watch that talking point because you may hear a lot more of that from mark zuckerberg when he breaks his silence and finally speaks to the united states congress. that does it for me. you can always check out the beat on 6:00 p.m. eastern on msnbc. >> a young mother went for a ride and vanished. found later, strangled, dumped in a drainage ditch. >> we had a homicide. we had no suspects. >> who would want her dead. >> i asked him point blank, what have you done?

it happened in a safe suburban neighborhood, the kind of place where crime is unexpected. even more unexpected the tiny clue buried in a computer that unlocked the mystery. here's keith morrison. >> reporter: nothing about that morning made any sense. >> it all seemed like such a bad nightmare. this doesn't happen in our happy little world. >> reporter: it was a saturday morning in july. the happy little world suburb of raleigh, north carolina, called carey, a place where a young family would aspire to if you were someone like hanna prittchard, for example. >> there's always lots of friend making going on through someone you meet.

lots of cookouts and family functions. >> reporter: like the one in the neighborhood the night before. so hanna would have heard party stories that saturday morning from her friend nancy cooper. would have. because nancy didn't show up. >> i hadn't heard from her maybe by like 10:00, i called her house. brad answered and he said, she went for a run. >> reporter: nancy was an athlete, training for a half marathon. brad cooper was nancy's husband. >> i was like oh, okay. when did she leave. he told me 6:30 or 7:00. she's not back? >> reporter: weird. if nancy had to cancel their meeting, surely she would have called. hanna cooled her heels. >> at 1, the phone rang and i saw on the caller i.d. it was her house. i answered the phone, hey, where have you been. he said no, hanna, it's brad. nancy's still not back.

>> reporter: now brad was worried. >> i really started to panic. >> reporter: especially when she learned nancy had also stood up another of their friends. they called the local hospital. no sign of nancy. they called nancy's twin sister christa up in canada. >> have you talked to nancy today? she wept for a run and she hasn't returned yet and we're very worried about her. can you call us back. >> you know about this kind of stuff? >> you would think. >> reporter: krista calls her older brother jeff, who is a police officer in edmonton, alberta. >> my first reaction, okay, she's somewhere. she just needs some space or time. she'll turn up. >> reporter: when nancy's parents, gary and donna, heard she was missing, they were gripped by something dark and cold. >> gary said to me, donna, this story is not going to have a happy ending. >> reporter: by afternoon the carey police were involved. >> all i was told on the phone it was a missing persons.

>> reporter: when detective george daniels arrived nancy's neighborhood was already filling up with a small army of her panicked friends. nancy's friends rushed to join in the search. her husband brad made a public plea for help. >> anyone that knows anything, i just want them to contact the police with any information they may have. again, thank you to everyone that continues to come out and help out. >> sir, do you have a flyer? >> reporter: volunteers chased up and down the running trails where she loved to train, she combed the surrounding parks and lakes and woods. this woman they had grown to love since she and brad moved down from canada. >> capacity to make her rather always group of friends feel they were best friends. many ways they were. >> when she walked into a room, that's where people wanted to be. >> reporter: she and brad were like a lot of people in carey, raising a family here, having got their start in another place and time. in brad and nancy's case, calgary, canada. that's where they met back in '98. >> i really liked her. >> reporter: as did nancy's younger sister jill.

>> it's someone who is warm, genuinely saw how much he cared for her. >> reporter: brad became a helpful member of the family, even designed the computer systems in the family business. >> our i.t. guy would say i want to meet the guy who did this, the networking system. he was kind of a legend in the i.t. world. >> reporter: he was so good, that cisco systems invited him to move to raleigh and work for the company. >> smart guy? >> smart guy. >> yes. >> if nancy was to go with him to america, for immigration reasons, they had to be married. so in the fall of 2000, they said their vows, an intimate family affair. >> how did she feel about going to north carolina. >> she was a little yap lensive. there was lots of tears at the airport, fear of the unknown, but i think she was excited. >> reporter: a few years later there were two bmws in the driveway, nancy a vast circle of friends and brad a bright future of cisco where he would become

