but for those rachael left behind-- you know, there's no true justice. it doesn't bring her back. is there a new chapter opening up for you, amber? it's just begun. because when i found out my mom was missing, i fought tooth and nail. so did ashley. that's what we did. and so at this point, it feels like the fight is over. the grieving process for me has just begun because there's nothing left to fight for. that's all for this edition of dateline. i'm craig melvin. thank you for watching. . i'm craig melvin. and i'm natalie morales. and this is "dateline." we're all shells of people walking around.

the happiness in our life has been taken from us. craig melvin: they were high school sweethearts rearing five strapping sons. it was a rowdy house. and our parents loved it. craig melvin: then that terrible night. a mother murdered. but as shock set in, leads poured in. witnesses reported strangers lurking, a car speeding through the neighborhood, and there were footprints out behind the house. i'm putting alarms on every door, because somebody's out there. craig melvin: but detectives? they decided the killer wasn't out there but inside the house. now with one of their own under arrest, the family was furious. you see these people? this is love. this is belief in this human being. please listen to us.

craig melvin: did investigators rush to judgment? do you have any idea beyond your own fevered imagination that that's what happened? you don't have a clue. i think that i do have a clue. craig melvin: was the real killer still out there? hello and welcome to dateline. an unexplained death can fray even the strongest family ties. but when tragedy struck the duenas household, grief pulled them closer. clues at the crime scene seemed to tell one story. but as investigators dug deeper, they wondered if this loving family had a killer in their midst. here's keith morrison with a killing in cottonwood.

keith morrison: on the afternoon of may 4, 2012 casey duenas walked out onto the field for the start of his very favorite thing. high school baseball. a doubleheader. spring was in its full glory here in northern california. his senior year was almost done. this was the place he loved, the game he loved. people sometimes talk about having premonitions of things. did you have anything like that at all? it was just another day. just another one of my countless baseball games. countless baseball games. keith morrison: wasn't of course. though no one knew it, as they wiled their way through a golden afternoon. redding, california, with its famous sundial bridge, its parks, its middle america feel. it's a whole different place, a different life

than the california whose reputation blares technicolor from the botoxed and tmz narcissism 600 miles to the south. drive a few minutes from redding, and you're on the ball diamond in a little place called cottonwood. here in the shadow of mighty mount shasta, an anchor, a constant. just like the people casey knew would be in the stands. so were they there? yeah. keith morrison: both of them? both there. always there? always there. never missed a game. keith morrison: his parents, mark and karen duenas. side by side by the dugout as always. you know, they were together since they were, what? 17 years old. they practically lived in each other's skin. exactly. keith morrison: his mother had brought the chocolate chip cookies she passed out to the players after every game. and for which she was justly famous. his father had made sure he finished work in time for the opening pitch.

what kind of parents were they? they were the best parents that you could ask for. keith morrison: this is jason, their eldest son. and here the photo of jason's graduation with his proud parents the day he became a fireman. they would do anything for us. and they did. keith morrison: mark and karen were from big mormon families. high school sweethearts who married as teenagers and watched their own brood quickly expand. all boys. jason, jacob, tyler, troy, and casey. boys bursting with testosterone. it was a rowdy house. we had football games inside the house. we were egged on by our parents and they loved it. keith morrison: karen was a full time mom. and once the boys were old enough, taught part time at nearby shasta college. for decades, mark got up at 2:00 am to drive for ups. just because it freed him to coach his son's teams come afternoon. and to spare his wife middle of the night disruption mark slept in a separate bedroom.

