she really shined as a mother. everything was about her kids. >> i can't even describe to you the feeling that came over me. at that point. we were completely dumbfounded. i don't know how anyone could ever, could ever do that! tonight -- ishs a head-turning new twist in a case that stumped everyone from the start. >> it's the stuff of soap opera. >> a mom of two murdered at work! >> the blood is right by her office door. >> a lotta blood, and a lotta trauma. >> she'd gone in extra early that morning, just a handful of co-workers in that building. was one of them her killer? >> i've referred to this case as almost being like a game of clue. you have a very small group. we know it happens within this building. >> what secrets were inside that

warehouse? >> there were pry marks on her office door. >> somebody moved her body. >> where was her husband that morning? >> the detective asked me if there was any trouble in their marriage. >> whodunit? a stunning new development. >> he's on the property and we don't know who he is. >> but it comes after the verdict! >> i don't get a chance to explain it? >> you're not controlling this anymore. >> nobody really expected anything like this. >> we were as shocked as everyone else! >> i'm lester holt and this is "dateline." here's josh mankiewicz with "after the early shift." >> reporter: they call it the early shift for a reason. it was still an hour before dawn in this small town in northern kentucky, and in a few hours a local warehouse would become an anthill of activity, as the first employees of the morning arrived.

but who among them could predict that before the first coffee break that day, one of their co-workers would be dead? >> i just walked in our office, and i think somebody has killed somebody upstairs in our office. >> okay. what makes you think somebody killed somebody? >> she's laying there on the ground and there's blood all over. >> reporter: impossible to believe in this tight-knit workplace, where everyone knows everyone, but there was michelle mockbee 42, wife and mother, face down in a pool of blood. the sheriff's department would launch an investigation. >> you know that your suspect is one of those people in the building. >> that's right. >> reporter: probing for clues in the victim's own private life -- >> the detective asked me if there was any trouble in their marriage. >> reporter: eliminating suspect after suspect, until there was one. >> he was never on our radar until we saw his truck leaving. >> reporter: and just when it

seemed to be over, it wasn't. >> did you have a sexual relationship with her. are you denying that? >> i don't think it's any of your business. >> reporter: a shocking scandal scrambled everything. >> you're not controlling this anymore. you're not the commonwealth attorney right here -- >> reporter: if you give michelle mockbee's siblings a chance to tell you about their sister, they can't say enough good things about her. >> i don't think there's enough tape to talk about michelle. [ laughter ] >> she was our big sister, our role model. >> michelle was um, just the most amazing sister that you could ever ask for, very loving, caring, giving person. she would do anything for anyone. >> she always had a big smile, and her laughter was contagious. >> reporter: michelle carried her positive spirit into the workplace. she was head of payroll at that warehouse owned by thermo fisher scientific, a worldwide supplier of laboratory

equipment. it was also where she met her husband, dan mockbee. >> what was she like? what drew you to her? >> michelle was funny, attractive, intelligent. >> i've heard you say that pictures kinda don't do her justice. >> no. no, no. michelle was much more -- there was a vibrantness to her. i mean she was beautiful. >> reporter: it was at a thermo fisher christmas party back in 1999 that dan first summoned the courage to ask her out. >> you'd been thinkin' about michelle? >> oh, absolutely. i'd been workin' on her for a year, so. >> reporter: he asked michelle to stick with him that night. and she did. and then everything went sideways. >> it was the worst date in the world. >> what went wrong? >> just -- i don't know. i was totally off my game. i couldn't speak. >> and i thought, "oh gosh, i've done screwed this up totally. this was terrible." but then i asked her out again and she said yes and --

>> well, maybe you did somethin' right. >> i must have. i don't know. or she felt sorry for me, gave me another chance. i don't know. >> reporter: michelle and dan married in 2001 and continued to work together at thermo fisher. not long after, along came two daughters. but even as busy parents, dan and michelle always planned a date night every other monday. memorial day 2012 was no exception. >> how was she that night? happy? >> absolutely. >> normal? >> uh-huh. normal. >> reporter: the next morning, michelle got up to go to thermo fisher even earlier than usual, to wrap things up before enjoying some "staycation" time with the family. dan stayed at home, he'd already started his week off. >> she wakes me up, kisses me goodbye, says, "i love you," and went to work. >> and that was the last you saw of her.

