was there any way that that struggle could have ended without you and your dad killing jason? >> yeah, there is another way. we could have died. >> was it self-defense or murder? with 12 blows of a baseball bat. the verdict that few saw coming. >> lots of fathers hate their son-in-law. >> a lot of don't end up with a dead son-in-law. >> now they're telling their versions only to "20/20." >> he's going to hit my dad with a bat. that's it. >> a life or death struggle. due to a father's love for his daughter early or hatred of her husband? >> he's got her in a choke hold.

if i don't stop it, i'm going to end up dying. >> both are charged with murdering her husband. >> a marriage at the breaking point. her fears. >> it was suggested that jason may have killed his first wife. >> i knew that. >> what? >> you think, maybe that's going to happen to me. >> her secret recordings on of a husband's temper. >> you are talking about something else! >> and her fight for the children sheep was afraid of losing. >> i begged and begged, please don't take the kids. >> now we're taking you up the stairs to the moment of truth. or is it? >> i do not believe that i committed a crime. i believe that i did the right thing. >> good evening. i'm david muir. elizabeth is off tonight.

right here, the shocking case that saw a former fbi agent declared guilty of murder. tom and his daughter molly both declared guilty in the murder of her husband. sentenced to prison for what they say was self-defense. right now, only "20/20" and linzie janis are telling what led to that night of terror. >> reporter: hi, molly. tonight in a "20/20" exclusive you'll hear for from the only people who really know what happened inside this winston-salem bedroom. or more precisely, the only two still alive to talk about it. >> it's horrible. a man died. but a man also attacked my daughter. and a man tried to protect his daughter. molly martens corbett and her father tom martens sat down with us pretrial to tell us their version of events. what do you hope to get across today? >> the truth. >> reporter: molly and tom make for a rare pair of murder defendants.

she'd never broken the law, while he'd made a career enforcing it. working for the fbi for 30-plus years. and yet here they are enmeshed in an international murder mystery. a why-dunnit, that's made news from the mountains of north carolina. >> the closing arguments happened -- >> reporter: -- to the emerald isle. tonight's tale begins in tennessee, where molly martens grew up. while knoxville feels like home today, it is a place molly once ran from after struggles during college. >> i was planning on being a doctor. but really, for the first time in my life, school was hard. you know, i hadn't ever really had to study before. so that was a challenge. >> reporter: there were other challenges. migraines, bouts with depression and general anxiety about her future. molly kept it all inside. >> i thought maybe i would just go somewhere, you know, and

figure myself out for a while. >> reporter: she signs up with a nanny agency and soon receives an inquiry from a man in desperate need. >> jason corbett, who sent me messages requesting that i contact him regarding his children, it was emotional. he had lost his wife. and they were two babies. >> reporter: at age 24, the one inspiring doctor throws caution to the wind and takes the job offered by the irish widower. >> i arrive in ireland, and it's beautiful. >> reporter: so jason's family say that you guys hit it off very quickly, that you guys actually got together and slept together that first night. >> that's not true. but it was very quick. i was apprehensive and concerned that it was too quick. but i didn't want to call up my parents and say, "i'm uncomfortable with this, and i'm coming home. i've failed again." >> reporter: the unusual relationship toggles between

personal and professional. but in short order, molly finds her place in the world. she is needed. she is wanted. she is accepted as a mother figure. >> it was wonderful. for me, it gave me a sense of responsibility. and it filled a void i had that made me feel like i was worth something. >> reporter: you became a mother overnight. >> yes. >> reporter: were you in love with jason? >> i was. >> reporter: jason corbett has many loves. his beer, his favorite soccer team and most of all he loves his kids, little jack and sarah. after three years together, the modern family buys plane tickets to the united states. one-way tickets. >> he loved the united states. and he thought that the opportunities for the children were significantly better. >> reporter: in 2011, irish eyes are smiling and wedding bells are ringing. tom martens gets to walk his daughter down the aisle. >> on the wedding day i was excited for them. and it was a delightful experience, and a beautiful wedding. >> reporter: the kids were in