had for years. my dad treated her better than anybody could treat their wife. my mom was the queen. they lived simply. they live paycheck to paycheck. they never had a lot extra. keith morrison: son tyler. for them, it was all about family. yeah, always. keith morrison: and they all stayed as close as any family could be. when jason got married, he moved into the house right next door. helped celebrate mark and karen's silver wedding anniversary as they all did. by 2012, they were grandparents many times over. had been married nearly 33 years. one thing i always looked up to and loved about their relationship was that they still dated. keith morrison: tyler's wife tina. after that long, sometimes you can lose that. and i never saw them lose that. keith morrison: but change does come for everyone. and by 2012, in their early 50s, mark and karen

were making some changes. karen went back to school. nursing school. this was a plan that they'd talked about. it was the perfect situation. she got to stay home with the kids all growing up. and now she was ready to start her career. if you think about it, a pretty dang good plan. he worked his whole life. yeah. you know, he could start his own business while collecting a pension. and then she would start her career in nursing. keith morrison: not so easy, of course. nursing school is a tough thing. and not just for karen either. her brother joe and wife jackie. well her commitments changed. having grandma there when you need her or having mom there when you need her. she was going to have to study. and she was struggling with the classes. she felt like she should be doing better. but i remember a text that said i just got back from the er and got a chance to work with people finally. and i love it. and so she was on her way. she was really on her way. keith morrison: and so that may 4,

casey joined his parents at home after his ball game. then it being friday night, he and a friend went to see a movie. the avengers. it started at 9:15. and told my parents everything was fine. do you remember the last thing you said to your mother? she handed me a $20 bill. and i thanked her and hugged her and left. keith morrison: it was late when casey returned. and almost immediately fell asleep. and then what do you remember next? it literally felt like put my head on the pillow, and two seconds later, the door's opened. dad's at the door freaking out. keith morrison: and seconds later. the duenas family was about to discover that a perfectly ordinary evening had ended in tragedy. coming up. a dad devastated.

is one tragedy about to become two? yeah, i remember him coming in the door and just collapsing. falling on the floor. narrator: when dateline continues. herbal essences is a force of nature. made with supercharged botanical blends, our sulfate-free formulas deeply penetrate to boost hair health. without the salon naturals price tag. herbal essences. what are folks 60 and older learning these days? new perspectives! ♪♪ how to fix things. ♪♪ fun recip... (high pitched sound) (high pitched sound) (high pitched sound)

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already taken. get 20% off and free shipping on your first order at nuts. >> com the second inauguration of donald trump morning joe kicks off coverage. >> then at 10 a.m, rachel maddow and team will bring you key moments of the day, followed by analysis from our prime time anchors as the new term begins tomorrow, beginning at 6:00 on msnbc. >> breaking news a fast moving disaster in california. >> breaking news israel and hamas will enter a cease fire in the nation's capital, philadelphia. >> el paso, the palisades from >> el paso, the palisades from msnbc world headquarters. keith morrison: it was 12:30 am. now may 5, 2012. casey duenas is home from a movie and late dinner with friends, opened the front door,

unlocked as usual. and moved quietly down the little hallway toward his bedroom. had it not been so late, he might have stopped by his mother's room to say good night. but the house was dark. everyone asleep. or so it looked to an exhausted casey, who fell into bed and almost immediately into a deep sleep. and then, 25 minutes later. dad's at the door freaking out. go next door, go next door. go get jason. something's happened to your mom. go get jason, go get jason, go get jason. keith morrison: casey did as he was told, running next door to his oldest brother jason's house. while his father mark, beside himself, called for an ambulance. i can't, i have no idea. >> you have no idea what happened. you don't know where

she's bleeding from? she's bleeding from? >> no, i and jason woke up to the horror two ways at once. fire department alarm, brother alarm. i was asleep. as a volunteer firefighter, i have a pager. the pager went off. and i could hear casey coming up the stairs yelling at me in a panic. there's something wrong with mom. you got to come next door right now. did you have any sense of what it was? i had no idea what i was going to walk into. keith morrison: what he walked into was a nightmare beyond dreaming. there was his father in full blown panic. and lying on the floor in a puddle of blood was his mother. and the rookie firefighter for an instant, to his eternal regret, froze. if i would have come on that situation now, i would have immediately started cpr. there was a great deal of blood. so for somebody to live through that, that much blood,