>> that's the last i saw of her. >> reporter: at 5:53 am, a security camera captured michelle's car as it arrived at the parking lot. she stopped by the warehouse's time clock and headed upstairs to her office. about an hour later, a supervisor named ed yuska noticed a big stain on the upstairs hallway carpet. he started looking around the area, with help from a co-worker -- the janitor, david dooley. >> ed was out on the mezzanine just part of the ways and i was holding the door. and there was just -- he said, "there's a dead body layin' there." >> what'd it look like? >> i just saw from the knees down. i didn't see the whole thing. but honestly i'm glad i didn't look because i'd never been around anything like that. it was kind of frightening for me. >> reporter: someone inside thermo fisher had killed michelle mockbee. but who?

and just as puzzling, why? when we come back -- lockdown! the hunt for a killer begins. >> there were pry marks on her office door. >> reporter: in this giant warehouse, a giant question, had someone carried out the perfect crime? >> there is actually industrial strength bleach there rubber gloves everywhere. i mean if you needed to commit a murder, this place has it. joey here is a chihuahua. he's got unique features that make him different than - say - a shih tzu or a yorkie and definitely different than this german shephard. hey, big guy! that's why at petsmart we carry royal canin breed health nutrition formulas. tailored nutrition and uniquely designed kibble for their specific needs. now spend $40 on royal canin and save $10 on your next purchase and when you buy any bag of dog or cat food we give a meal to a pet in need. petsmart - for the love of pets.

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♪ >> reporter: tuesday morning, after memorial day, deputies from the boone county sheriff's department responded to a call of a person down at the thermo fisher warehouse.

they rolled up to the front door and were directed upstairs. the csi team that arrived soon after found hints of what had happened -- a trail of blood in the hallway. a larger bloodstain showing smears when lit up, as though someone had attempted a clean-up. the body itself was found in an unused mezzanine area where someone had also stashed michelle's purse and a bag holding employee timecards. >> obviously we felt like the body had been moved. >> reporter: putting the story together was now the job of lead investigators bruce mcvay and everett stahl. >> tell me a little bit about the building where this takes place. >> thermo fisher scientific is a company that ships medical supplies. kinda like an amazon for medical supplies. it's a large warehouse. >> reporter: how large? try the size of four football fields. that is ulcer-inducing acreage for an investigator searching

for clues. but on the plus side, the warehouse was also a secure facility. detectives say it's pretty hard to get inside if you're not an employee. >> so you know that your suspect is one of those people in the building. >> that's right. >> reporter: that very morning, the sheriff's department put thermo fisher on lockdown. no one allowed in or out. deputies took a headcount -- thirteen workers were on site. detectives began interviewing them, one by one. >> i'm sitting actually closer than you and i are sitting to the people that i'm interviewing. and i can see -- with each person i talk to, there's no blood, there's no evidence that they have been involved in anything. >> so if it's one of these people you're interviewing, they've disguised it well? >> they have. >> reporter: dan mockbee says back at home, he started hearing about an incident at the warehouse. he drove over, and was escorted inside by detective stahl. >> everett stahl sat me down at a table and started to ask me a few questions.

and i looked at him and i said "excuse me, officer. my wife works here. i really need to know that she's all right." and that's when he told me that she was deceased. >> his reaction was pretty excruciating to watch. i still had to press on and i still had to move forward with my looking at him as a possible subject. >> reporter: while dan mockbee was being questioned, michelle's family was starting to get word. her sister jennifer -- >> i think i threw the phone down. and i'm just, like, "no. no. this isn't happening. this isn't real." >> reporter: as investigators wrapped up their first major sweep of thebuilding, they were puzzled -- >> there was really nothing out of place in this facility. after all the searching, the offices, the warehouse, there was just nothing. >> reporter: it didn't help that thermo fisher's shelves seemed