an expert in the marriage of internet technology and telephones. best of all, two little girls, bela born in 2004, katie two years later. >> the best mother i've ever seen. she played and played and played. she was so hands on. >> reporter: and now, they were putting up missing posters. sunday went by, all day monday, monday evening. someone called 191. >> the chief of the carey police department it is my very sad duty to tell you that the search for our nancy is over. >> reporter: it was a man walking his dog who found her. lying face down in water at the edge of a storm drain near a housing construction site several miles from the cooper home. >> our investigation is now a homicide. >> reporter: now they had to say good-bye. it was a measure of the woman that total strangers joined nancy's family and friends, to share in the sorrow. >> i continue to thank the community for their generosity and support. it's overwhelming. i am you one of the luckiest people in the world. i'm a twin. sorry. i have a bond with nancy that no one in the world has. all i have to do to remember her is look in the mirror. she will always be half of me, of nancy. i love you and i always will. >> reporter: now, of course, a homicide investigation was under way. but for detective george daniels, only this to go on. she had been strangled. she was found wearing only a sports bra and her diamond stud earrings. there were no marks on her body to indicate a beating, no struggle, no sign of sexual assault or robbery. it was a puzzle that landed in his lap. >> she wasn't raped. she wasn't assaulted in any kind of way. the earrings weren't taken. what was the reason for her to be over here?

and then what was the reason for them to do this if nothing was done to her? >> reporter: police soon discover possible reasons and a reality much grimmer than the smiling facade. >> i continue to thank the community for their generosity and support. it's overwhelming. i am you one of the luckiest people in the world. i'm a twin. sorry. i have a bond with nancy that no one in the world has. all i have to do to remember her is look in the mirror. she will always be half of me, of nancy. i love you and i always will. >> reporter: now, of course, a homicide investigation was under way. but for detective george daniels, only this to go on. she had been strangled. she was found wearing only a sports bra and her diamond stud earrings. there were no marks on her body to indicate a beating, no struggle, no sign of sexual assault or robbery.

it was a puzzle that landed in his lap. >> she wasn't raped. she wasn't assaulted in any kind of way. the earrings weren't taken. what was the reason for her to be over here? and then what was the reason for them to do this if nothing was done to her? whoooo.

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from people who said they saw a woman who looked like nancy running that saturday morning. one man said he watched her for a good 30 seconds, then saw a van make a u-turn to follow her. there were other reports of mysterious vans. friday one sped away from a cul-de-sac with no lights on. could any of this be tied to her killer? >> we're not walking away from anything at this point. everything becomes important. >> reporter: like the conversations with nancy's husband brad during the search. he told detectives he and nancy were up at 4:00 a.m. saturday to calm their crying 2-year-old katie and then 6:00 or so, he made two trips to the grocery store, after which nancy announced she was off to run. >> of course we went to find the video records of him going in and out of the store which we did, in fact, find. >> reporter: one of those talks with brad struck detective daniels as odd. when he asked brad, did you contact nancy's family?

>> he had told us no. but it could be because he's frantic about the situation and wouldn't have time to call them. >> reporter: a little more talking and the detective learned there may have been another reason altogether. nancy and brad were having marital problems. >> he told me the last two months they seemed like they were getting better. when i asked him why they had problems. he told me he had had an affair. >> reporter: so daniels tucked that tidbit away and went on for the search for nancy. but after her body was found, things were different. the cooper house became a crime scene. police in and out, turning the place upside down, and daniels kept his ears open. because among nancy's friends and family, people were certainly talking. >> we're getting all this

