but that changed on march 18th, shortly before margaret and scott's baby was due. walsh: scott purk was taking a bath, and he saw his wife walk past the door a couple of times. he said he got out of the bathtub about five minutes later and he observed that his wife had somehow tied a rope from the banister on the second floor and had hung herself. narrator: margaret died a short time later. and to compound an already unimaginable tragedy, the baby did not survive. metcalf: but the first thought was, "why would she do this, this close?" you know, she was within like two weeks of having the baby. so, you know, it just -- it really didn't make a whole lot of sense. narrator: everyone was shocked. what happened seemed so impulsive, especially with a baby on the way. even first responders and akron police were suspicious.

the detectives really thought there was more to it. the emts thought there was more to it. narrator: no one had answers -- not scott, not the family, not margaret's friends. it was left to the coroner to decide what had happened, and the fact that margaret had attempted suicide years earlier played into his ruling. mifflin: with all the information that the coroner was given, he looked at everything in totality and decided, "i'm gonna rule it a suicide." walsh: ultimately, the coroner ruled that it was a suicide, and the police were really, you know, kind of forced at that point to just stay with that. narrator: years -- decades, actually -- went by. margaret's family mourned, but refused to believe she killed herself. my mom would call once a year just to see if there's any way they could reopen it, and, unfortunately, with that ruling, the case was closed and they weren't allowed to do anything about it. narrator: in the years after margaret's death,

there was another series of crimes that seemingly had nothing to do with her, until police decided to take a closer look at who was committing those crimes and why. ♪

not all caitlin clark's are the same. caitlin clark, city planner. just like not all internet providers are the same, 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: after his wife's suicide in 1985, sc moved with his life. but tragedy's seemed to follow him. [ engine starts ] ♪ [ siren wails ] in march of 2009, police were called to a fire at the house scott shared with his new wife and their two teenage children in stow, ohio. leidel: when you first pull up, the house was absolutely destroyed. it was gone. it was unsavable. narrator: luckily, scott purk and his family escaped unharmed.

scott woke up around 3:00 in the morning to go to the bathroom, and that's when he discovered the fire. he alerted everyone, and they were able to get kids out of the house. narrator: veteran arson investigators soon realized why the house went up so fast. there was a trail of gas that was poured. you could see the pour pattern on the grass leading all the way to the house and around the foundation. narrator: since detective ken mifflin assumed he was dealing with an arson fire, he asked scott purk the obvious question -- "was there anyone who would want to harm him or his family?" and scott immediately volunteered a possibility. scott and his wife had an open relationship. they were swingers, and they had an interesting lifestyle, to say the least. mifflin: they openly date, even long-term-dating the same people within the marriage, and they're both comfortable with that.

they both have their own girlfriends and boyfriends and so forth. narrator: was it possible a boyfriend or a girlfriend from outside the marriage had attacked the family? that does open a door to the possibilities that there were other people that could be involved with this situation. narrator: as police explored this possibility, they also did a standard background check on scott purk, and that turned up more than a few surprises. scott was an ex-convict with an infamous reputation. he was known by local media as "the ninja burglar." he was arrested for committing at least 10 different burglaries or breaking into cars and homes and businesses. and he was pretending to be a ninja. leidel: he would dress up in dark clothing and then break into women's homes, single women. normally, he would take, you know, car keys, things like that, but he would take their underwear, typically,

as his trophies, i guess, for lack of a better term. narrator: this string of burglaries, for which scott served seven years in prison, happened just months after the suicide of his first wife, margaret. there was probably no connection to be made, but detective mifflin couldn't get over an unusual exchange he had with scott the night of the fire. mifflin: scott and i are having this conversation about his house literally burning down right in front of us, and scott says to me, just out of the blue, you know, that he was married back in the early '80s and his wife, his first wife, who was nine months pregnant, had hung herself, thereby killing her and her baby, their first child together. so, he just brought that up out of the blue. no reason for the conversation. i had no idea. nothing -- i didn't even know scott purk prior to first coming to the scene. narrator: detective mifflin didn't know what to make of this. neither did his fellow investigators. we found it very odd that scott purk's home is burning

and he just kind of blurts out, "by the way, my first wife killed herself when she was nine months pregnant." narrator: detective mifflin, a seasoned veteran with decades of investigative experience, later said this was one of the strangest moments of his career, so strange that he decided to look back into scott purk's past. and what he found unearthed secrets that were literally buried with the dead. ♪

