Dateline. Heres Dennis Murphy with the collector. Reporter if your travels take you to the ozarks in southwestern missouri, that splendid lake country, you maybe have bass or trout fishing on the mind. Or perhaps youre heading to branson to catch a few of the stage shows. But there was no tour guide that would have directed you to this modest home in springfield, missouri, and thats a shame because it was an old curiosity shop well worth seeing. Floor to ceiling collectibles. Valuable stuff everywhere the eye landed. But still every object just so. Think neat hoarders. Anything from coins to arrowheads to he had probably 10,000 to 15,000 books. Hes big into gold and silver, gems. Bayonets from world war i and just, all kinds of stuff that he, you know, a leg cannon. Reporter but did these collectors who had such a knack for finding treasure have a less discerning eye when it came to sizing up people . Did that go towards explaining the dreadful toll in that house that evening . I said, hes off in some way. I dont know. He could be a psychopath or something. I said it scares me. Reporter on april 30, 2014, did they fall prey to someone they believed could be trusted . I had to be lowered to the ground. And i started crying and screaming. Oh, not those oh, such good people. Why . Reporter springfield, missouri, is called the queen of the ozarks, a churchgoing, neighborly city of midsize with good colleges. Gary tyrrell grew up poor on a farm not far away and knew early on that his adult life would be all about education, teaching kids in his classrooms by day, the history book in his lap at night. He and his wife jan raised two kids, a girl and a boy who sadly died young of a brain cancer. Jan kept the house mainly and sold Avon Products part time. They lived and gardened in the same house for almost 25 years. They even designed it themselves. Life in missouri was good for the two. They loved each other very much. Reporter daughter jessica remembers how extraordinarily close her parents were, joined at the hip. If my mom went shopping, my dad took her. They gardened together. Talked on the phone, you know, several times a day if they were apart. They really did everything. Reporter so they really were for the ages, huh . Yes, yes. Reporter personalities . Gary was the fun, outgoing one. He was a very jolly man. You know, kind of like a santa claus. Reporter jan, a little more reserved. It took a little bit more to get to know her. And then once she warmed up to you, she was very alive. Reporter when gary retired as a beloved assistant School Superintendent, he suddenly had all the time in the world to visit civil war battlefields, scour flea markets and pore over his antique dealers catalogs. But there was a lucrative sideline to his obsession for memorabilia. And he was big into buying and selling gold and silver. Reporter garys brother, larry tyrrell. He constantly collected coins and bought gold and silver trinkets. Reporter and did pretty well at it . He did very well at it. Gary was a good businessman. Reporter the gold and silver went into one of five safes in the house. But the coins and artifacts, many of them museum quality, were out on display. He had a lot of rare pieces. A lot of indian jewelry that was very quality pieces that he loved. Reporter what was his most unusual piece, do you think . Probably be the walrus tusks that he owned. He had three of those. Reporter they were rare 19th century hand engraved scrimshaw. And each worth around 10,000. So how would he find these things . Im not really sure. They did go to flea markets and garage sales and things like that, but any time i would ask him, you know, where did you get this . He would say, oh, in my travels. Reporter in 2013, jason murray, became one of the family when he and jessica got engaged. He remembers the walrus tusks as well as all the other unusual items in the tyrrell home. It was one of those things where like there was so much stuff in the house and yet it was immaculate. Everything had a place. And he had so much stuff, it was like an offbeat museum. Reporter jessica and jason lived almost 300 miles away in oklahoma city. But jessica spoke with or texted her parents several times a day. But that all changed on may 1st. I had called my mom on my way to work, like i always do. And she didnt answer. So i thought, well, maybe shes in the bathroom. Maybe shes outside. And i called back, and i still didnt reach her. Reporter by noon, jessica says she still couldnt reach her. So she called the Springfield Police and asked them to go by the house. And when the officer did that, what did he report back to you . That nothing seemed out of place. They couldnt see anything inside the house. All the doors and were secure. Absolutely no signs of forced entry or that anything appeared to be out of place. Reporter the officer had no cause to force his way into the house and left. But jessica says she was still worried. So she and jason jumped in their car to make the fivehour drive to springfield. They arrived at the house around 7 00 p. M. As we were coming around the corner to the house, i hit the garage door button. And both of their cars were in the garage. Reporter and that was bad news for you . Yes. Reporter what did