the wedding? >> they were, of course. they were flower girl and ring bearer. >> reporter: the happy family soon moves to davidson county in north carolina and a home that's tobacco country's answer to ireland's stone castles. four beds, three baths and 5,500 square feet for the kids to run around in. there's even enough space for the in-laws to stay overnight. >> it really was a dream summer. jason was working really hard, but it was a golf course community and he was excited about golfing on his day off. >> from what i saw they were a loving couple. i didn't see anything that would question the relationship. >> reporter: tony turner says jason was the king of the cul-de-sac. >> he was very cordial and he was loved by everyone over here. >> reporter: loved by everyone? >> a gentle irish giant. he was good. >> reporter: meanwhile the kids,

now 6 and 4, are thriving. jack corbett swings a mean bat on the little league team. young sarah is the social butterfly, always impeccably dressed. >> they made friends immediately. it was like a wonderland. >> reporter: molly's got it all, except one thing. jason is refusing to make her the children's legal mother. >> at that time, i felt like he was actually going to follow through with the adoption papers and that, you know, i would feel more confident about securing my rights to the children. >> reporter: it never happened. instead, molly says jason was growing addicted to the narcotic of domination. >> he was very controlling, and he was very possessive. the first few months, you just brush it off. oh, well, he loves me so much, but those kind of things got worse. >> reporter: he was uncomfortable with you socializing? >> he was paranoid that i would develop some feelings for someone else and, or that

somebody would look at me the wrong way. >> reporter: he was worried you were going to leave him for another man. >> he was worried about a lot of things. he'd come home from buying new golf club for $500 and he'd open the fridge, and there would be a case of raspberries. and that would be it. "we can't afford raspberries." and he would throw the raspberries on the floor. >> reporter: according to molly, it is a side of jason no one sees because to friends, he's the life of the party. the husky 260-pound irishman always has a smile on his face at neighborhood gatherings. but in private -- >> he would dictate what she should wear, or what she should shop for, or when she should be home, or when she should or shouldn't leave, or text her repeatedly, or engage in just various forms of, you know, controlling behavior. he would demand to see her phone, look at her computer history, that sort of thing. >> reporter: molly says the

fights were escalating. and says the kids witnessed them. this is son jack's recollection when he was later evaluated by a social worker. >> when he would get mad what would he do? >> physically and verbally hurt my mom. >> did you see him? physically hurt her? >> a bunch of times. >> what did you see? >> punching, hitting, pushing. >> reporter: did the physical abuse become more frequent or more extreme? >> everything became more frequent and more extreme, except for the apologies. they became less frequent and less extreme. >> reporter: if you're thinking molly should pack a bag and run, she says she considered it. she visited a lawyer who told her to document any abuse, which she did. making surreptitious audio recordings. >> i'm talking to you. is this how you treat -- is this, you just ignore me? i said i'd like to have dinner

with -- i'm talking to you. i shouldn't have to say it over and over. i shouldn't have to say molly. >> can you guys get out the stuff for pancakes? >> see? there you go again. i'm talking to you and you're still going on talking about something else. >> stop fighting. >> reporter: molly is caught between a rock and a hard place. without a legal adoption, she has no shot of custody in the event of a divorce. she says the stakes are too high to simply walk away. so you suffered because you didn't want to lose the children. >> i never would have left the children. you know. i couldn't imagine. sometimes i thought, "maybe i'm being selfish. maybe their life would be better, you know, if they don't have to deal with this." but ultimately, i always came to the same conclusion that, you know, it wouldn't be better for them to lose a second mother. >> reporter: tom martens knows his daughter is suffering, but decides she doesn't need another man bossing her around. >> i wasn't going to interfere in molly's marriage. that was molly's marriage.