perfectly stocked for a criminal. >> there's actually industrial strength bleach there -- >> that's stronger than any you could buy in a store. >> that's right. rubber gloves everywhere, plastic bags. i mean, if you needed to commit a murder, this place has it. >> reporter: the only sign of anything amiss in the entire warehouse? michelle, as head of payroll, had a locked office -- and it looked as though someone had tried to break into it. >> you could tell that because? >> there were pry marks on her office door. >> what was in that office that anybody would want? >> that's the mystery. you know, we talked about money, but there was very little money if any at all. >> reporter: the following morning, thermo fisher employees came back on the job, shell-shocked about the death of their co-worker and jittery about possibly working alongside her killer. at a command center meeting at the sheriff's office, detectives put their heads together and drew up a list of potential suspects, based on the last people to see michelle mockbee

alive -- or the first to find her dead. ed yuska, the supervisor -- >> he was one of the two that found the body. >> reporter: dave dooley, the janitor -- >> dave dooley was with ed yuska when the body was found. >> reporter: doug tungate, a temp employee, and joe siegert, a warehouse worker. >> doug tungate and joe siegert were the two that saw michelle when she came in. >> reporter: and dan mockbee -- >> of course, dan mockbee, because he's the husband. >> reporter: a short list of potential suspects for prosecutor linda tally smith. >> i've referred to this case as almost being like the game of clue. because you have a very small group. and it's a matter of accounting backwards and excluding people. >> reporter: so that's what faced investigators. in which room? with what weapon? and finally who? coming up -- detectives start with michelle's

husband, dan. where was he the morning of the murder? >> i was sleeping. what a great alibi, right? >> i said, well, why'd you sleep on the couch and she sleep in the bed? it made us want to take a closer look at dan. >> when "dateline" continues. oh, look... another anti-wrinkle cream

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♪ >> reporter: michelle mockbee's siblings remember her as the big sister who literally couldn't lose. >> she was the contest queen. she won every contest there was, for, like, a two-year run. >> yeah. you name it. she won tvs, flat screen tvs. >> tickets to everything, gift cards -- you know, everything -- >> super bowl parties. >> lucky. >> she loved it. it made her so happy. and it made her even more happy to share her winnings with other people. >> reporter: but now it was michelle's family that had lost so much. >> we were completely dumbfounded as to why anyone would want to hurt her. >> reporter: as investigators worked through their list of

five initial suspects, one by one, like the prosecutor's game of clue, they started at the most obvious square one -- the victim's husband. >> dan was a suspect almost from the get-go. were you guys aware of that? >> i was aware of it. because the detective that came to my house asked me if there was any trouble in their marriage. to which i replied, "no. not at all." >> i not for one second thought that dan would be responsible, ever. and i don't think any of us did. never. >> reporter: but detectives weren't so sure they peppered dan with questions. including the big one. >> when police asked you where you were at the time your wife was killed -- >> i was doin' what most sensible people are doin' at 6:00 in the morning if they don't have to get up and go to work. i was sleepin'. what a great alibi, right? i'm home in bed. it's not a very good alibi, but it's the only one i had.

>> reporter: but exactly where he was sleeping that night raised a red flag for detective stahl. dan volunteered he was downstairs on the couch. was that a sign of trouble in the marriage? >> i said, "well, why'd you sleep on the couch and she sleep in the bed?" and he said, "well, you know, typically the girls sleep with her and i get off of my shift late. by the time i get home she's already in bed for the next day." so he had just made a habit to sleep in on the couch. it made us wanna take a closer look at dan. >> reporter: detectives weren't the only ones interested in the husband -- a cadaver dog named little joe had been called in to search outside the warehouse. the dog searched two cars with no success. but then he went up to a third vehicle -- a silver minivan. >> the dog did have some interest in the back of that vehicle. >> reporter: detectives knew that the silver minivan belonged to dan mockbee. >> he was finding nothing. there was no findings of human remains or blood. >> reporter: a disappointing dead end. while dan was feeling the heat,

detectives were pulling numbers off michelle's cell phone and tracking down truckers who had delivered to thermo fisher. and of course, stahl and mcvay were taking a hard look at the other four names on their initial suspect list -- two men who were the last known to see michelle mockbee alive. one, a warehouse worker named joe siegert, had seemed unusually unemotional about michelle's death when he was first questioned. >> he was one of the ones that made it to the top of the list. >> joe presents himself as a loner. kind of a dry, dark sense of humor, and personality. >> reporter: the other guy at the time clock that morning was doug tungate. doug was a temporary employee. a newcomer to thermo fisher -- and an outsider. >> we started looking into his past. saw that he had a couple felonies, and some alcohol issues. so, we thought, "hmm, this might be a good guy to look at."