i didn't think it was going to happen. i believe i just missed her last couple of breaths. keith morrison: minutes later, emts arrived and karen duenas was pronounced dead. the cause? multiple stab wounds, including a massive gash to her chest. not long after that, the young detective arrived, logan stonehouse. a year under his belt as an investigator, but this would be his first big homicide case as lead detective. and lo and behold. i didn't know what i was walking into until i saw a picture on the wall and realized whose house i was in. you knew these people. right? i did. well i went to high school with the second oldest son jacob. keith morrison: and here he found himself looking at the bloody body of jacob's mother karen. the lady everybody loved. the one who brought cookies to all the games at school. who could have done this? the detective took a look around the house. he and fellow officers fanned out around the neighborhood.

there were some footprints outside the property. right? logan stonehouse: there was. there was a wood fence that surrounds that piece of the property. and there's a back gate back there. and there was a little trail that led out to a canal area. keith morrison: and the first patrolman on the scene told them he had seen a car speeding away as he raced toward the duenas house. neighbors reported seeing two strangers nearby that evening. and here, in this crime scene video taken the next day, a screen on the window in karen's bedroom that looked suspiciously like it had been cut open. had intruders entered here? was anything disturbed around the house? no. actually the bedroom was pretty much intact there wasn't drawers taken open like someone had burglarized the place. also, even though the screen appeared to be cut, didn't look like anybody had actually gone in that way. and so the detective had some questions for the only man known to be in the house all evening.

the husband, of course. mark duenas. what was his story of what happened that night? he told us that he had been up with karen. they were watching a movie. and then once karen went to bed, he tried to stay up a little bit longer to watch the giants game. he was falling asleep during it so he decided to go to sleep himself. keith morrison: mark in his room, karen already down the hall, he said, in hers. the detective took mark to the major crimes unit, where mark, who had been awake more than 24 hours by now, finished the story himself. i'm in my room asleep. i hear crazy noise. and you know, you hear a cat sound like. it wasn't cats. it was a weird scream. talking? or-- no. i just heard some weird screaming type stuff. and then what did you do from there? i ran. i got up and i-- because i didn't want whatever was going on to wake up my wife. because i'm sensitive like that.

and i went to that door by the kitchen, opened it up, and looked it out there. i didn't see any cat. shut it. walked down the hallway. looked under, the lights were on. so i think she's up. open the door. and that's what i found her. keith morrison: the detectives questioned mark for more than three hours, had him change so they could keep his shorts and t-shirt for testing, then sent him home to his children. i remember him coming in the door and just collapsing. falling on the floor. we were really worried about him because he kept saying like his heart. and so we thought maybe he was having a heart attack. i mean, he was-- he was a mess. keith morrison: as the duenas family planned a funeral, their big extended family, including karen's brother joe and wife jackie, descended on cottonwood. i've never seen a person more broken. what was your perception of how he took it? he's taking it incredibly hard. he still does. keith morrison: and along with unbearable grief for

the family came anxiety. i live next door. i'm worried for my family and i'm putting alarms on every door because somebody's out there. keith morrison: but the police did not seem to think that. in fact, within a day or two, one of the detectives announced no need to worry about some unknown killer stalking the town. now why would he say that? craig melvin: coming up, investigators were about to hear a strange tale from none other than karen's husband. it scares me when i think about it. craig melvin: but what did his story mean? when dateline continues. yeah. >> frank dulcolax chewy fruit bites for fast and gentle constipation relief in as little as 30 minutes, making your good morning even better with

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>> com each week on my podcast, i'm joined by uniquely qualified guests who help me take a big picture look at the issues like representative jasmine crockett, late night host seth meyers, former attorney general eric holder, and many more. why is holder, and many more. why is this happening? listen now. keith morrison: they measured time in units of pain in little cottonwood, california during the surreal minutes and hours and days after karen duenas was murdered. the best way i can explain my mom is she was pure of heart is the best way to say it. keith morrison: the whole big family. karen's family, as well as mark's. parents, brothers, sisters, gathered to support each other and mourn and struggle with the question that hung in the air. who did this? but the word on the street was there was no question at all.