information and we're having to separate what's important versus what's just part of a marriage. >> reporter: brad remember told detective daniels he and nancy were getting past the tension that his affair had caused. that wasn't quite the story he was hearing from mansy's family and friends. >> she felt very trapped and she didn't know what she was going to do. >> reporter: the marriage, it turned out, had been rocky from the start. brad seemed more married to his job than nancy. then in the spring of 2007, nancy's close friend healther told her she slept with brad. nancy confronted her husband. >> she just wanted the truth so she could fix it and go on. >> he said it didn't happen? >> for a very long time. >> made her feel bad about thinking that it happened. >> reporter: until months later, new year's eve day when brad finally came clean. yes, he told nancy, it happened. but he said, only once. really it meant nothing. they went to counseling and that's when nancy heard what she said was the real story. >> brad says to the counselor, it's been going on for a long time. changes again from the one-night stand to i think i love the woman. nancy came away from that and said i'm finished. >> reporter: they agreed to split, sell the house. nancy would move back to canada with the girls.

and then suddenly, brad canceled nancy's credit cards. blocked her access to the bank account. put her on a cash allowance. >> i recall a time she was in the car with me and she called him and said, you know, i've got $2 and we don't have any diapers. >> reporter: nancy couldn't get a job. she had no green card. she began painting a friend's house to earn extra money. when she did, brad reduced her allowance. >> she must have been furious at him. >> furious would be an understatement. >> also tried to help nancy and she is very proud, she would feel guilty. i'm not going to take your money. this isn't your job to support me and my kids. >> reporter: nancy began locking important papers including the girl's passports in her car. >> i went down in february '08 it was awful. i had never seen nancy stressed out before. i never seen her raise her voice in the house. she was just miserable. >> reporter: miserable. stressed. each day uncertain, a painful

struggle, an angry contest. >> she said, this is just, i think, a game to show me how difficult it's going to be. it's his attempt to force me back into this relationship. >> reporter: then, as nancy was preparing to move back to canada and with brad's blessing take the girls, one of those moments on which lives can turn, the arrival from nancy's lawyer of a proposed separation agreement. alimony, child support, private schools for the girls. brad would have to travel to canada for his twice monthly visits. he made no counter offer. just told nancy the move was off. >> he saw what he was going to have to pay and all bets are off. >> reporter: and then, brad got ahold of the girl's passports, found them in nancy's car. they couldn't leave. nancy was trapped too. >> but as the father, it's his perfect right to prevent those kids from leaving. >> yes. it's also a way to say, if i'm doing half the child care, then i'm not going to have an alley moweny issue. >> reporter: to get her away

interest her troubles, fancy's family took her and the girls on the vacation. >> how was it at the end? >> heartbreaking. i had her in my arms at the airport in charlotte and she was sobbing and she said mom, i just want to come home. and i'll never forget that day. >> reporter: it was the last time they saw her alive. and now that she was dead, nancy's family was sure brad had to be involved somehow. but debt tifk danielss knew the demise of a marriage no matter how bitter it had been did not prove murder. there was more work to do. >> statistic says we should key on the husband and we're not going to walk away interest that, but at the same time we're letting the investigation lead us wherever it goes. >> reporter: coming up -- brad cooper comes clean about his affair with nancy's best friend. >> took place in her home, the residence of nancy and myself. in the closet of the master bedroom. >> reporter: when "dateline"

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in the days after nancy cooper's murder, the police chief here in cary, north carolina, tried to calm her jittery town, but her message was, well, curious. seemed to imply her officers knew something more than they were revealing. >> we still believe this is an isolated case. cary continues to be one of the safest places to live in the nation. >> reporter: isolated? how could she know, really?