that imply . That there was something terribly wrong. Reporter jessica called 911, without ever going past the garage into the house. Two officers arrived within minutes. They entered the home. And then another officer arrived and then another and then another and then another. Reporter and youre waiting outside . And were waiting outside. Reporter no one said a word to jessica and jason. And then, they noticed police blocking off the area with crime scene tape. I kind of grabbed on to the officer and i said, what is going on . Why are they calling for crime scene tape . And he kind of, you know, held me and said, i dont know whats going on. All i know is there are two people in the house that are deceased. Chilling words outside the tyrrells house. But they were nothing compared to what investigators would find inside. When we come back it seems to be an element of personal anger, this close quarter killing of somebody with a weapon in your hand. It definitely seemed to be personal. The brutality involved. Now, wes of clothes cleaned in one wash. Has anybody seen my pants . I found em ellen put those on, dad lasts up to two times longer tide, number one rated. When you have type 2 diabetes, like me, hi, im dominique wilkins. Theres a moment of truth. And with victoza®, a better moment of proof. Victoza® lowers my a1c and blood sugar better than the leading branded pill, which didnt get me to my goal. 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Taking victoza® with a sulfonylurea or insulin may cause low blood sugar. The most common side effects are headache, nausea, diarrhea, and vomiting. Side effects can lead to dehydration, which may cause kidney problems. Nows the time for a better moment of proof. Ask your doctor about victoza®. As darkness closed in on springfield, missouri, the daughter whod asked local police to check on her parents, was now being told two bodies were found inside her parents home. They didnt identify them, but jessica says she knew it could only be her mom and dad. And i started crying and screaming because i knew it was it was my worst fear. Reporter her fiance, jason, was by her side, trying to console her. She was beyond upset. She kept saying, im sorry, mom. Im sorry mom. I had no details. I had no idea what happened. Im thinking this is horrible and also hoping its carbon monoxide. Reporter not benign but something explainable. Right, right. Reporter but inside officers quickly grasped the cold stomachchurning truth. Jan and garys deaths were not accidental. It was going to be a long investigation. Reporter detective neil mcamuss was one of the first detectives on the scene. That night he entered the home through the garage and saw gary first. We could see that there was a deceased male in the hallway of the home. Reporter his pants were pulled down. What did you make of that . We didnt know. The only thing that we could think of was hes trying to get away from somebody, that theyre grabbing hold of him. Reporter or was the killer rifling his pockets for something . A key, maybe . A combination . In garys office downstairs, the detective saw jan. She was on the ground. She was lying face down. But it was obviously that there was severe trauma to the back of her head. Reporter so was this a violent Home Invasion . Jan and gary had more than a half a Million Dollars worth of valuables in the house there for the grabbing, so a botched robbery was a likely scenario. And in the garage, police did find strange marks and scratches on a tornado shelter that was also used as a safe. It appeared that somebody had tried to pry the lock open. There were some marks that were by the lock on the door of the tornado shelter. Reporter they didnt get inside. It did not appear that they did, no. Reporter but that would suggest somebodys looking for something. Yes. Reporter but if robbery was the plan, the killer had left the oddball museum strangely intact. Nothing appeared tossed or out of place. And the nature of the killings gary was shot as well as beaten spoke volumes to the prosecutor assigned to the case, todd myers. It seems to be an element of personal anger in this thing, todd. This close quarter killing of somebody with a weapon in your hand. Yes, it definitely seemed to be a personaltype killing, just the brutality involved. Reporter investigators determined jan and gary were likely killed the night before. But search as they might for the murder weapons, the gun and the bludgeoning instrument, officers came up empty handed. But they did recover some unusual evidence. Around jans body there were small white flakes of a substance that were obviously either from the murder weapon or on the murderers body. There were similar flakes found by the wound to garys head. Reporter so they bagged them and sent them off for testing. And the crime scene techs recovered Something Else that could be a crucial piece of evidence, a discarded latex glove. So a latex glove on the floor jumped out at you. Totally out of place. And from talking with everybody, that there is no way that gary or jan would have left that glove there. It was right in the middle of the floor for everybody to see. Reporter did it belong to the victims or the killer . No one knew. So its collected. You