we immediately heard rumors, outlandish rumors. i don't know where you're getting this. keith morrison: the boys heard them too. rumors the detective knew the killer was mark. to which the family said-- it's ridiculous. i know there's no way possible he could have done it. my parents were best friends from as long as i could remember. but if that was true, then why would detectives be so suspicious of a man married to his high school sweetheart for almost 33 years? a man without so much as a traffic ticket on his record, let alone a violent act. well, it's true that when wives are murdered, husbands are frequently implicated. and mark did discover the body. but there was another reason. just minutes after mark sat down to talk to those detectives, he volunteered information that sounded to them like a motive for murder. what was going on in our life.

and it scares me when i think about it. keith morrison: it was an odd little story. one day at work toward the end of 2010, said mark, a ups co-worker asked him if he'd ever gone on facebook. no, said mark. he hadn't. well, asked the colleague, haven't you ever wondered what happened to people you used to know? facebook might tell you. and mark thought about it and said, well, there was this girl he used to talk to back in high school. wasn't a real girlfriend or anything, but he was curious about whatever happened to her. so sure enough, the colleague found the woman on facebook. and pretty soon she and mark were texting and talking on the phone, catching up. we always talked when you visited. we kind of got carried away with a little texting here and there. keith morrison: carried away? well, that may be a little strong in this age of sexting and lurid electronic dalliances. they did talk and text.

yes, for several months. even said i love you a time or two. but was it some kind of affair? well, judge for yourself. was there ever any pictures sent or anything like that or was it always just-- there's pictures of just maybe me or her. you know, just little innocent-- you know, we're not into any of that nasty porn. no, no, no. it was just what do you look like now. you know, she sent a picture of her and she goes your turn. she does a quilt. she took a picture of her quilt. showed it to me. just innocent stuff. she had a picture of her and her grandkids. and stuff like that. keith morrison: and not once did they try to see each other. in fact, when an opportunity came up, they decided no. it wouldn't be fair to their respective spouses

of more than three decades or their kids or grandkids. so they didn't. but as mark told the detectives, karen found out what he'd been doing when she went through a phone bill and it hurt her feelings. so he promised to stop. except he didn't. mark went and bought a secret phone to continue that communication. that karen wasn't aware of. keith morrison: it was the woman who put a stop to it. and she sent karen this letter postmarked just a little less than three months before the murder asking for forgiveness. promising it would never happen again. karen told a couple of her kids about it all. she was pretty upset for a while. how important was that? i would definitely say everything together showed that karen was not happy in their relationship. keith morrison: mark told them otherwise that it was a happy marriage. that texting thing just a blip. but the detectives didn't believe it. so they confronted mark. when did you find out that karen was going to leave you mark? leave me? she was never going to leave me.

never going to leave you? honestly. keith morrison: in fact, investigators believed it all backed up what they suspected from that very first night. here, just hours after the murder, when they first accused mark of killing her. i didn't do it. and i mean, it's crazy. and it's just like oj. we need to be out there finding the real killers. right? lapd, they didn't have to go find the real killers. i know you're doing your job. but i would never lay a hand on my wife. i did not hurt her. i did not kill her. i walked in and found her in her condition. keith morrison: mark's family, by the way, said he told them all about that texting relationship they said didn't seem like such a big deal. it sounds to me that it was just them confiding in each other about their marriages and their families. and just an outlet. keith morrison: for youngest son casey, it explained why there had been some tension between his parents a few months before the murder.