>> we still have not named a suspect or a person of interest. >> reporter: oh, but nancy's family had. the very day christa learned her twin sister was missing she called brad. >> i asked him pointblank at that point, what have you done? where is she? >> she didn't wait for an answer. she just hung up the phone. then, the day after nancy's body was identified, her family went to court to try to get those two little girls away from brad. >> by 4:00 in the afternoon, we had papers in the judge's hand for temporary custody of nancy's children. >> reporter: the family acted so fast because according to their complaint, brad's behavior was so disturbing. before she disappeared, they had seen emotional abuse. and they were sure she never went jogging on july 12. then after she went missing? >> he was very stunned, aloof with the family and didn't contact anybody and he just didn't want anybody around, didn't want any help.

it was strange enough to be alarming. >> reporter: and so they fear for bela and katie's safety. >> did you think they were in danger too? >> if she was a place to do this, the answer to that was absolutely. >> are we sure that this happened? at the end of the day you have to live with the fact that if we're wrong, then this is way over the line. we did it for the right reason. as a family we decided, we're going to take that step over the line. >> reporter: there was an emergency hearing, and the judge determined that the intense scrutiny brad was likely to face during a murder investigation put the children at risk. in late july the girls went back to canada to live with krista, their slain mother's twin and her husband. brad had not been charged with

any crime. wasn't even a declared suspect and he fought hard to get his daughters back. >> afterwards, i thought about it. >> reporter: which meant three months after nancy's murder sitting for a videotaped deposition, in which brad answered questions under oath about his marriage, his affair and what happened the morning nancy disappeared. so, were police investigators listening? oh, yes, they were. >> was nancy a good wife? >> i would say so, yeah. she was supportive of myself and of the children. very loving and generous. >> reporter: but there were two issues. the trouble with cooper's marriage, one was money. the couple had serious debts. >> this past week i looked at the american express card from january 2007 to december 2007. of that, $27,000 was accredited to nancy's credit card. and mine was $17,000. of that, i think $3,000 or $4,000 was part of our monthly bills. >> reporter: it was to reign in nancy's spending, he said, he put her on a cash allowance. >> how much cash? >> at least $300. >> reporter: but nancy said brad was angry that they didn't have

more money to spend. >> she referred to me as the budget nazi. i'm sure she probably said that once or twice in a heated conversation. >> reporter: the other issue? brad's sexual relationship with nancy's best friend heather. the issue which finally brought the marriage to an end. he called it his indiscretion. >> i had sexual intercourse with heather once. >> reporter: it happened some time at the end of 2004, early 2005, he said. >> and where did this sexual intercourse take place? >> it took place in our home, in the closet of the master bedroom. >> did you initially deny the relationship? >> yes. i initially denied it for approximately one year. >> why? >> i thought that if by denying it would go away and we could remain as a whole family. >> reporter: but when it became time for the family to split, brad said he found the monthly terms of the proposed separation agreement unreasonable. >> child support, medical,

private school, extra activities, you know, kind of added it up and i ballparked it at over $5,000 to $6,000. >> reporter: he also explained why he called off nancy's move back to canada. >> i realized that seeing the girls every other weekend would not be sufficient. >> reporter: and brad gave his account of the hours before nancy went missing. they were at a party across the street friday night. he left about 8:00 p.m. got the girls ready for bed. >> the kids fell asleep about 9:00 p.m. i probably fell asleep soon after. >> reporter: he was awakened briefly about 12:30 when nancy came home. >> when she opened the front door and i heard her come up the stairs. >> reporter: he was awakened at 4:00 a.m. by katie's crying, took her downstairs followed by nancy. >> nancy and i tag teamed off and on, trying to keep her occupied, calm her down. >> reporter: he said he made two trips to the store that morning. on the the second trip nancy called him. >> do you know what time that would have been? >> i think looking at the cell phone records i think it said it came in at 6:40 a.m. >> reporter: when he came back

from the store the second time, katie had calmed down, he said, and nancy told brad she was going for a run. >> i took katie upstairs, went in front of my computer, read some e-mails with katie in my lap. >> reporter: and then, around 7:00, he said, nancy left. >> how do you know that she left the home? >> i'm not too sure if she said good-bye. somehow i knew she left. the door closed or she said later or something. >> reporter: that, he said, was the last time he saw her. three weeks after this deposition, three months after nancy's body was found, in late october, brad cooper was arrested and charged with the murder of his wife. so, was it something he said?