narrator: detectives investigating the 2009 fire that burned scott purk's home to the ground found that wasn't his first brush with a nearly fatal fire. back in 1980, the home he lived in also caught fire. if something in your life happens one time,

that's exactly what it is. it's just an incident that happens. when it starts to happen more than one time and bad things happen as a consequence of that, it's a pattern. narrator: detectives discovered that in this most recent fire, scott took some highly suspicious precautions before the flames started. walsh: he had loaded up his minivan with all their important possessions. they had clothes in there, cds in there, but they also had things like photographs and a very old cookbook, some things that had some sentimental value that they wouldn't want to have burn up in a fire. narrator: all the evidence appear to indicate that scott set his own house on fire. but why? walsh: it was determined that he set the fire to his home because he was well over $200,000 in debt and he was hoping to get some type of insurance money

by burning down his house. narrator: in fact, one of the key pieces of evidence against scott was something he said to his wife while making the 911 call about the fire. he had moved his favorite possessions out of the house, but he forgot one -- the family pet, a ferret named tito. it's totally not something that individuals would talk about, typically, when your house is burning down. this was planned out. somebody was supposed to get this ferret out of the house, and that person failed to do their job and left the ferret behind. and, of course, it met its demise in that fire.

narrator: investigators prepared to arrest scott purk for arson, but they couldn't let go of scott's seemingly offhand comment about his first wife, margaret's, long-ago suicide, made for no apparent reason as his house burned to the ground. i think there were certainly a lot of family members that believed all along that scott did it. metcalf: you knew deep down inside she didn't kill herself, but, you know, you had to resign yourself to the fact that, "well, this is what it was ruled, you know, so that's how it sits." narrator: and it sat that way for more than 20 years, but now investigators were taking a fresh look at the case. could it be possible that, after all this time, they would finally discover how margaret purk really died? there were still things to be solved here, still things needed to be done, but we needed justice for margaret. narrator: investigators reopen the case.

in most murder investigations, the victim's body is a primary source of evidence, and this case was no exception. in september of 2011, investigators got a court order to exhume margaret purk's body. mifflin: you just never know how things are gonna turn out when someone has been deceased for, you know, almost 30 years. leidel: there was so much water in the actual vault where the casket was, and then once we got the casket back to the medical examiner's office, we weren't able to open the casket. they actually had to get some tools and come in and break open the casket. and then there was a lot of water inside the casket. narrator: but to the amazement of nearly everyone, the body was in remarkably good condition. pandey: the chemicals in the embalming fluids will preserve you. you may have some, like, mold or mildew,

but essentially the body remains, you know, intact. and the embalming fluid will delay the decomposition. i'm not saying it's not getting decomposed, but they will delay the decomposition. mifflin: we were able to, you know, examine all organs that were not really properly looked at during the first autopsy, so we were able to gather evidence in this case. narrator: while a second autopsy was conducted, scott purk was arrested on the arson charge. detectives took the occasion to update him about the investigation into his first wife's death. leidel: detective mifflin tells him, "oh, by the way, scott, we got a court order to exhume your first wife's body." and it's almost like a valve opened and drained all the color out of his face, and his air of arrogance was totally gone. it was that moment where he knew that, "i screwed up." ♪

narrator: the question before investigators was whether they could prove scott purk staged the suicide of his first wife, margaret. scott claimed she'd hanged herself by anchoring a rope on a stair banister and jumping from a second floor. investigators had photographs from margaret's first autopsy, conducted way back in 1985, and now they had her body, exhumed in 2011. so, how did she die? forensic pathologist dr. maneesha pandey is a consultant to this program.

pandey: in a hanging, usually what i would look for is a ligature to see, you know, how the neck is, what kind of ligature has been used. and what is a ligature? it's anything which is used to compress your neck. narrator: a hanging will usually create a v-mark at the back of the neck because the pressure is coming from below, from the victim's weight. it goes upwards and goes up behind the ears and then comes up to the back of the head in a v-shaped fashion, so it will come out like this because the noose is at that "v." narrator: but if someone is strangled, the mark looks different because the pressure usually comes from behind the victim. there's no v-shape. there's no angling up behind the ears, and it just goes around. and the ligature mark is going to be similar to all the -- you know, whatever ligature has been used. narrator: scott claimed that when he found margaret's body, the first thing he did was cut the rope from around her neck.