>> reporter: a marriage she says that only gets worse when the lights go out. >> sometimes he would be angry and choking me would turn into something sexual. or sometimes the other way around. >> reporter: so sometimes he would choke you in anger, and sometimes he would choke you during sex. did that scare you? >> everything always felt so real and so scary in the moment, when it was happening. >> reporter: did you ever pass out? >> i did. it did always make me think of mags, his first wife, and wonder if that's what happened to her. >> reporter: mags fitzpatrick, who suffered from asthma, died in the middle of the night. the official cause -- a heart attack. but tom martens remembers a startling conversation he says he once had with the dead woman's father. >> his name was mikey fitzpatrick. and you know, i thought i was just making polite chit-chat, polite conversation. and i said, you know, "what do you think of old jason?"

and his response was, "i think he killed my daughter." and i go, "whoa." you know, i'm not really expecting that kind of thing. >> reporter: from ireland, the fitzpatrick family later denied the conversation ever happened. but molly had heard the same allegation. at some point, it was suggested that jason may have killed his first wife, that perhaps it wasn't an accident. >> yes. it definitely was. and prior to that, i mean, i knew that. >> reporter: what? >> you know, the first time and second time and the third time and the 20th time that you are suffocated or strangled or someone holds their hand over your mouth or a pillow over your face, and you can't breathe for an extended period of time, you know, you think, "oh, well, you know, his first wife died at 3:00 in the morning, and maybe that's going to happen to me."

>> reporter: coming up -- something very bad is about to happen. >> he's already gone this far. and he's going to kill us. >> reporter: details of a deadly night, when we return. ♪ tired of wrestling with seemingly impossible cleaning tasks? using wipes in the kitchen, and sprays in the bathroom can be ineffective. try mr. clean magic eraser. simply add water, and use in your kitchen for burnt on food, in your bathroom to remove soap scum, and on walls to remove scuffs and marks. it erases 4x more permanent marker per swipe. for an effective, multi-surface clean, use mr. clean magic eraser. brand power. helping you buy better. jimmy's gotten used to his whole yup, he's gone noseblind. odors. he thinks it smells fine, but his mom smells this... luckily for all your hard-to-wash fabrics... ...there's febreze fabric refresher. febreze doesn't just mask, it eliminates odors you've...

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>> my name is tom marten. >> reporter: in the early hours of august 2nd, 2013, tom marten makes a stunning call. his son-in-law is dead on the floor. bludgeoned with a baseball bat. it's a gruesome end to a daya d that began ordinarily. >> it was saturday.

>> reporter: molly's parents were never supposed to be with their daughter that day. they make a fateful decision to drive over and visit for the night. were they welcome in the home? >> i knew they didn't feel comfortable in the home. but they knew it was beneficial. >> the martens arrive bearing a special gift for jack. >> i brought over a baseball bat for jack. he thought it was really cool to get any former baseball gear that was a hand me down. >> reporter: after pizza for dinner, everyone settles in for the night with tom and his wife in a guest room, and molly and jason on the first floor. and the kids upstairs. 3:00 a.m., molly awakens to a sound familiar to any parent. >> sara woke up. she had had a nightmare. she came down. and the kids were not supposed to come in the room and wake up jason.

so they would stand outside of the door and whisper until i heard them. >> reporter: she says she gets 8-year-old sara back to bed before tiptoeing to her room. trying not to wake jason. >> he woke up and was angry and i told him sara had a nightmare and he was just furious because sara had been doing this lately and she wanted to be coddled and she was too old for that and i shouldn't have gotten out of bed. >> reporter: molly says it gave her courage to stand up for herself. >> she is 8. all she wanted was her mom to lay with her a couple minutes. and he forgot my parents were there. >> i don't know what woke me up. what i heard were loud voices and i heard a thumping.

something bad but was going on. so i grabbed that little league baseball bat and i ran upstairs. >> he wanted to shut me up so i covered my mouth and he started choking me. at some point, he stopped and i screamed. the next thing i remember is my dad standing in the doorway. >> reporter: what did you see? >> it's awful. he has his hands around her neck and he quickly moves to move her in front of him, between me so he's got her in a choke hold. >> fear was secondary at that point. i was so ashamed my father would see me like that, allowing myself to be treated like that. >> reporter: did you know your dad had a bat with him? >> i don't know that it registered right away. >> i said let her go. and he said i'm going to kill her. he edged toward the master bathroom. i said if he gets the door between me and him, she's dead