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he was just the right sort of guy when she found him, bright, quiet, stable, this computer genius so skilled a national powerhouse had sought him out. now, brad cooper was on trial for murder.

>> at this time we are ready to have the opening statements. >> reporter: it began this past march, 2 1/2 years after nancy's death. >> nancy cooper never went for a run from her house on july 12th of 2008. >> reporter: the prosecutors howard kum, amy fitz and boz had their own idea of what happened to nancy the night she disappeared. >> we think she came home from this party and said some things in front of him that might have upset him a little bit and he choked her. >> reporter: killed her then, their theory goes, put her body in the trunk of his car, drove to that drainage ditch, returned home to manufacture an alibi. why? she started with the shredded marriage, brad's affair, cutting off nancy financially, stopping her move back to canada. she was, testified nancy's friends, increasingly desperate. >> she said he's breaking me. i don't know how much left i have to fight.

>> she told me when she slept at night she slept with her jeans on and the keys in her pocket with the children and the door locked. >> reporter: he never beat her. it wasn't physical, said the prosecutors. but he used financial power to exert absolute control. this, they said, was a form of domestic violence. >> she was in this abrasive, rough relationship at that point. he trapped her. he controlled everything about her life. >> reporter: wait a minute. nancy's allowance, remember, was $300 a week. would a jury think that was evidence of abuse? >> how do you tell a jury that he's depriving her. >> it's difficult. the facts still remain there are these signs of control emanating from that cooper household. >> it doesn't matter whether it's $1,000 a week or $10 a week. the fact of the matter is, is that it caused friction between the two of them. >> reporter: and so the jury heard about that last week of nancy's life, the week of war with brad.

with nancy's father on the stand, prosecutors played a phone message nancy left her parents after she returned home from that vacation with her family. >> the house was so dirty. there were ants infesting on the table when i got there. >> as that last week went on, the fighting escalated. on friday, her friend testified, nancy was shaking with anger when she revealed brad withheld her allowance that day because she earned her own money painting a house. >> did she tell you what kind of day this was? >> this was an "the hate brad" day. she said three times that day, i hate you brad cooper, i hate you, i hate you, i hate you. >> describe your demeanor for us if you would. >> she clenched her fists and spat the words out. >> reporter: diana lived across the street. it was her party that friday at

which brad and nancy fought openly, she said. >> her tone was angry but also there was a tone of you're an idiot. >> reporter: brad went home with the girls answered 8:00. nancy stayed on, bitterly complaining about brad, to strangers like donna lopez. once in a while, said donna, nancy nervously looked across the street to her own house. >> how did you feel when you left that night? >> i was very worried for someone who i didn't know well. i thought i met someone really, really nice and told my husband, something really bad is going to happen over there. it's really bad. >> reporter: so, when nancy disappeared, her friends' eyes all turned to brad. after all, they knew about the conflict and jessica adam knew nancy was supposed to be at her house at 8:00 that saturday to paint. when nancy didn't show up, she called the police. >> i was very concerned. i had seen brad in my house and he was agitated that week. related to the painting. >> reporter: as a marriage gone bad, it's hardly proof of murder. nor was brad's conspicuous

absence from her memorial service, nor his apparent lack of interest or cooperation as the police sought in the murder investigation. these were suspicions. but there was no physical evidence linking brad to the crime. the prosecutor would say it was because he cleaned the house. he covered his tracks well. but there it was. what was the best evidence against brad? ironic, perhaps, given the defendant's particular expertise. >> we knew we had this fabricated alibi we needed to address. >> reporter: the issue was the phone call the morning nancy disappeared. brad's cell phone registered a call from home at 6:40 a.m. when he went back to the store. proof, surely, that nancy was alive at 6:40. unless, that is, unless brad placed the call himself. brad, the world-class expert in internet phone technology.