>> reporter: then there was david dooley, the janitor. he and his wife janet had cleaned at thermo fisher for years. david was one of the two to find michelle's body. >> detective mcvay interviewed him the day of the homicide, and really nothing that put him to the forefront of anyone's mind. >> reporter: and last, there was ed yuska. he was the supervisor who called 911 after finding michelle. >> the blood is right by her office door. it looks like she never got in her office. >> reporter: detective stahl found out that ed yuska had some health issues. >> the thought that ed could do all this to michelle, drag her down the hallway and get her to the mezzanine logically to us says ed's not our guy. because he physically probably couldn't have done that. >> reporter: which made detectives feel comfortable eliminating ed yuska from their suspect list. and so then there were four.

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>> reporter: red ribbons were popping up all over town in honor of michelle mockbee. but all the community support in the world still couldn't answer the family's questions. >> i feel like we're all kind of in limbo, we don't know what to do, how to move on just yet. >> we didn't know what this was all about. we didn't know if it was somebody after our family. why they would be, we don't know. but, we didn't -- know. >> reporter: early on, the investigation had yielded frustratingly few clues on the four remaining lead suspects, but the detectives' commander, major ben huff, kept up hope. >> i knew once we can get that just one little bit of lead on this investigation it would open many many doors.

>> reporter: and meanwhile, stahl and mcvay decided to turn up the heat on the four. starting with the husband, dan. >> we asked him, "would you take a polygraph for us?" >> you agreed to take the polygraph. >> yes, sir. that's a scary thing. >> because if it goes wrong, all of a sudden there's a case against you? >> right. it was nerve-wracking. i mean, it -- i took a deep breath like this and the guy's like, "hold on, hold on. y -- you -- you can't do that. it -- you know, it's registering on the sensors," and you're like, "what if i took a deep breath at the wrong time?" >> reporter: but dan passed the polygraph. and this time, the husband didn't do it. and so then there were three. and around that time, major huff and his team were checking the security footage around the building and spotted something they thought was unusual. >> "there it is." >> reporter: a vehicle in the parking lot, not entering, but leaving around the back of the building. >> bright red, fire engine red, chevy pick-up truck, 2-door. that's not a normal route for

any employee to take. >> reporter: detectives matched the truck to its owner, david dooley, the janitor. >> dave dooley's truck is seen leaving the parking lot at 6:31 that morning. >> right after the murder. >> that's right. that's right. >> reporter: and detectives could tell from the security tape that dooley had returned to the warehouse around 7am in time to be with ed yuska when he discovered michelle's body. detectives went to the apartment david dooley shared with his wife janet to ask him where he went during that half-hour trip. >> they got there at six -- there about 6:30 in the evening. and i kinda figured it would happen just to do a follow-up. >> he told me why he left the building, that he was trying to call his wife. she wouldn't answer the phone. >> my wife does take ambien to help her sleep at night and i went home to check on her, make sure she was okay. >> reporter: his wife, janet, said dave often worried about her health, and would check in on her. >> he drives me crazy with, "janet, did you take your medicine? janet, did you take your vitamins today?" that's just the kind of person

he is. >> reporter: but detectives wondered, did he really come home to check on his wife? or, to get rid of evidence? >> we started working on a search warrant for the residence, and for the truck. >> you execute those search warrants and you find bloody clothing? >> no bloody clothing. >> bloody footprints? >> no. >> stuff taken from the crime scene that shouldn't be at his house? >> no. >> some kinda murder weapon? >> no. nothing that directly tied michelle mockbee to him. >> reporter: so investigators kept working. they asked two other suspects, joe, the warehouse worker, and doug, the temp employee to take polygraphs. both men agreed. both passed, two more names scratched off the list. detectives had also asked david dooley to take a polygraph. >> and he said, "yeah, i'll take one." >> reporter: but when they brought him down to headquarters -- >> we walk him in, and detective mcvay says, "this is our polygraph operator."