and there's nothing i can do about it. so i reached around and i hit him in the back of the head with the baseball bat. >> reporter: and what happened when you hit him? >> if he could have gotten angrier, he did. >> reporter: tom said it didn't stop jason. he kept dragging molly towards the bathroom. >> he made it to the bathroom. but i'm too close. i'm in the bathroom with him. and i hit him again. i mean, i have room now, and i hit him hard. back of the head again. >> reporter: you hit him hard? >> yeah, i did. he still got her by the throat but he changed his tactics. he decides to come back at me. and i'm swinging the bat. and he catches the bat in his hand and he sends me flying across the room. >> jason just grabbed the bat away. it was like it was nothing. he could choke me with one hand and grab the bat with the other. he was just so much stronger. and i was screaming, don't hurt my dad. don't hurt my dad. and i thought he's going to hit my dad with the bat and kill my father.

>> i get up and i rush him. i grab the bat and hang on for dear life. i'm trying to hit him with the bat or elbow. hit him with my fist or anything else. i'm going to hang on to that bat and he goes down. >> reporter: he went down. >> he went down and i realized, okay, he's not going to get up. looks like the threat is over. >> reporter: this version of events will eventually be challenged. what we know is around 3:00 a.m., tom martens makes this call to 911. >> what's going on? >> he's in bad shape. we need help. >> what do you mean, he's in bad shape? he's hurt? >> he's bleeding all over. i may have killed him. i hit him in the head. >> with what? >> a baseball bat. >> yes, ma'am, he said i'm going to kill her. >> reporter: the 911 dispatcher instructs tom to give cpr to jason. he hands the phone to his daughter. >> i need to you calm down so we can help him. >> i'm certified. i just can't think.

>> you have to stay calm. >> i'm thinking he's going to sit up and start choking me again and it was terrifying. >> reporter: did the kids sleep through that struggle and the 911 call? >> the kids did. i keep their rooms closed and my door closed because arguing was a common theme. >> reporter: and your mom was downstairs the whole time? >> my mom was in the guest bedroom. my dad told my mom to stay in the room with the dogs. >> reporter: ems and police arrive and take molly and her father to separate patrol cars. and bring them in for questioning. >> i was told, don't worry, it looks like self-defense. >> it looks like self-defense. i don't think there's going to be an issue with that. >> reporter: molly and her father are photographed and told they're free to go. deputies drive them back to the house about seven hours after the incident. >> the sheriff was there. i said, how much longer are you guys going to be here?

we're done. >> reporter: they were finished processing the scene that quickly. >> yes, they were done. >> reporter: but investigators are just getting started. and to them, what looked like self-defense soon looks a lot like murder. they are alleging you finished him off. did you murder jason? there's more to the story of what happened that night and it's about to cost molly her reputation, her freedom and even worse, the children who have called her mommy for eight years. >> i begged and begged, please don't take the kids. >> stay with us.

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>> reporter: in the aftermath of jason corbett's death, there is a bitter divide, as wide as the atlantic. two families, in two countries, with two very different notions of the man he was. in the medieval city of limerick, ireland, hundreds of mourners eulogize a loving husband and father. jason's casket is adorned with

the word "daddy." but stateside, his widow molly, adamant that he abused her for years, is desperate to secure custody of 10-year-old jack and 8-year-old sarah. >> you think that they're gonna see the truth and that everyone is gonna recognize that, that you're the mother to these children. >> reporter: this is jack in an interview with a social worker. >> do you like her? >> yes. >> and you said you wanted to stay with her? >> yes. >> reporter: but jason's will, written before his marriage to molly, states that both children are to be placed in the custody of his sister tracey in the event of his death. and tracey flies to north carolina, determined to execute that wish. molly says she is stunned when, after a guardianship hearing, a woman from social services arrives with an order to take the children molly has raised for eight years. >> i begged, i begged, begged for her to -- to think about our lives and think about what she was doing.

"and please, please don't take the kids." they were crying and screaming. "don't take me from my mommy, don't take me from my mommy." and i took them out to the van. and i buckled them in. you know, i told them that i loved them and i'd see 'em soon. they drove off, and i melted. i just melted into the driveway. >> reporter: the next day, molly is granted one hour of visitation with the children. there are tearful hugs. she gives sarah her necklace as a memento. and she struggles to keep her composure. >> they said if i cried or the kids got upset, that i would be removed. so i did a good job of holding it together and -- for them. we looked at pictures. >> that's you, that's baby sarah. remember when we went to see santa? >> reporter: she says she was later sent a letter they wrote.