there was a good span where they didn't get along. but it was a while before. yeah. and they seemed to be back together again. they seemed better than ever. keith morrison: and those claims by investigators about a pending divorce? not a chance, said the boys. they never were going to give up. they taught us that. i'm sure a little bit of trust was lost. if someone keeps something from you. but it was something they worked on. and they got over. keith morrison: all that grief infected summer, a cloud darkened over the duenas family when casey graduated from high school in june. i remember walking to where we'd be seated and just seeing it's my dad along with other family members. but you know, of course there was-- there was one spot missing. keith morrison: and five months went by that way. as if those early police suspicions had faded away. but of course, we know better, don't we?

narrator: coming up. mark duenas is in for a bitter shock. he was upset. like are you kidding me. narrator: and what his family did next would surprise everyone. this sort of thing hardly ever happens. yeah. like never. craig melvin: when dateline continues. ahh. it's a good day to cough. oh no. bye, bye cough. later chest congestion. hello 12 hours of relief. 12 hours!! not coughing at the movies!? hashtag still not coughing?! ahh! mucinex dm 12 hour doesn't just quiet coughs, it treats coughs caused by excess mucus at the source and controls them for 12 hours. it's comeback season. stubborn chest congestion? try mucinex 12 hour. (man) mm, hey, honey. stubborn chest congestion? looks like my to-do list grew.

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trump. mr. trump is expected to begin his second term by signing more than 50 executive orders. the inaugural events will be inside due to poor weather in washington, and the first wave of israeli hostages were released from gaza sunday after the cease fire between israel and hamas took effect, nearly 100 palestinian prisoners were 100 palestinian prisoners were also released by welcome back to dateline.

i'm craig melvin. karen duenas was brutally murdered, leaving her loved ones devastated. adding to their grief were investigators' suspicions that karen's husband mark was involved. mark told detectives he'd a secret phone relationship with a former high school crush and that karen was upset when she found out. now another surprise was about to jolt the duenas family. here again is keith morrison with a killing in cottonwood. keith morrison: it was evening in cottonwood, california. october 5, 2012. five months to the day after the murder of karen duenas. her widower mark and their son casey were watching tv. there was a knock at the door. and when mark saw the detectives-- he was upset. couldn't believe it. like are you kidding me. keith morrison: they were not.

detectives that suspected mark all along, and now they had a warrant for his arrest. mark duenas was charged with first degree murder, held on a million dollars bail to await trial. to see him in that situation. it's surreal. and you hope the system works because there's an innocent man up there having to go through this. keith morrison: the whole extended clan, including karen's family, told anybody who would listen that the police made a huge mistake. i've never heard him call anybody a name. i've never-- he just isn't that type of guy. i can't think of one time where he raised his voice to anybody. craig melvin: that family support was what persuaded an attorney 600 miles away in southern california to take the case. ron powell is his name. at first i'm not thinking i want to go up there. but you know, when i saw her family saying, well, can you help us, that type of stuff. and us meant mark. that's when i started to think, you know. the victim's family wants the accused

represented by you because they believe he's innocent? correct. that's sort of a once in a while thing. hardly ever happens. yeah. like never. keith morrison: but 14 months after the murder, when went on trial, the family, his, karen's, and theirs, filled the galleries every day to support him. you were there because you know that person. the judge allowed cameras in court, but no audio. so we can't play you the testimony of that woman from idaho and decided to conceal her identity. that's the one he texted and phoned but hadn't seen in more than three decades. still, was to be with her, said the state, that mark killed his wife. and on the stand. at one point, she said mark had mentioned that if they were meant to be together, something bad would have to happen. keith morrison: the woman didn't seem to know what mark meant by that, but the prosecution claimed he meant he'd have to kill karen. not just so he could be with the idaho woman, but so that he wouldn't have to share his pension with karen,

his wife of 33 years. anyway, said the state, karen must have been angry at mark. and might have told him that night she intended to leave him. she wanted a divorce. the facts of the case showed that something happened that night between mark and karen, whether that be her discussing divorce or whatever the case may be. and he became upset and murdered here. karen. keith morrison: the prosecution based that theory around a story told by some teenagers two or three blocks away who said they heard a scream between 10 and 11 pm. the pathologist testified karen could have been killed as early as 10:30 or as late as 2:30 am. but the state said it must have been 10:30, after which mark must have washed his clothes, slashed the screen to make it look like an intruder came in, then went to bed and waited for son casey to come home from the movie. one of the theories that we did have was that he wanted casey to to find karen.