and he stops himself at the door, and says, "no, no, no, i didn't agree to this. i did not agree to this." he said, "i'm not doin' this." >> there was no ask me to do it. it was, "sit down and do it." and i said, "well, i wanna do this with an attorney." >> reporter: dooley didn't take a polygraph at a later time, either, but he says that wasn't his fault. >> i did offer to take the polygraph. and they said "it's too late." >> reporter: over the next few months, detectives focused in on dooley. significantly, he was the only one they could ever identify who left the building around the time michelle mockbee was killed. after eliminating other suspects, detectives now believed they'd cracked the case and that game of clue. in september 2012, the boone county sheriff's department arrested david dooley. michelleal sister jennifer. >> just very glad he's behind bars. that's where he needs to be. >> as to why this happened, we have no idea.

>> i didn't know what to say, i didn't know what to do. i was never goin' home. >> you wanna stop a minute? >> it's fine. i knew i was never goin' home, and i was upset. >> reporter: but then, results from dna found at the crime scene came back from the forensic lab. it turned out, david dooley was not a match. and in the local media, his wife, janet, called for him to be freed. >> we've been telling everyone he didn't do this. nobody deserves to be accused of a crime of this magnitude without something to prove that he did it. >> reporter: but even without forensic evidence tying david dooley to the crime, prosecutor linda tally smith remained confident, deciding to move forward with the case. in september 2014, david dooley went on trial for murder. >> reporter: coming up, pros-our

>> our view has always been david bowly wdooley was in her and she came in answers spr sprooized him. what was he after? pros, sometimes desperate people do desperate things when dateline continues. u something? allergic itch in dogs is aing? medical condition that's more common and treatable than you think. that's why there's prescription apoquel: the revolutionary medicine that's giving millions of dogs the relief they deserve. apoquel goes to the source of the itch to provide relief in as little as 4 hours. woof and apoquel is safe without many of the side effects associated with the use of steroids. apoquel is for the control of itch associated with allergic dermatitis and the control of atopic dermatitis in dogs. do not use apoquel in dogs less than 12 months old or those with serious infections. apoquel may increase the chance of developing serious infections and may cause existing parasitic skin infestations or pre-existing cancers to worsen. do not use in breeding, pregnant, or lactating dogs. most common side effects are vomiting and diarrhea. don't wait. ask your veterinarian about apoquel today.

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talk to your doctor and visit humira.com this is humira at work. >> reporter: michelle mockbee's favorite color had always been red. and since her death, her family

has worn red in her honor. >> you're all wearing your red wristbands today. >> yes. they say, "michelle ann mockbee, in our hearts. 1969-2012." >> that was your idea. >> yes. just a little something to remember her by. >> reporter: there was a sea of red each day, as michelle's family and supporters flowed into this northern kentucky courthouse where david dooley faced trial for her murder. >> on may the 29th, 2012, dan mockbee lost the love of his life. and two little girls lost their mom at the hands of a man who couldn't even keep his story straight from one day to the next. >> reporter: prosecutor linda tally smith began by telling the jurors they wouldn't hear about any smoking gun, but they would hear david dooley's own words which, she said, had

made him the "last man standing" in the detectives' process of elimination. >> it was through this process, that the path kept turning back to one person. the defendant david dooley. >> reporter: the prosecutor explained that at thermo fisher, warehouse employees used hand-held scanners like this one on the job and the scanner data could help locate where employees were around the time of the murder. >> we were able to create, pretty much so, a time record of where everybody was and what they were doing at different points during the morning. >> reporter: jurors heard that almost all the employees were working on the warehouse floor, far away from the upstairs office area where michelle was killed. but where was david dooley? because he was the janitor, he didn't use a scanner. which meant, said the prosecutor, he could have been upstairs near michelle's office during that critical time. the jury got to see dooley on security video from that

morning. >> there's the red pick up truck. >> reporter: his red truck was seen leaving the thermo fisher parking lot. >> the defendant actually left the building that day at 6:31 am which was about a half an hour after michelle walked into the building. >> reporter: the prosecutor showed the jury a photo of fresh pry marks on michelle's office door which she said indicated an attempted break-in. >> our belief has always been that david dooley was in the middle of breaking into her office when she came up the steps and surprised him. and ultimately she was assaulted and restrained. >> because she was a witness to a crime in progress. >> absolutely. >> reporter: the medical examiner said michelle was bludgeoned to death with something similar to an industrial packing tape gun. but after such a violent attack, why was no blood evidence ever found on david dooley? and why wasn't any of his dna left at the scene? the prosecutor argued that's because the janitor worked every

