in spokane, i mean, it's just like, "oh, my gosh, what's going on here?" narrator: the answers soon became apparent. the victim in utah was using a false name, the name of her younger sister, tracy. the victim's real name was krystal beslanowitch, and she was a young woman with a troubled past. gardner: krystal was a prostitute. krystal would use the street name baby tracy or tracy. and we believe that she would do that to try and throw off police if she was arrested. narrator: krystal's boyfriend, chris, was her pimp. the two had been living and working together for years, and they recently moved to salt lake city.

krystal was the breadwinner in their relationship. ♪ narrator: it was a sordid, degrading life, one this young couple was desperate to escape. karen mathis, herself a former prostitute, worked the same streets as krystal. mathis: we didn't care about ourselves. how can you? we didn't know any better. i didn't know any better. why krystal came at such an early age? she's had something happen to her in her past. this is not something that we wake up one day and say, "we want to go do this." narrator: when detectives learn that krystal turned to prostitution because she had no other way to support herself, the case they were determined to solve became deeply personal. i could not comprehend having one of my own daughters going through this. you're not supposed to take things personal,

but i don't know how you don't take it personal one way or another. narrator: krystal and chris didn't have a lot of money. they didn't have a car. they stayed in a seedy motel in downtown salt lake city, and krystal worked her trade in a very small area of town. mathis: we worked all day long out there. you know, you had to call in and check in to your man and tell him how much money you had. and sometimes they'd say come home or they would take you out to dinner, or then they would tell you, "go back to work." that's how it was every day. ♪ bonner: she would never leave a seven-block radius. that was just her working area. narrator: this raised questions for detectives. if krystal only traveled on foot, how did her body end up nearly 50 miles away from downtown salt lake city? gardner: there's thoughts going through the investigator's mind

that maybe she was kidnapped and brought up here. or maybe she went along willingly. maybe this individual promised her money, more money, maybe promised her drugs or something else to get her to go this far away from salt lake. narrator: since krystal's boyfriend, chris, didn't have access to a car, police eliminated him as a suspect. now police question the cab driver who also identified krystal. his name was clarence stonehocker, and he was one of krystal's customers. bonner: clarence stonehocker stated that he knew this young lady, that her name was tracy, that he was a cab driver, that he would give her rides whenever she needed. narrator: stonehocker, 45 years old, was married and had children. he worked at a local high school and had no history of violence. he seemed to be, you know, stable, family man. not what we'd think of as a brutal killer. narrator: that is,

until detectives dug into his background. ♪

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don't settle. get real deal speed, reliability and power with xfinity. she shoots from here? that's kinda my thing. get the real deal with xfinity internet today, and get fast speeds and a reliable connection to all your devices in the home —even when everyone is online. narrator: krystal beslanowitch's murder was deeply disturbing to people on both sides of the law. mathis: krystal did not deserve to die like that. i don't care who we are, what we were doing at the time in our lives. we don't deserve to die like that. i don't blame her for what she was doing.

she knew what she had to do in order to stay alive. narrator: krystal had a lot of clients, but one, clarence stonehocker, a cab driver known to many local prostitutes, went to the top of the suspect list. a lot of cab drivers were friends with us. they saved us a lot of times. we would jump in the cab to get away from the police. [ chuckles ] so, yeah, that would happen. narrator: clarence told police his relationship with krystal went well beyond sex for money. clarence wanted to marry krystal. clarence loved krystal with all of his heart. if he couldn't have krystal, no one could. narrator: but krystal made her living selling sex. was it possible clarence became jealous and got violent? i believe that he was more obsessed and in love with her. i mean, when you make a statement of, "if i can't have her,

no one else is going to have her," that's a true obsession. that's more than being in love with someone. narrator: another clue that could possibly link clarence to the crime was the socks, something that had baffled investigators from the very first day. they were identified as being hers. narrator: someone had taken time to fold them neatly and place them near the scene. could krystal have done it? not likely. the evidence showed she was fighting for her life. but if the killer had done it, why? many of krystal's friends and clients had a possible answer. we know that krystal had one way in which she controlled her environment when she was working, and that was that she kept her socks on. and so whatever went on between them, she had kept her socks on during the sexual encounter. narrator: people who knew her said this habit never varied, and clarence, as a regular client, would almost certainly know about this. she wore her socks all the time,

even when she was doing tricks with a john. there was a lot of red flags with clarence. narrator: was it possible krystal's killer used the socks to toy with her before the murder, or as an exercise in humiliation afterward? gardner: i think that the socks were removed by the suspect. yes, i don't believe that she removed the socks at all, due to the fact that she liked to keep the socks on at all times. narrator: investigators attempted to match clarence to what little evidence they had. utah's state crime lab still wasn't testing for dna, but private labs were. we had to talk long and hard to sheriff kenny van wagoner at the time to try and obtain some extra money to get these rocks tested, because the only way to test for dna was through private organizations. we spent well over $15,000 out of our budget. narrator: in 2008, the murder weapons, the bloody rocks that had been sitting in storage since 1995, were sent to sorenson forensics, a private lab.

rocks might have a very rough and porous exterior, and they also might have a large surface area. when you're swabbing a rock, you're not really getting into all those crevices. narrator: this method gave detectives the breakthrough they'd been waiting for. a partial male genetic profile was recovered from one of the rocks. gardner: we were ecstatic. this was more than what we'd had in the past almost 15 years since the crime had taken place. narrator: as a partial profile, it wasn't of much use in the national codis database, but analysts could do a direct analysis against clarence stonehocker's dna. and when they did, they got a result that sent the case in a direction no one had anticipated. ♪

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narrator: when a partial dna profile was recovered from the rocks used to kill krystal beslanowitch, detectives were all but certain it would match their chief suspect, clarence stonehocker. i wanted him. i was convinced that clarence was the man that did this. i was totally excited. i was ecstatic.