and he's sleeping peacefully. is that the idea? correct. having covered his tracks. correct. keith morrison: except of course, casey didn't discover the body. so said the state, about 1:00 am, mark had to make the 911 call himself. and when detectives went back and listened to that call, they heard what sounded to them like an incriminating mistake. dispatch: 911 your emergency. mark duenas: i got a-- i killed my wife. [bleep] and blood everywhere. keith morrison: what did he say? i killed my wife, the state claims. then a sound they say is a well-known barnyard expletive. an unintended confession caught on tape. or so said the prosecution. so he got it all together and all planned. and then he blew it on the 911 call. i believe so. i'm sure if you just killed your wife, you'd be pretty stressed on the inside. which would make some things come out that you didn't-- you didn't mean to have come out. keith morrison: but to the defense,

it was quite simply bunk. i've listened to it, i don't know, 100 times now. i don't-- i don't hear that. keith morrison: defense attorney ron powell told the jury mark found his wife just after someone attacked her and told 911 this. dispatch: 911 your emergency. i gotta-- i found my wife. [bleep] and blood everywhere. keith morrison: i found my wife. and then that sound the state claims was an expletive, the defense said was really the word sick. so i found my wife sick. do you think if they heard it that clear that this guy says i killed my wife, and he's the only one home, you don't think they're arresting this guy? if that had happened? what are they waiting for? they didn't arrest him until four months later. keith morrison: and meanwhile, said the defense, police failed to follow up on plenty of evidence. that in a town plagued by drug related crime, intruders intent on theft could certainly have been surprised by karen, then killed her, then fled. there was an unidentified car parked

nearby time of the murder. another car seen speeding away from the neighborhood as the cop raced to the duenas house. the two strangers seen in the neighborhood. and a trail of footprints leading away from the duenas backyard. and as for those screams heard by teenagers a couple of blocks away? the entire block where mark lives hears nothing. the woman next door sleeps with her window open, here's nothing. the person on the other side of the house is jason duenas, who has his window open, and he hears nothing. keith morrison: the defense put on a witness who said karen told her the very week of the murder that she and mark were making plans for a bright future together. and the idea that would kill karen so he could pursue a happily married woman from idaho he hadn't seen in more than 30 years was simply ridiculous, said the defense. it sounds like a great motive when you look at it from a distance. but then when you get to it, it sounds like puppy love. keith morrison: the defense rested

its case in a matter of hours. when it went to the jury, how do you feel about it? i was pretty confident. you could see in the jury's face that they weren't buying this. keith morrison: then something odd happened. the day the jury went out, a female juror overslept. and rather than delay the case, the judge replaced her with an alternate. and yes. on such tiny wheels, fates turn. craig melvin: coming up. jurors get the case and are not impressed. i thought the sheriff's department did a terrible job. really, terrible job? terrible job. craig melvin: when dateline continues. ♪♪ vicks vapostick provides soothing non-medicated vicks vapors. easy to apply for the whole family. vicks vapostick. and try new vaposhower max for steamy vicks vapors.

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at 6:00 only on msnbc. >> msnbc premium gives you early access and ad free listening to rachel maddow. >> chart topping series msnbc original podcast's exclusive bonus content, and all of your bonus content, and all of your favorite msnbc shows now ad keith morrison: the jury in the duenas murder case was a little unusual. not just because of that last-minute switch of jurors, but because several of them had spent careers dealing with the justice system. and they certainly knew what was at stake. this is something that we all had to take very serious. keith morrison: here are three members of the jury. this one is a retired chief probation officer and former cop. he was surprised by the case he said, and not in a good way. i thought the sheriff's department did a terrible job. really? terrible job? terrible job in their investigation. keith morrison: in fact, the jurors we spoke to