day with cleaning supplies and plastic bags. perfect for removing evidence of a crime. >> at the time david dooley attacked michelle in that hallway, what did he have with him? a rolling crime scene clean-up cart with a trash bag in the middle of it. >> it's my personal belief that when he left that building he took with him a bag containing all of the evidence that was missing from the scene. >> reporter: a cover-up so spotless, only a janitor could manage it, said the prosecutor. it was only his story, she said, that was a mess. >> it's very hard for a person to explain how they can't tell the same story twice. and in these circumstances we had four separate statements from him. >> reporter: detective mcvay testified it was what dooley didn't say in his first interview on the day of the murder that made them take a hard look at him. >> at any time did he tell you that he left that building? >> no he did not. >> reporter: mcvay says it was only in dooley's second

interview at his apartment that he first mentioned leaving work and going home. >> and i came back here. >> ok. what time did you come back here? >> 6:30. i couldn't get a hold of wife and i came home to make sure she was okay. >> reporter: but detective stahl says dooley's wife janet told stahl something different. >> i ask her specifically if dave ever came home that morning, and she says, "no." >> reporter: in a later set of his-and-hers interviews, janet said david did come home to change a pair of ripped pants. >> he had to come home and, you know, just grab a pair of pants. >> reporter: it sounds like an alibi. except, david dooley adamantly denied doing that. >> i never said that. >> okay. you didn't rip your pants? >> no. >> okay. >> reporter: while the prosecutor had focused on david dooley's own words and that suspicious drive away from the murder scene, next the defense was about to point out to the jury all the hard evidence investigators didn't

have on david dooley. >> dna evidence, murder weapon, blood evidence, marks on david dooley. >> reporter: and defense attorneys chris roach and tom pugh pointed out that detective mcvay's critical first interview with david dooley was not recorded, so what can anyone really know about what was or wasn't said? >> without actually having his interview, now we're going based on one detective's notes saying that he didn't go home that day. >> reporter: david dooley says he knows what he told them. >> i did tell them i went home. i was always very adamant about that. >> reporter: dooley never testified in front of the jury, but he did talk to "dateline" about the case against him, and his story that differed from his wife's. >> you say you went home to check on your wife. they talk to your wife and she says, "he never came home." then later, in a separate interview, she says, "he came home because he tore his pants and he came home to change his

pants." so what's the truth and why can't you and your wife agree on the same story? >> we do agree that i came home. i have never heard an interview where she said that i did not come home. this was his testimony. >> the detective? >> yes. as far as i'm concerned it is not the truth if can not be factually proved. >> did you go home to change your pants? >> no, i did not. >> why would your wife say that you did? >> i do not know. we've talked about that a couple-a times. and the only thing we can come up with is she didn't hear me properly. >> reporter: janet says she's been diagnosed deaf in one ear. on the day of the murder, she says she only saw a pair of ripped pants in the house, and thought david said that's why he came home. >> so a person that cannot hear, they put things together themselves through their eyes, and i did. >> reporter: in court, the defense sought to set the record straight for the jury. >> dave didn't change his clothes and dave didn't change his story. >> reporter: also significant

for the defense was the unknown dna found on michelle's body or on her belongings in at least five different places. >> we heard testimony that there were many unknown dna profiles. could one of these unknown profiles have been the killer? >> reporter: the defense also disputed that thermo fisher was a secure facility and noted that something had set off the warehouse alarm system just three days before the murder. >> and you think that's significant? >> yeah, yeah it's significant. that means that someone could have gained access to thermo fisher. >> reporter: after both sides had presented their cases, it was time for closing arguments. now each side would have its last opportunity to speak to the jury. the defense went first. >> no one could think of any reason to kill michelle mockbee. so what motive would david dooley have to kill michelle mockbee?