>> it said that, "i love you very much times 999 billion. we will never leave you. you're the greatest mom we could ever have." and yeah, i never saw them again. they were taken the next day to ireland. >> reporter: she posts messages like these on facebook, including her phone number and e-mail in the hope they can contact her. and she makes a plea on an irish radio show. >> i want someone to tell them that i love them and happy birthday, kiddos, with all of my heart. >> reporter: in return, she receives this voice mail from jack. "hi, mom, this is jack. i miss you and i love you, keep fighting really hard, i love you so much." >> reporter: while molly's focused on her fight for the children what she doesn't know is that police are focused on her and her father. they no longer see her as a suffering widow. now she becomes a suspect. what happened to make this go from justified self-defense to

murder? >> the investigation itself, >> reporter: davidson county prosecutors say they took a hard look at these photos and noticed a vast difference between jason's injuries and the absence of injuries, they say, on molly and her father. how brutally was jason beaten? >> it was horrific. >> reporter: would you have expected to see more injuries on tom and molly, had they been in the kind of struggle that they described? >> they walked away with nary a mark on them. and he left on a board with his skull crushed and his scalp ripped off. >> what can i say? the struggle occurred. i've described it as accurately as i can. and that's what happened. >> reporter: the investigators believe the evidence never lies, and that this bloody brick or paving stone, found in the story.m, tells a convincing the story of a wife in a murderous rage. in her police interview, molly admits she hit her husband with it. >> i hit him on the head. >> you hit on the head with what?

>> with a brick on my nightstand. >> reporter: why would there be a paving stone in your bedroom? >> the kids and i were going to decorate a number of paving stones -- anyway, it was left on my nightstand. >> reporter: but in our interview, her lawyers advise her not to discuss what she did with it. did you take action and hit jason yourself at that point with the paving stone? >> it's just not something that i'm prepared to talk about right now. >> reporter: prosecutors are convinced that brick shattered both jason's skull and molly's self-defense claim. >> and when she was crushing his skull with that brick, she had anger to assuage and resentment to address. she addressed those on his head. >> reporter: what you are saying is that tom and molly beat jason after he was already down. he was no longer a threat. >> yes. the physical evidence suggested that he was still being struck in the head after he went down. >> reporter: eventually

prosecutors conclude the g-man and his daughter have cooked their whole story, and they charge molly and tom with second degree murder and voluntary manslaughter. >> molly marten and her father thomas have surrendered themselves. >> this morning, both are charged with murdering her husband. >> reporter: for jason's family in ireland, who had bombarded the d.a.'s offices with letters, demanding justice for jason, it is welcome news. >> we want to express our appreciation to davidson county and to the investigators for their hard work and determination to uncover the truth. >> reporter: it's a huge story in ireland. and the irish tabloids immediately have a field day, dubbing jason a gentle giant, and molly as the "merry widow." painting her as a gold digger with mental problems. but tom martens, ironically an expert himself in processing crime scenes from his days at the fbi, says the investigation was flawed. he says he was stunned that

after their police interviews, he and molly had no further contact with the sheriff's office. >> what i thought would happen next was that they would want follow-up interviews. pretty logical, you know? >> we were ready for them to call us any time to be questioned again about any memories that may have resurfaced when you're not in a state of shock. >> it's not worthy of a second interview and i'm being charged with second degree murder? >> reporter: how do you feel going into trial? confident? >> i feel worried, but righteous. >> reporter: are you guilty of murder? >> no. >> reporter: is your father guilty of murder? >> no, he's guilty of saving my life. >> reporter: stay with us. okay, i never thought i'd say this, but i found bladder leak underwear that's actually pretty.