said that feeling was pervasive in the jury room. and the 911 call that prosecutors claimed was a confession? the jury couldn't decide what he said. we listened to it many, many, many times. 20 times at least. still couldn't tell really? no. keith morrison: the jury took vote after vote. 10 to 2 for acquittal at one point. but one juror in particular was adamant about his guilty vote. which one? the alternate who replaced the woman who'd overslept. that juror said he's guilty and he's going to have to prove that he's not guilty. and i'm not going to change my mind. i'm going to hang this jury. keith morrison: the judge declared a mistrial. what was that like? it was heartbreaking. we thought my dad would be home that day. keith morrison: afterwards, mark and karen's extended family publicly pleaded do not retry mark. let it go.

you see these people? this is love. this is belief in this human being. this is not question in our hearts. please listen to us and know we love this man. keith morrison: so was it over? oh no, not even close. instead, shasta county's da assigned a new prosecutor to the case. stephanie bridgett. something to know about ms. bridgett. up to this moment, she had never lost a case. not one. her secret? preparation, she said. she is very thorough. by the time you finish reading through it in your preparation, what did you think? i didn't have any doubt that mark was the one that killed his wife. keith morrison: one big change at trial number two? the very first words out of the prosecutor's mouth were the state's version of that 911 call. i killed my wife. blood everywhere.

no jury, she declared, could doubt the content of that call. and prosecutors offered yet another possibly damning statement from himself during his first of three tape recorded interviews with detectives. which again, he willingly submitted to without the presence of an attorney. that's the only cut i saw. keith morrison: in his very first interview, claimed the state, mark slipped and made an admission while describing the wound he said he found on karen's chest. like the guy knew what he was doing or something. because the way he cut her. that's the only cut i saw. and there was tons of blood. there was none there coming out when i-- whoever did-- i don't-- keith morrison: what was that again? listen carefully. there was none there coming out when i-- whoever did-- i don't-- keith morrison: when i found her? or when i did it? no way to know what he might have said.

but the state claimed it amounted to another quasi-confession. the second prosecutor also presented evidence the first prosecutor chose not to use. testimony, for example, from a criminalist who examined the clothes mark wore that night and who found karen's blood, though not visible to the naked eye, all over. there was a big area on the front of his shirt that covered all the way down. there was blood on the back of the shirt. there was blood all across the waistband. down the sides. different spots throughout the shorts. even blood on the inside of the boxer shorts. which you don't think he could have gotten there with his-- by touching with his hands or removing, changing, adjusting? absolutely not. not in all those locations. keith morrison: the prosecutor claimed mark must have washed off some but not all the blood after the stabbing. had a shower in his clothes or something. and then she claimed she'd found the murder weapon.

or what could be the murder weapon. a knife found in the wrong slot in the kitchen butcher block. mind you, there was no blood on it. but its handle was bearing a substance identified as either animal fat or some kind of cleaner. what it tells us is that he had something in the home available to him that could have caused that murder. keith morrison: so means, motive, opportunity for premeditated murder. but would a second set of jurors agree? craig melvin: coming up. they would want evidence. but just how much was there? do you any idea that that's what happened? you don't have a clue. craig melvin: when dateline continues. do your dry eyes still feel gritty, rough, or tired?

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keith morrison: november 2013. a chilly autumn wind played around the corners of that big courthouse in the middle of reading. and inside, defense attorney ron powell fretted that he had been shorn of a certain advantage. because now, the prosecution knew his case. and besides, had added these new wrinkles. the blood on mark's clothes and the knife in the kitchen butcher block. remember, this is a retrial now. they felt this time that they needed to show a possibility of a knife.