but amazingly, after her exhumation and despite all that time under ground, margaret's skin told an entirely different story. because the skin -- it's elastic, so it tends to hold the marks. you're not living. you're not healing. so, if there's no healing, the mark will remain permanently. narrator: the surfaces of most ropes are rough, a little grainy, but the marks on margaret's neck were smooth, leading to speculation that a belt might have been used. to test this theory, detectives set up a simulation with a rope, a belt, and clay to play the part of human skin. what we did was we put the clay under the cans and then we took the belts and then we put it over the clay and started squeezing the belt closed, like as if you were gonna strangle somebody. you could see the perfect indentation. leidel: the stitching from the belt

made the same impression on the clay that we saw on margaret's neck. and our "aha" moment was that he used a belt to strangle her. narrator: and now detectives got an explanation for the strange, previously unexplained mark across margaret's chest. this was most likely from a rope. margaret, just days from giving birth, weighed a lot more than scott. the evidence showed that, to get margaret in position to stage the suicide, scott wrapped a rope around her to drag her to the right spot. that would be the only explanation why that mark would have been on her chest. narrator: in january of 2014, scott purk was charged with felony murder and tampering with evidence. but the role of science in this case was far from over.

before the trial, prosecutors took a highly unusual step. they teamed with investigators to re-create and videotape the alleged suicide scene in the actual apartment where it happened. amazingly, the banister that scott claimed margaret hanged herself from was still in place. the owner of the apartment had indicated that no changes had been made in 30 years to those banisters. they were the original banisters. narrator: the banisters were made of soft pine wood. prosecutors used a mannequin of margaret's height and weight. the mannequin was thrown from the second floor, simulating margaret jumping to her death. this time, the rope made a deep indentation in the soft pine wood. walsh: what was discovered is that if a rope was used and somebody who weighed a couple hundred pounds was hanging off that banister, it would cause an indentation in the wood of the banister.

narrator: prior to this simulation, there were no marks, no indentations on any of the banisters, disproving scott purk's story of suicide. reporter: 52-year old scott purk is standing trial on charges that he killed margaret anne purk. narrator: in november of 2015, scott purk was found guilty of margaret's murder and tampering with evidence. he won't be eligible for parole until he's 87 years old. when the jury came back with their conviction, it was just like -- what a sendoff gift for my retirement. narrator: one question nags detectives and margaret's family -- why did scott do it? theories abound, and scott is staying silent. my personal opinion is i don't think scott was ready to be a father. i don't know if there's anybody that could ever figure him out,

no matter, you know, how much time they have to study him. narrator: perhaps the oddest part of a very odd case is that if scott had just kept his mouth shut, he probably never would have been caught. scott would have gotten away with what he had done had he not said what he did the day of his fire. you know, it was a challenge. he was throwing it out there, letting us know how smart he was. walsh: scott purk got what he deserved, even though it was 30 years later. he has been found guilty. he is guilty. he violently killed his wife, who was due to deliver their baby any day. it's a horrific crime, and we are extremely pleased that he was found guilty. ♪

narrator: up next, a police officer's life is forever changed by a young woman's murder. it's as if you live that scene over and over and over again. narrator: there's evidence found with the victim, but no technology to properly test it. the case stalls for nearly two decades until a new device designed for food safety finally exposes a killer. this was kind of like the nail in the coffin. it is the most amazing thing i've ever seen in my law-enforcement career. ♪ ♪ narrator: about two weeks before christmas in 1995, todd bonner, a patrolman in utah's wasatch county sheriff's office,

got the kind of call all policemen dread. a farmer found a corpse next to a river on his property. bonner: this was a body found nude. you knew deep down in the back of your mind that this was going to be a different type of a case. narrator: the victim, a female in her late teens, perhaps her early 20s, had been beaten to death and left along an isolated stretch of the provo river. bonner: the scene was very graphic. you knew that she had taken one heck of a beating. she had -- she had suffered quite a bit. ♪ narrator: no conventional murder weapon was found at the scene, but it didn't take long to figure out what had been used to kill this young woman. six bloody rocks were found near the body. bonner: the rocks ranged in different sizes. we did come across one. don't want to say it was a small rock, but it was small enough that you could grab hold of it with your hand, and it appeared to have a handprint or fingerprint.

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.