dont know what it means. We dont know what it means. And it was collected. Sent to the Highway Patrol crime lab. Reporter they had no idea, no working theory yet of why the couple had been murdered. But they did have a sequence that made sense as to the order of deaths. It is hard to believe that gary is shot upstairs if jan is still fully functioning and mobile that she would not have called 911, would not have tried to intervene in some way. Speculation but common sense tells you shes the first victim. Shes the first victim. Yes. Reporter shes bludgeoned to death downstairs, gary arrives at some point later. Most likely he arrives either while that is ongoing or the killer is waiting for them. But yes, it appears that she would have been the first to have died. Reporter a big question early on for detectives was understanding their crime scene. How did the killer gain entry to the house . There were no signs of forced entry. Reporter windows havent been forced. The doors are all intact. How did the killer get in . There are only two ways the killer could have gotten in. One would be to have their own access device, whether its a key, a garage door opener, some way that would open the doors up. And then upon leaving, be able to lock it that way. Or, to have been let into the house by either gary or jan. Reporter it didnt appear to the cops to be a random Home Invasion but rather that the killer or killers had been someone the couple knew. Was it a person gary encountered in his antiquing travels . Or, terrible to think about it, was the perpetrator someone much closer to home . Was this all in the family . I was shocked. Really confused and baffled. Coming up who had a motive to kill the tyrrells . Investigators have at least one idea. Shes the person who could benefit here from this crime in terms of getting money. Shes the only child from parents that are very welltodo with a lot thats going to be left to her. When dateline continues. Create your own tour of italy is back starting at 12. 99, only at olive garden. Choose 3 of 9 of our favorite italian dishes to get everything you want, all on one plate. Plus unlimited salad and breadsticks. Because the best tour of italy is the one you create. Olive garden. Tthe whitenessmy wasnt there as much, my teeth didnt look as healthy as others. My dentist said that pronamel would help protect my teeth. Pronamel is giving me the confidence to know that im doing the right thing so its nice to know that it was as simple as that. Two dead. The wife beaten about the head downstairs. The husband shot twice upstairs. And Springfield Police had determined this was no random breakin gone wrong. Jan and gary tyrrells modest home was filled with valuable items. And yet at first glance nothing appeared to have been taken. An early supposition was their killer was likely someone close to them. And no one was closer than daughter jessica. She is the person who could benefit here from this crime in terms of getting money. She had the most to gain. Shes the only child who has parents that are very welltodo with a lot thats going to be left to her. Reporter so shes going to be questioned hard . Yes. Reporter so that night, detectives asked jessica and fiance jason down to the station to answer a few questions. The cops didnt let on they were talking to them not just as grieving relatives but also as potential suspects. Im obviously going to take a few notes, obviously, as were talking. So dont let that bother you. Reporter the interviewer withheld details about the crime scene. A standard investigative tactic to see if a subject knows more than they should. He even threw out a theory that wasnt true murder suicide. One of the things we have to look at is as to whether or not that one of them wouldve injured the other and then maybe themselves. Reporter jessica seemed to go with it. Do you think thats a possibility . My dad, since his mom died, has been super depressed and has made comments. And my mom called the doctors office, and i told her if he did if he said something stupid before again, that she needed to call the police. Like get the [ bleep ] away from him and call the police. Reporter and as they continued talking, police had another reason to be suspicious of the daughter. Shed driven five hours to check on her parents then didnt go inside the house. Wouldnt you wonder why she would do that . Yes. People sometimes that commit a crime or know a crime thats been committed, you know, they dont want to see the bodies in there so they call somebody else. Reporter detectives pressed the couple about their movements that day, what they did or did not do at the scene. Had they tampered with that tornado shelter in the garage. You guys didnt do anything to try to get inside . Oh, no, no, no, no. I mean i pushed my hand on the handle, it was locked and that was it. Reporter did you think that maybe are we looking at a situation here where we have to call a lawyer or be careful about what we say . I did, a little bit. Reporter but neither jason nor jessica asked for a lawyer and offered the detective more detail about what was in that tornado shelter that had been tampered with. The safe room was full of gold, and silver, and gold bars and i dont even know