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new developments in the father/daughter murder trial so many are following. >> reporter: tom martens and his daughter molly walked in a north carolina courtroom facing charges of seconds degree murder. tom martens took the stand and told jurors he did what any father would do. you were defending your daughter. >> i'm going do what i had to do

to save her life. >> reporter: did you think he was going to kill you? >> yes. once it starts, it is what it is. it's a fight. you either fight and lose or you fight and win. >> reporter: but prosecutor allen martin started chopping at the story like the trunk of a carolina pine. >> there was so much that didn't make sense. the physical activity that he had described between he and jason would flip from being being overpowered to seconds later, powerfully overpowering that same man. >> reporter: prosecutor greg brown honed in that his wife was absent from the account. where was she in the violent struggle? >> i asked him a number of questions about where she was when the noise was taking place. when he indicated he was thrown to the floor and no wife came running up the stairs to check

on him. no wife called 911. it was incredulous. >> reporter: put yourself in his shoes. he's a father. he walks in, sees his daughter being stro being strangled by his son-in-law. you tell me you wouldn't try to intervene? >> i'm telling you i don't believe that's what happened. >> reporter: prosecutors want to focus on the physical evidence like the brick and the blood spatter in the bedroom. what does the blood spatter tell us? >> tom marten said when jason went down, the threat was over. and in this particular case, the blood spatter information that was testified to showed that jason was down and still being bludgeoned. >> reporter: they point to pictures like these, noting that most of the blood spatter is on the lower half of the wall with the area above relatively clean. prosecutors say that

demonstrates jason was still being hit after he was down. did that happen? >> no, that didn't happen. the last hit, he was still standing up and hopefully, you know, i'd like to think there is science to prove that. because the truth is the truth. >> reporter: the prosecution believes that the truth is, molly and her father killed him with malice. they turn to the past. you had one witness who used to work with tom martens and he said he didn't like his son-in-law. >> he actually said, that son-in-law, i hate him. >> reporter: but lots of fathers hate their sons-in-law. how do you get murder from that. >> well, a lot of the fathers don't end up with a dead son-in-law and a baseball bat in hand. >> reporter: did you murder your son-in-law? >> no, i didn't murder my son-in-law. and i would challenge any reasonable man, much less a reasonable father to say that this was a necessary force. i used the force that was

necessary to end the threat. >> reporter: but at trial, prosecutors challenge the notion that there ever was a threat that night. going on so far as to float a possible motive for murder. that jason may have been considering returning to ireland and taking the two most precioius people in molly's life with him. >> molly's life was about those children and she wanted the kids. >> reporter: she wanted to kill for it? >> apparently so. >> reporter: and the defense attorney saying molly's story of being attacked could have been corroborated if investigators had done a better job. >> everything that pointed to molly being the victim of strangulation, which she was, they ignored. they didn't check jason's hand and there it is. >> reporter: this crime scene photo shows a blond hair that investigators never tested. they say molly was a victim of

abuse that night, and for years before it. >> the family took the children to ireland. they could have brought him back and let them testify. that was not going to happen in a million years and the judge knew that. >> reporter: that might not have helped molly. before the trial, they spoke to jack and this time, he denied jason had ever abused her. was there anyone else that could testify? >> the only way was to force molly to testify. molly has a constitutional right not to take the stand. >> reporter: why not put molly on the stand? >> why? what burden of proof do we have? it's not up to us to prove innocence. >> reporter: and something else jurors never heard. the audio recordings molly says demonstrate jason's abuse. in their closing argument, prosecutors made it clear this case was about more than proof

behind a reasonable doubt. it was personal. >> i am passionate about the case. i very much believe those two people killed a man. made orphans of two children who did not have to lose their father. that argument was for jack and for sarah. >> reporter: coming up, the verdict that shook the courtroom. and the jurors are speaking out. >> there was no doubt in my mind. >> reporter: stay with us. ring a bell? then you have to try always discreet. i didn't think protection this thin could work. but the super absorbent core turns liquid to gel. for incredible protection... ...that's surprisingly thin. so it's out of sight... ...and out of mind. always discreet. for bladder leaks. also in liners.