>> but it was only after the defense had wrapped up its closing that the prosecutor gave her answer to that question, laying out her theory of motive for the first time. >> i would suggest to you that the evidence is right in that stack of stuff over there. you have time cards, you have invoices. all kept in michelle's office. >> you think the motive was the time cards? >> yes. i believe that michelle had actually discovered the fact that he had actually been triple-dipping by clocking himself in, clocking his wife in, and getting paid hourly to do a job that they were already being paid a monthly salary to do. >> that feels like a thin motive. >> sometimes, desperate people do desperate things. >> what about the theory that you were double dipping your pay? >> it is not true. >> you were not double dipping your pay or triple dipping or stealing your -- >> no, we were not. >> reporter: but more importantly, did he commit murder? now, it would be up to a jury to decide. coming up -- we the jury --

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>> reporter: october 9th, 2014. after deliberating for some 16 hours over two days, word came from the jury. there was a verdict. >> we the jury find the

defendant, david dooley, guilty -- >> guilty of the nurder -- murder of michelle mockebee. >> reporter: the jury foreperson told "dateline" that in the end, david and janet's own statements, which jurors felt were inconsistent -- helped them reach their verdict. >> did you have anything to do with the death of michelle mockbee? >> no, i did not. i did not kill her. >> reporter: david dooley was sentenced to life in prison. he filed an appeal. >> you know getting convictions reversed on appeal is a long shot. >> but when you're innocent, it does happen. and it will happen. >> reporter: dooley had lost that real-life game of clue but he was right about one thing -- it wasn't over. that's because two years later, someone in the prosecutor's office found some explosive information about a professional relationship that had turned personal and sent it to the kentucky attorney general's office. >> all of the information about

the personal conversations between the prosecutor, linda tally smith, and the lead detective, bruce mcvay, all of their correspondence, all of that comes out. >> reporter: as brian hamrick of nbc's cincinnati affilate reported, these bombshell disclosures that came out in the press revealed a real-life soap opera, complete with sex, lies and videotape. and it wasn't that the two principals had become involved weeks after the trial -- it was what they wrote to each other that now jeopardized dooley's conviction. >> what was it in there that screamed problems for the criminal case? >> i think linda tally smith's own words were the thing that were most destructive to her. >> because she's clearly writing sort of in an unguarded way to somebody that she had been involved with. >> right. and she never meant anyone -- anyone but bruce mcvay to see these. >> reporter: her words, written

in anger after they broke up, prompted the trial judge to order a hearing that would determine whether dooley's conviction should be set aside. so this past march, the prosecutor and the detective, both instrumental in putting dooley behind bars found themselves on the hot seat, being grilled by dooley's appeals attorney, deanna dennison. >> are you telling me you didn't have a -- sexual relationship with her? >> we were friends. >> you're under oath. >> we were friends. >> did you have a sexual relationship with her? are you denying that? >> i don't think it's any of your business. >> i'm asking you to an -- you're under oath. she'll testify. she'll say. >> yes. >> tell me what it is your answer is. >> i just said, yes. >> ok. thanks. simple. >> reporter: then, dennison challenged the prosecutor, someone not accustomed to being on the witness stand. >> now, let's go to the next paragraph. >> i don't get a chance to explain it? >> i didn't ask you to explain it. you're not controlling this

anymore. you're not the commonwealth attorney right here -- >> objection. >> sustained. >> linda tally smith is trying to keep the damage down. and deanna dennison is trying to inflict maximum damage. and to watch the two of them at work, it's like watching a prize fight. >> now, let's talk about this letter -- >> reporter: at the center of all this was an 18-page letter, in which the prosecutor blasts the detective, by then her former lover, as an outright liar -- both personally and professionally. and she ended up reading her own scathing words into the record. >> "now that i know what a complete fucking liar you are, i am going to grapple with fucking am going to grapple with [ bleep ] ethical issues with every case in which you are involved." >> reporter: she said she was upset because mcvay didn't tell her what was on a security video that he'd checked out. >> "not to mention the fact that you allowed me to go through a complete [ bleep ] murder trial