they never said this was the knife. they're just showing this knife could have done it. keith morrison: in fact, said powell, the new evidence was no more persuasive than the old. no blood but animal fat found on the knife and some sort of soap? how about somebody used a knife to cut a steak and then washed it? could you wipe all the dna off a knife, you put it in the dishwasher. good question. i've learned now after this trial that blood will never leave clothes, but it'll go right off a knife. keith morrison: as for the blood on mark's clothes, of course there was blood, said the defense. he handled her body. and police didn't see the blood at first because his shirt was red and his shorts were black. and then there was the new prosecutor's insistence that karen was very unhappy in her marriage and wanted a divorce. was it true? no. there's nothing to support it. there's no facts to support it. there's no evidence to support it. keith morrison: this was the issue that went right to the heart of the prosecutor's case. and her contention that the state had developed

a clear idea of just what happened the night karen was murdered. i believe that most likely karen confronted him with information that she had about the affair he was having with the lady in idaho. she probably said that was it. she wasn't going to have it. she was going to get a divorce. that's when he decided i'm going to get the knife. i'm going to go in there-- do you have any idea beyond your own fevered imagination that that's what happened? you don't have a clue. well, you know, all the evidence points to that. so yes, i think that i do. how does all the evidence point to that? we have a person who has been in a relationship with a lady in another state. let me stop you for a minute. you say-- first of all, you said affair. now you're saying being in a relationship. he was doing what millions upon millions of americans have been doing since facebook came along. they hadn't seen each other for 30 years. you can't really call that an affair. here's the big difference. it becomes an affair and crosses the line when you don't

tell your spouse about it. you believe that he was obsessed with this woman? i believe that he wanted a lot more out of that relationship than she did. was it pure fiction? or what was it? well what else could it be? i mean, i know she's got a law degree. i never saw a psychology degree. for mark and karen's sons, the prosecutor's psychoanalysis of their mother amounted to an insult. the da said things about my mom that were untrue. do they know my mom better than i know my mom? better than any of us? they act like they do. there's no evidence. what do you say to people whose reaction is, well, you know, of course you're going to feel that way. this is his family. they've just lost their mother. they don't want to lose their father too. life is so much harder protecting my dad. we would be moved on. we would know what happened. if we thought that was the truth. but we all know with our hearts that's not what happened.

keith morrison: the jury in the first trial had been hopelessly deadlocked came so close to acquitting mark and sending him home to his family. when this thing went to the jury the second time. what were your thoughts? i was concerned. this time i was hoping for a hung jury. because of the way the trial had gone? yeah. because, you know, the best stuff that we got out in the first trial, we didn't get to get that out this time. they knew what i was going to ask and they diffused it. i was still confident. i didn't think he was going to get convicted. but my thinking was if they hang this again, they won't be able to do it a third time. keith morrison: the second jury was back in less than a day. and their verdict was written on fces in the gallery's first row. i still hear the sounds of the boys right behind mark. they're crying. i still hear that. it was very tough. keith morrison: guilty of first degree murder.

sick. i felt like throwing up to be honest. i was sick. i feel bad for the family members because they're family members, and they're not going to be happy with the verdict. but at the end of the day, it's karen who was killed and karen who that verdict was for. keith morrison: what would you say to them? this big extended family out there that doesn't take it got justice at all. well i would tell them that i'm confident that the right person was convicted. keith morrison: mark duenas was sentenced to 25 years to life in prison. and his family will go on believing what they have always believed. that late at night on may 4, 2012, unknown intruders, probably drug addicts intent on theft, burst in, were surprised by karen, killed her, and then realizing what they had done, ran away without taking a thing. jason no longer lives right next door to the home he grew up in.

in fact, the family reluctantly sold the home, the place it happened. the memories and upkeep too much to bear. i mean, it was always-- oh we live in cottonwood. small town, nothing happens here. and then the worst you can imagine happened. keith morrison: casey and his brother troy no longer play baseball for the local college. the days when they look toward the bleachers where their parents always sat side by side are gone forever. that's all for this edition of dateline. i'm craig melvin. thank you for watching. [music playing] hello, i'm andrea canning, anda murder mystery.e." you've got a wealthy family. it's something for everybody.