we actually dont know what alls in there. I mean he has books that are signed by president s. He has indian peace medals. Reporter for investigators, the entire interview was a test. How are you going to hold up . Are you going to give answers that we can go back and verify . Reporter you so intend to sweat them . Yes that was the detectives intent to the degree of just trying to make sure we get the truth. Reporter did they pass the tests . Detectives let them go but held on to jessicas car to test it for potential evidence. Why did they have reason to look in your car . I didnt really know. I assumed it was just because my car was there. Reporter now jessica had to call family and friends to tell them the news about her parents. Her uncle larry, her fathers brother, was at his law office when he got the call. She said mom and dad are gone. I said, what do you mean . Are they out of town . No, theyre deceased. I collapsed on the floor. Reporter you were a mess. I was a mess. The unknown was terrifying. Because i didnt know what had happened. Reporter but larry wasnt shocked or outraged to learn his niece was being looked at as a potential suspect. He was, after all, a criminal defense attorney and former prosecutor. I knew she had to be eliminated. I understood that. Due to the fact that she was the only child. She just had to be eliminated so that the case could move on. Reporter and the case did keep moving. But after a full week of investigating the daughter and fiance were not eliminated. Rather, detectives called them back to the station, this time interviewed separately. Jason first. Cops by now had figured out that the murders took place the night before the bodies were discovered. So where exactly were he and jessica then . We went to the pizza hut up on i dont know, probably 5 30 or Something Like that and came back home and stayed home. Reporter home five hours away in oklahoma city. You remember how you paid for the pizza hut . On my credit card. Reporter then right to the point. You have any reason to want to harm gary or jan . Did go into the house. Everything you telling me the truth . Absolutely. Reporter next jessica was in the chair answering questions about her relationship with her parents. Are they paying any of your bills . They pay my at t bill for my cell phone. Pay my car insurance. And i think thats it. Reporter im just going to ask. Did you have any ill feelings towards your folks . Anything that you would have been mad at them for, any reason to want to harm them or anything like that . No. My parents were my life. Reporter so better your financial situation or anything like that . No. I mean, if i needed something, all i had to do was call and ask. Reporter so youre a suspect. Right. Reporter in your parents double homicide . Yes. Reporter how do you deal with that . You havent even buried them yet. I wasnt really dealing with it. It was more just going through and saying i you know, i didnt do it. Reporter police asked both jessica and jason for dna samples, then set out to verify their alibis. My boss and i took a trip to oklahoma city, and we went to employers, spoke with fellow employees, with jessicas boss, and we went to the pizza hut to see if we could see some surveillance video. Reporter would it all check out or would an unexpected lead send the investigation in a new direction . This was a huge bingo moment. It was. Coming up garys best friend offers detectives some clues including texts he says he saw on garys phone. There were five in a row from a guy that he had taught in a class asking for money. Did someone need cash badly enough to kill . Before fibromyalgia, i kept on top of things. I was energetic. Then the chronic, widespread pain drained my energy. My doctor said moving more helps ease fibromyalgia pain. He also prescribed lyrica. Fibromyalgia is thought to be the result of overactive nerves. Lyrica is believed to calm these nerves. For some, lyrica can significantly relieve fibromyalgia pain and improve function, so i feel better. Lyrica may cause serious allergic reactions or suicidal thoughts or actions. Tell your doctor right away if you have these, new or worsening depression, or unusual changes in mood or behavior. 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On an early spring saturday in may, 2014, the very day Jessica Tyrrell had planned to go Wedding Dress shopping with her mother, she was instead burying both her parents. I basically just cried, and was constantly ill. What she was going through at that point is just unfathomable. I mean, she is just broken at this point. Reporter the Funeral Service was held at a high school in the Mountain GroveSchool District where gary worked for 30 years. Nancy littrell was a school board secretary. Just so hard to believe that something so bad could happen in springfield and double unbelief that its somebody you know. My heart has just gone out for poor jessica. Reporter the outpouring of love and support was a huge comfort to jessica at a time when she needed it most. Word had gotten out that cops were looking at her. Yeah, lots of rumors that i did it. Reporter thats tough to go out every day and say, i didnt kill my parents. Right. And it got very tiring to hear, you know, someone