without telling me the truth about that video. and now that i know it, what the [ bleep ] am i going to do now?" >> what the -- "what the [ bleep ] am i supposed to do now?" >> right. >> that one message from linda tally smith to bruce mcvay really tells the story, doesn't it? >> yeah. and that may be the most damning paragraph of the entire trove of information. >> he says, "8:11 p.m., random dude." >> reporter: the video in question shows a man police call the "random dude." >> it's a little hard to tell exactly what he's doing but he's on the property where a woman is murdered brutally 10 hours later, and we don't know who he is. >> reporter: the prosecutor said the defense was given this video. but defense attorneys say they were unable to watch the video and were never told about the random dude. >> that would have been her clothing. >> reporter: one of dooley's criminal attorneys testified the "random dude" would have had reasonable doubt written all over him. >> i mean, our whole defense was he didn't do it, so if we can point to unknown individuals

that were trying to gain access to the building, that would definitely have been used. >> reporter: remember, tally smith said she didn't know about the man on the video during the trial but finally learned about him from mcvay afterwards. but then, she did nothing. >> she didn't go to the judge. she didn't go to the attorney general. >> reporter: and she didn't go to the defense, either. >> she wrote a letter to bruce mcvay, saying, "how could you do this to me?" >> "and i get to live with the worry that someone on the defense side will find it at some point. and that we'll all wind up in trouble over it. and the entire case will be tainted because of it." you wrote that? >> i did write that. >> reporter: in defense of her actions, tally smith testified she subsequently calmed down and never sent that letter. and besides, she said, the video with the "random dude" was much ado about nothing. >> it doesn't constitute any evidence that someone got in that building. >> was he tryin' to hide his identity?

>> does not look like it to me. >> did he have gloves on so that they would leave no dna? >> not that i'm aware of. >> would it have changed anything that -- about the case? >> no. absolutely not. >> reporter: for his part, mcvay testified he didn't tell the prosecutor about the "random dude" because he was confident he knew who that was and, that he wasn't the killer. but in may, the judge ruled for dooley, saying he was entitled to know about the man on the video. the judge then set aside dooley's murder conviction and ordered a new trial. >> dave found out. and then he called me and, of course he was crying. >> reporter: janet dooley says she's never doubted her husband. >> he was relieved that, finally, he's gonna get a second chance to prove his innocence. we still have a murderer out there. and i'm not gonna shut up until dave comes home. >> reporter: she's confident her husband will be found not guilty next time. the prosecution's case, she says, is weaker, in large part, because detective mcvay's credibility is compromised after the prosecutor branded him a

liar. >> they lie. they cheat to win. and that's what they do. >> after everything's that's come out, you think they got the right guy. >> we absolutely think they have the right guy. we have no doubt about that at all. >> so nothing that's happened since the trial, nothing in the appeal has made you think maybe the jury was wrong? >> no. >> reporter: jennifer and cindy, michelle's sisters, believe dooley will be convicted again. that said, they're heartsick they have to go through another trial. >> this wasn't smart lawyering by the dooley side that got this done. this was a mistake or series of mistakes by the prosecution that essentially handed him this new trial. >> it was definitely disappointing. we were frustrated. and it's unfortunate, but we will get through it. >> reporter: because, they say, their family is strong enough. >> we still laugh. we still have great, happy times. but it's -- it's not the same. it'll never be the same without michelle. what's the most frustrating in

all of this is the fact that it becomes all about david dooley. >> he's the victim. >> it's all about him. >> he's the person -- >> yeah, and -- >> who got treated badly by -- >> it's -- >> the system. >> michelle deserves justice. i mean, she deserves all this to be, we all deserve all this to be over with. >> reporter: that's all for this edition of dateline. tune in to dateline's "saturday night mystery" tomorrow night at eight, seven central. and we'll see you again next friday. i'm lester holt. for all of us at nbc news, goodnight. next at 11:00, a party at tesla. live as the first 30 owners of the model three get key skbloos the weekend heats up. i'll show you which areas warm up to the mid-90s. the news in 30 seconds. .

the curtain has been pulled back. tonight, a big party at the tesla factory in fremont as the model 3 made the debut. elon musk at the wheel. the news at 11:00. starts right now. good friday evening thanks for joining us i'm janelle wang. >> and terry mcsweeney. raj and jessica have the night off. >> irchlts it's the car hundreds of thousands have been waiting for. earlier tonight 30 people got their hands on a