i thought, "wow, you know, this is going to be our big break." narrator: the dna was compared to clarence's dna, and to the utter shock of investigators, it didn't match. it broke my heart. i was sure that it was him. at that point, i did not think that it would ever be solved. narrator: clarence was cleared and was never charged in connection with krystal's murder. but while the case came to a standstill, forensic technology kept moving forward. in 2010, investigators learned of a new piece of dna technology called m-vac that wasn't even designed to solve crimes. carlsen: the m-vac was originally created to collect microbiologic material, like pathogens, off of food surfaces. narrator: could a device used for food safety find krystal's killer? the m-vac developers thought so. it works as a wet vacuum collection system.

it's simply like a carpet cleaner. it sprays down a sterile solution, it applies vacuum, it creates turbulence, and that collects the dna that couldn't be collected before. jeskie: using an m-vac is preferable when you're trying to get dna from a rock, in that it's going to soak into those porous nooks and crannies of that rock and collect the dna that might be deposited there. narrator: amazingly, with this method, analysts were able to obtain more than 40 times the material needed for a standard dna profile. at about the same time, the utah state crime lab finally got on board with dna. analysts there tested the 15-year-old sample from krystal's rape kit. both samples, the one from the rape kit and the one from the murder weapons, were a match to a so-far unidentified man. the codis dna database found him in florida. it was like someone totally brand new.

we had no idea who this guy was. narrator: his name was joseph michael simpson. he was 46 years old. in the 1980s, he served time for killing someone in a jealous rage over a woman. he stabbed the man 13 times and left the knife in his body and ran away, and told law enforcement that the man must have fallen on the knife. narrator: simpson was paroled in april of 1995 and found work as an airport shuttle driver with a regular route that took him right past the area where krystal's body had been found. maybe he was on his way back to the airport when he noticed krystal on the side of the road walking to the convenience store. i truly believe that he knew krystal prior. she was comfortable with him. and so she trusted him to be able to get in the car. ♪ narrator: because the m-vac technology was so new and because the dna from the rocks was so old, investigators wanted to make sure their case against simpson was airtight.

to do that, they needed a fresh dna sample. so they trailed simpson, and one day saw him discard a cigaret butt. tests match dna from that butt to dna from the rocks, from krystal's rape kit, and from simpson's prior arrest. right now, you're under arrest. bonner: i get chills just thinking about it. can you reach back? i don't know how to describe it. ♪ it's like waiting for something that you didn't think would truly ever happen, and then it's handed to you on a silver platter. it was like... a little kid at christmas, i guess. narrator: prosecutors believe simpson frequented local prostitutes and that he and krystal had prior sexual encounters. on the night of the murder, he saw her walking along the street in downtown salt lake city. she knew him and got into his vehicle.

they drove to the farm outside of town. since his dna was found in her rape kit and there was no sign of rape, investigators believe the two had a consensual sexual encounter. after this, something -- no one knows what -- sent simpson into a homicidal rage. he grabbed rocks, the closest weapons at hand, and beat krystal to death. but he couldn't have guessed that, nearly 20 years later, the m-vac would recover tiny bits of his dna caught in the crevices of those rocks and expose him as krystal's killer. carlsen: when you have a new technology that can do things that prior technologies couldn't, one of the first places that always gets used is the hail mary case, the case that has sat for a long time and hasn't had any progress in it. and the krystal beslanowitch case is one of those cases. narrator: as for the socks being folded so near the site, to this day, simpson has refused to explain it.

just one more thing that makes no sense in an utterly senseless case. mathis: joseph has an anger problem with women. joseph has an anger problem, period. i don't know, but i know he hates women. narrator: in september of 2016, joseph simpson was found guilty of aggravated murder and was sentenced to life without parole. for todd bonner, who worked the case for most of his career, justice for krystal made it all worthwhile. for every officer that was involved with us through this whole thing, it was closure. it was closure to my wife because i'd go home and i would vent to her, you know, about different things or vent to my family one way or another. probably against the rules a little bit, but you do it. and krystal became part of my family, whether i liked it or not,

every day... she was there. narrator: and if a story this brutal can lead to something positive, at least one good thing came from this tragedy. karen mathis was so shocked by her friend's murder that she turned her life around. mathis: krystal took me off the streets. krystal showed me that i can live on. krystal will always live in me. there's not a day that goes by that i forget about her. i'm lucky. i'm blessed. so blessed. ♪ ♪ narrator: up next, the big day for a yale research scientist is fast approaching. she was due to be married in about five days. narrator: and then, she disappears.

is this a case of a runaway bride? a yale university graduate student who is supposed to get married this weekend has suddenly vanished. narrator: this image shows the last time she was seen on surveillance video. on that day, we saw annie going in. narrator: but she's never seen coming out. you don't get in or out without being captured on camera. narrator: people don't simply vanish. or do they? ♪ ♪ yale is one of the oldest and most-respected universities in america. founded in 1701, the campus is dotted with beautiful buildings designed by generations of noted architects. but few people would call the building known

as 10 amistad distinctive. in fact, it's designed not to attract attention. 10 amistad is very nondescript for reasons. it's a research facility. so, there are all types of highly confidential multi-million dollar research that is done from foundations and organizations from throughout the world. narrator: one of the amistad researchers was annie le, a 24-year-old doctoral student of great ambition and brain power. strollo: she didn't go out much. she had a very strict routine of going to work at the lab, her studies, and back home. [ beeps ] narrator: on the morning of tuesday, september 8, 2009, annie followed her usual routine. the building where she worked required people to log in using electronic keycard. her movement, after going into the building, she went into her lab, which was g13,