say, well, you need to look at the daughter. She did it. She has the most to gain. Reporter and they did take a hard look. Yes, they did. Reporter they think the daughter has killed them in order to get the money that she was in cahoots with her fiance. Isnt that awful . Reporter you might not have believed it or your circle of people didnt believe it or knew my circle my circle was not believing that. Reporter and behind the scenes, police and prosecutors had come to the same conclusion jessica and jason were innocent. Everything that jessica and jason were telling the police, the police were able to corroborate and verify. And they went through everything. They went through the phone records. The alibi was checked out top to bottom. It was. Reporter and when the dna results came back on the latex glove, neither of them was a match. The dna belonged to an unknown male. Was that a relief for you . Yes, i mean, we knew we didnt do it, so, i mean, it was like okay now you need to find who did it. Reporter the couple felt they could help their investigation with their own amateur sleuthing. For instance when jason went back to the house for the first time, he noticed something was missing. There was a display of little ivory pieces and multiple walrus tusks that are engraved art type things. They had been moved. Reporter walrus tusk, are we talking about like so . The big one was about yea big. The larger one wasnt where it was supposed to be. And the other wasnt there at all. Reporter jason told police that one of garys prized tusks could be the murder weapon. The source of those mysterious white flakes. Jessica noticed someone had been at her dads desk where he sorted coins. He kept them around his desk in coffee cans and bags, and he would be sorting them or organizing them. Reporter and a container with what would have looked like loose parking meter change was missing. Its actual value around 20,000 according to her dads records. The killer would have known the real value only if he moved in the same antique circles as gary, at least thats what the brother suspected. Perhaps gary went to buy some gold or silver and someone had set him up and had someone follow him home and got the drop on him or jan. And had robbed him and killed him. Reporter sounds very plausible. That was a big worry i had. Reporter but as they dug into garys business dealings, no potential suspects emerged. Few people had any idea how wealthy they really were. They did not show that type of wealth to people. It was always kept very quiet. The people that he would interact with, as far as selling the gold, were always very reputable type people. Reporter and because there was no forced entry to the home, larry offered up the very limited list of people who had access to the house. A handful of local contractors. I assume you were asking the garden guy and the cabinetmaker, whoever might have been in the house from larrys list of people to give dna . Right. Reporter at the same time officers were reaching out to others in the couples inner circle. Garys closest friend was mark porter, a married father of two and a prominent guy around town and a former School Superintendent. For us its just a wise thing to do. He was handsome. He looked good. He dressed good. When he first came to the district he drove a jaguar. Reporter nancy worked with both gary and mark. And they seemed to get along really well. Worked well together. I thought they were friends at school and off of school. Reporter so mark went down do the Police Station to talk with investigators. All right. Mr. Porter. Its mark, correct . Yeah. Do you mind if i call you mark . No. I just want to kind of touch base with you and talk about how you know them, how long youve known them. Ive known gary since probably maybe 15, 20 years. He was my assistant superintendent. I was the superintendent. Reporter mark knew a lot about garys coin business. He had started dabbling in it as well. He told detectives details that suggested a fellow collector could have targeted the tyrrells. Hes got people all over missouri that collect for him. And i know he goes to hotels and meets people and he runs ads in the paper. Reporter according to mark gary set up one of those meetings around the time of his death and it involved a lot of money. He was actually going to sell 50,000 of gold for cash. It was actually a buyer who was going to give him 50,000 in cash, thats all i know. Reporter he also mentioned Text Messages hed seen on garys phone from some other guy. Gary asked me to read him some of the Text Messages. There were five in a row from a guy that he taught in a class that was asking for money. Okay. And i have no idea you dont remember, was there a name attached to the text . Or a number . I cant remember. Reporter and remember, gary was shot as well as beaten. Could it have been with one of his own guns . Gary has guns everywhere. Gary has guns in every drawer of the house, i think. I mean, he likes his guns. He loves guns. Reporter but then mark gave detectives a detail that took them completely by surprise. He was supposed to meet me, actually, at 8 00 on wednesday, and didnt show. Reporter wednesday, the night of the murders. It was the first police were hearing of gary having plans that night. What else did the best friend know . Coming up mark gives a detailed account, one that troubles investigators. There were several things about that story that raised some questions. And then, larrys brother reveals who he thinks had a motive for murder. I know he had some sort of bad financial issue. With 100 nutrition, 0 fillers, always real meat 1. Lifelong smart nutrition. Its all in one. Purina one. If you a dry mouth can be ations common side effect. Thats why theres biotene. 