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>> reporter: after less than four hours of deliberation the jury in the martens case returns a resounding verdict, guilty of second degree murder. the judge sentences both father and daughter to 20 to 25 years in prison. they are led from the courthouse in shackles. >> and this morning a father and daughter in north carolina are headed to prison. >> what an emotional day this has been. >> reporter: the shock wave from the guilty verdict is still reverberating on two continents. >> the wife and father-in-law of limerick man jason corbett have been found guilty of second-degree murder. >> the verdict today was a relief. >> reporter: jason's family feels his reputation has been redeemed. >> this was a good man. jason was a loving man and he was a great father. my niece and nephew were made orphans in a brutal merciless

killing. >> reporter: the prosecution is satisfied. >> and there was justice for jason today. >> reporter: while the defense is not only beaten, but bewildered. this was the worst possible outcome for your clients. what happened? >> i mean, the jury ruled against us. i've been involved with many cases where, in the criminal justice system where the initial ruling didn't go my client's way and that's why we continue to go on and fight. >> we think they got it wrong and we think they missed quite a bit. >> reporter: just how did the jurors decide to convict? three of them kindly sat down with us to explain. >> based off the evidence that was presented there was no doubt in my mind that i made the right choice. >> reporter: that evidence, specifically the blood spatter testimony, and the crime scene photos, sold them on the prosecution's overkill theory. >> once you hit a certain point and you do not stop -- it's no longer self-defense. >> those images of

jason corbett's skull were so graphic. nancy, you actually threw up. >> yes, ma'am. >> i don't think there's anything or any experience in life that could prepare you to look at those pictures. >> reporter: but the lack of injuries on molly and tom led them even further, into a theory the prosecution never even presented. >> i believe molly made the first blow. >> reporter: why? >> i believe jason was in bed sleeping and she struck him with the paver. >> reporter: and her dad helped her cover it up? >> i think at some point dad came to help out and help cover up. there was blood on the pillow and on the comforter. that may have been the first blow. and then it progressed from that point where he got out of bed, and tried to protect himself, i believe that's when tom had to intervene because of the size difference of molly and jason. >> to me, the choking did not occur.

>> reporter: as for motive, they say perhaps money, perhaps the kids, perhaps just years of pent-up rage. but in any case, after the deed was done, they believe molly and tom took some time to conspire before they called 911. and what was happening during that passage of time? >> setting up the scenario. what do we tell so that we are on the same page and get our stories straight. tom's saying, "maybe because i'm fbi they'll help look the other way to a degree." >> i believe not once in his mind did he think old davidson county, podunk town, would even question his 40 years of fbi experience. i feel like he thought he could outwit davidson county and davidson county outwit the martens. >> reporter: molly tells us that jason is a habitual abuser. emotional and physical abuse she says she has suffered for years.

>> where is the evidence? the defense did not once suggest any of that. >> that's not our fault. that's the lawyer's fault. >> your defense should have defended you. we had to go by what we heard. >> reporter: the jury has rendered judgment, but what about the corbett kids? what do they think of mo you give us comfort. and we give you bare feet, backsweat, and gordo's... everything. i love you, but sometimes you stink. soft surfaces trap odors. febreze fabric refresher cleans them away for good.

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reporter: before the judge sentenced molly and tom martens, the prosecution read an impact statement from young jack corbett, which said, in part, "molly martens is so many bad things. one thing she is not is part of my family. molly martens will not be forgotten. she will be remembered as a murderer." do you believe he wrote every word of that letter? >> this was a handwritten letter. complete with scratch-outs and misspellings from a 12-year-old. i believe from the bottom of my heart he wrote every word after careful thought. >> reporter: when we interviewed molly in may she was a free woman able to enjoy simple pleasures like a jog through the woods. tonight she is behind bars, but she told us it makes little difference. as far as she's concerned her life is already over. do you have any dreams? do you want to rebuild your life one day? >> you can't ever get your life back when something like that

happens. my life ended that day that they took the kids. >> reporter: and if anyone can relate to the pains of parenting, it's her own father. >> we all try to do the right thing, and i tried to do the right thing, and i'd rather live with what i did than live with what i didn't. better to die in jail than have my daughter die before my eyes. >> the defense team has filed a motion to have the guilty verdict appealed. which version do you believe? let us know on twitter. that's our program tonight. from all of us at abc news, thanks for watching. good night. tired of the heat?

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