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Who do you talk to for military advice right now . Im Hillary Clinton and i approved this message. Well, i watch the shows. I mean i really see a lot of great you know, when you watch your show and all of the other shows. While donald trump watched tv, as secretary of state, Hillary Clinton negotiated a cease fire in gaza. A reduction in nuclear weapons. Took on vladimir putin. And stood up against the trafficking of human beings. A steady leader in an unsteady world. Springfield police were talking to garys best friend mark porter who suggested plenty of theories about why gary was killed. He said garys money was cat nip for all kinds of folks. People knew they had money were always asking for it. Reporter then mark revealed something detectives didnt know. He and gary had plans to meet at mcdonalds on the night of the murders. How long do you think you waited on him . I waited probably a good i got there probably 7 45, probably 45 minutes. Okay. Reporter so the friend said he drove across town to stop by garys house. I went back to the house, knocked on the door. Nothing. Didnt answer. So i thought maybe they were gone or left. Because hell leave. Hell go and say, oh, man, i forgot, my bad. Im in kansas city. So i had no clue. Reporter mark told detectives that gary had stood him up before. No big deal. So he went back to his office at ibm to do some work. Now there were several things about that story that raised some questions. Reporter like . Like why would you wait 45 minutes for someone and not pick up your phone and give them a call and say, hey reporter whats up . Whats up . Did you forget . Reporter but what seemed really strange was that mark porter had just admitted to going to the house the night of the murders with a story that just didnt ring true. Why drive across town if he wasnt all that concerned about his friend missing dinner . So he drives a few miles across town to go knock on the door when his office is across the street, when it doesnt appear that gary is showing up. Reporter so he puts himself at the house, sort of a benign explanation. Yes. Reporter inside the Interview Room the detectives decided it was time for a break. Give me a couple seconds. Ill go back there and see if theres anything else. Can i get you anything, coke are water . Reporter trying to make sense of it all including this bit of information. Garys brother had told police that not long ago mark asked gary for a loan, put the request in writing, not just a little bit till payday but an eye popping 250,000. Thats the kind of money if you can get it out of your house as a second mortgage maybe youre lucky. Right. Reporter what did your father make of it . Did he consider it even for a heartbeat . No, not at all. When he was talking to us about it, he was kind of laughing. He said, you know, i dont know where he thinks i would have this kind of money. Reporter strange since not only would mark, garys former boss, have had a nice pension as a former School Superintendent, he was currently earning a sixfigure salary at ibm. Brother larry had suggested mark might have a gambling problem. I knew he had some sort of bad financial issue. Reporter when the detective came back to the room, the tone of the interview had changed completely. Have you ever had to ask gary for money yourself . No, only for only in trade or buying. Reporter suddenly mark porter was in the hot seat. So if i was getting information from somebody who told me that maybe you had a large gambling debt. I do not have a large gambling debt. That you asked gary for maybe some assistance. No. Would that be false . Thats not true. Reporter he denied asking for the loan, said the only time he discussed large sums of money with gary was about a real estate deal. Because hes always looking for investment, whatever. Reporter then detectives asked him the question theyve asked everyone else. Would he offer up a dna sample. I have like a cheek swab that ill ask if you are fine ill do that today. No, im going to wait. Any particular reason . I dont know. I dont know the legalities. I dont want to do something then my attorneys say i shouldnt have done that. Why would you not give us a dna sample . Reporter its your best friend. Your best friend. Were doing everything we can to find who brutally murdered your best friend and youre telling us that youre not sure youre going to give us a dna sample. Reporter the refusal wasnt evidence of marks guilt, so police let him go, but the investigation suddenly shifted away from the workers at the tyrrell home and toward mark porter. Some detectives hit the pavement to check out his alibi while others continued mining over avenues for leads. One cop thought to check a local database of pawn shops to see if any of the missing items from the house had been recently sold. That search them them here to r k coins. Tell us how your business ended up being very important in a Murder Investigation in spring field. Yes, sir. Reporter it was two days after jan and gary were killed when teddy ellington was working behind his desk and a guy with a tub of coins walked in. Reporter what were you seeing in him . Was he okay . He looked like any average guy to me. Nothing actually stood out about him at all. Reporter he had piles of dimes, quarters, 50 cent pieces. When you added up the face value of that stack of money, what was it worth . He had 1210 in face money. Reporter but the meltdown value of the metal itself was can worth what . I paid him 18,351. Reporter 18,351. A lot of money. And not far off the value of the coins jessica reported missing from her parents home. When he walked in and stacked his coins, your security cameras caught it all . Sure did. Reporter so who was it . Coming up how a mcdonalds coffee cup was about to blow the case wide open. Did your dashboard just light up when you hear that . Cant describe the emotion of it. Finally a Family Learning the truth. I remember falling to the floor. Tresiba® provides powerful a1c reduction. Releases slow and steady. Works like your bodys insulin. When my schedule changes. I want something that delivers. Tresiba® ready i can take tresiba® any time of day. So if i miss or delay a dose, i take it when i remember, as long as theres at least 8 hours between doses. Once in use, it lasts 8 weeks without refrigeration. Twice as long as lantus®, which lasts 4 weeks. Tresiba® is used to control high blood sugar in adults with diabetes. Dont use tresiba® to treat diabetic ketoacidosis, during episodes of low blood sugar, or if you are allergic to any of its ingredients. 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Detectives finally had a major break in the investigation. Silver coins worth around the same amount as the ones taken from the tyrrell home had turned up in a local coin shop. Surveillance cameras caught the transaction on video. The man certainly looked familiar but if there was any doubt he left a copy of his i. D. Mark porter. Yes. Reporter mark edward porter. This is a real license. This is the real guy. Thats him. Reporter but selling a load of coins didnt prove mark porter was guilty of murder. Remember mark also had an interest in the coin business. The best explanation for that was just simply that these were coins that mark porter had, it was just a coincidence that they happened to be sold the day after the tyrrells were killed. Reporter still for police, the friend, ibm executive, retired School Superintendent and by all appearances a pillar of the community, was now a prime suspect in the murders of jan and gary tyrrell. I never did like the guy. I never did trust him. I thought he was something of a fake. Reporter garys brother larry always had a bad feeling about mark. And he was convinced if mark was the killer, the motive was money. I felt that he was befriending and recruiting and grooming my brother to gain access to his money. I think over a period of time he saw jan as an obstacle. Reporter when jessica heard detectives were looking at mark, she wasnt surprised. He didnt show up at the funeral. Reporter conspicuous in his absence . Or am i making too much of his nonappearance . I think it was pretty obvious that there was something going on. Reporter and his former secretary said she hated working for mark porter. Ended up quitting her job to get away from him. I said hes off in some way. I dont know. He could be a psychopath or something, i said, it scares me. Reporter you used that word . I did. Reporter but what bothered police was his lack of cooperation. He wouldnt give dna. He wouldnt take a polygraph. Reporter add to that the suspicious pawn shop transaction and the story about stopping by the tyrrell house on the night of the murders and a talk with marks wife about the night of the killings only made them more certain. She had talked about making a couple phone calls to mark, and that she couldnt get hold of him and she didnt know where he was or what he was doing. Reporter but police still needed physical evidence, a dna sample to match to that latex glove found at the scene. So they hatched a plan to get one. You start tailing mark porter . Yes. Reporter cars outside the house . Yes, we had undercover officers that were constantly doing surveillance for weeks and weeks and weeks to try and somehow obtain a dna sample from him. Reporter but nabbing a sample proved more difficult than expected. In all those weeks, officers continued to come up empty. They watched him eat his lunch. They watched him get a togo cup. And they were all excited because they thought they were going to be able to get the straw hed been drinking his drink with only to see him pick the straw up and put it into his togo cup and leave with the straw. Reporter so he knew that you guys had eyes on him . Its difficult to know what he knew at that time. Reporter then three months after the murders, an undercover officer followed mark into an Automobile Oil change shop. Goes inside, marks got a coffee cup that hed gotten from mcdonalds. Hes drinking from the cup. He strikes up a conversation, a casual conversation. Reporter the suspect and the undercover cop. The suspect and the undercover cop. Obviously mark has no clue whats going on. As hes speaking with him, marks car gets done and he gets up and leaves and leaves behind the coffee cup. Reporter police had their sample. And in less than 24 hours, they had the results. Its confirmed. Its a match. The same dna from the coffee cup is the dna from the latex glove. Reporter does your dashboard just light up when you hear that . Cant even describe the emotion of it that were going to be able to hopefully bring some resolution to the tyrrell family. Reporter two weeks later armed with search warrants, detectives arrested mark porter at his office. How do you take that . You got the wrong guy . This cant be . Absolutely not. He said okay and turned around and put his hands behind his back. That was it, the only words he said. Reporter jessica was at work when she got the call. Two of my very good friends were with me. He said hes been arrested. And i remember falling to the floor, and just being so overwhelmed with relief that he was finally caught. Reporter even the former secretary who didnt like him was horrified. I couldnt believe it. I mean, oh. I thought, no. Reporter investigators went back to marks wife and told her that her husbands own story put him at the scene of the crime. You really need to help us out here. But when does mark say he was there . The time they were killed. No. Yes, maam. Yes, maam. Okay. Still circumstantial. Reporter and thats exactly what mark porters defense attorney seemed ready to argue. Mark hired one of the best to plead his case. He has a spotless record. Five College Degrees and has an outstanding past of good reputation. Reporter at a bond hearing, the defense revealed its strategy. They would argue that there was nothing suspicious about marks dna inside his best friends house. He was a regular visitor to the house, porter. He would get with gary and theyd put on their gloves and handle the old coins and the objects and thats why the glove is there. Jurors, its benign. Do you think that works as an argument in the real world of courtroom drama . Potentially yes. Reporter but what about that suspicious coin sale . Well, there was no way to know for sure the coins had come from garys house. And as for the assumption that mark porter was a compulsive gambler hopelessly in debt. You had to wonder if he got behind with a bookie or the mob. Did he owe money to some heavy people . That was a theory that we frequently talked about. There was never any evidence that we found that led to that. Reporter so the case of potential Death Penalty was not airtight. And when mark hired new attorneys who asked to talk about a plea deal, the prosecution was willing to listen. What are we willing to risk . To try to get the Death Penalty. Can we achieve what we need to achieve without the risk of going to trial . Reporter could have walked. Theres a chance of a hung jury and you have to do it all again. Theres a chance they come back on a lesser crime. Reporter both sides agreed. Mark porter pleaded guilty to two counts of Second Degree murder and was sentenced to life in prison. No eligibility for parole until hes 82. Im still very shocked, very sad. I have a lot of relief that mr. Porters finally going to be behind bars for presumably the rest of his life. He has to live every day with what he did. Every day he has to think about what he did. And all of the lives he destroyed. Reporter youre saying he has to live his life in a kind of remorse, but you havent seen any sign that theres that remorse. Thats the only bad part. But he still has to sit there. Reporter today jessica is doing her best to move on. In february of 2015, she and jason finally got married. We got married on valentines day. While it was a great day, it was also very sad. My parents werent there. Reporter larry took his brothers place and walked her down the aisle. She asked me to give her away, and what should have been my brothers job. Reporter kind of bittersweet moment. Mmhmm, yeah, thats true. It was an honor to do it, but it didnt feel right. Reporter to keep her parents memory alive, jessica has set up a scholarship in their names. As for that offbeat museum of a home, its still there with a loving daughter as caretaker. I still feel them there. They loved that house. My mom built that house. I grew up there. And so i cant let that go. Thats all for this edition of dateline. Im lester holt. Thanks for joining us. Announcer jane lynch hosts six of her famous friends. You look good, though, and thats all that matters. Announcer for a night of games. Were gonna win announcer good times. Thats the best i can give you. [all screaming] hes the worst drawer ever. You just lost. Shoot announcer and the chance to send one lucky contestant home with. 25,000 simoleons announcer the famous folks tonight are. What is it with these people . What kind of rules are these . Youre rich and you go here. Its a boat. Announcer and on the other side. She keeps stopping. Dodo, dodododo whoa, this took a turn. Announcer its hollywood game night