>> if anyone could do that, it was the defendant. ultimately, he had the potential to make that phone call. >> reporter: in testimony that was, frankly, mind numbing. >> that leverage is something called either tappy or j tappy. >> reporter: an expert from cisco, brad's former company, explained about ten different ways someone as accomplished as brad could have remotely made that call. >> the main ways to do it are using a computer where you can program something into your computer and delay it so that a phone call can be made from your computer from the computer's modem. >> reporter: to do that, brad needed a certain router. one prosecutor said conveniently disappeared from the cooper home. >> we know he had this router. >> reporter: in fact, said the prosecution, this cisco chat log proves brad borrowed that router, the 3825 it's called, took it home, months before the murder. >> you know that defendant had one of those two 3825 routers? >> that's correct.

i only had two. >> and you never got that 3825 router back? >> no, sir. >> cisco doesn't have it back, where did it go? we know it was never returned. >> reporter: but it was brad's own computer examined by the fbi which coughed up the most accusing evidence of all. evidence he had already lied under oath. >> the kid fell asleep about 9:00. i probably fell asleep soon after. >> reporter: in his deposition, brad said she was asleep with his daughters when nancy came home from that party friday night. but brad's computer said otherwise. he was on-line, until about midnight when nancy came home. >> he's been awake on his computer and when she comes in shortly after midnight we think they argued and that a fight ensued and that's when he strangled her. >> reporter: and then? the closest thing the prosecution had to a spoking gun. a google map search. brad typed in the numbers 27518 the zip code for cary and zoomed in to the exact location where nancy's body was found. when did he do this?

1:15 in the afternoon on friday, july 11th. the day before nancy went missing. >> this is the most pointed piece of premeditation, if you will. >> reporter: but, proof of intent? maybe. maybe not. it wasn't much of a search. it lasted just 41 seconds. >> he didn't look anywhere else. generally you search a whole bunch of different places and this is one place and it's only 41 seconds long. >> i don't think it would take very long if you look at the mapping, you immediately recognize this desolate area, this beige area in a sea of green and then zoom into it, zoom into it, zoom into it and see where it is. >> reporter: of course, every prosecution has its flaws. and this one, maybe said the defense, they didn't have the right man at all. and maybe they didn't know nancy so well either. she, too, the defense suggested, had been unfaithful, and they

found a witness to prove it. >> she began taking her clothes off, i took my clothes off. >> reporter: but did that have anything to do with the day she disappeared? you wouldn't accept an incomplete job from any one else. why accept it from your allergy pills? flonase relieves your worst symptoms including nasal congestion, which most pills don't. flonase helps block 6 key inflammatory substances. most pills only block one. flonase. money managers are pretty much the same. all but while some push high commission investment products, fisher investments avoids them. some advisers have hidden and layered fees. fisher investments never does.

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the idea that they're in a bad marriage, that they're contemplating divorce, it gets you to the point where you say, i need to take a second look at this. >> reporter: this is howard kurtz, defense attorney, and here's what he thought about the murder case against his client, brad cooper. >> you need actual evidence to convict and actual evidence is something that they did not have. >> reporter: no physical evidence, said defense attorneys kurtz and robert trankle to tie brad to nancy's murder. the awful scenes from the cooper marriage the jury heard no

witness from either side had seen brad physically violent toward nancy. for the $300 a week allowance there was a reason, the defense argued. remember the couple had serious debt. the defense offered contrasting scenes of the cooper marriage from another set of friends. >> people who had known the couple for years, did not jump on this bandwagon to paint this as an abusive relationship. >> reporter: remember that "i hate brad" day, the day the prosecution said the marriage hit its boiling point. on that very day, said laura hiller, nancy was making plans for saturday night, the day she disappeared. >> she wanted my husband and i to come over and play sequence with her and brad. >> was that a game you had played with the coopers before is this. >> nancy introduced us to that game. >> reporter: when nancy's friend jessica testified they had plans to paint her house at 8:00 saturday morning she had to be have been mistaken, said the defense, because nancy knew brad had a tennis game at 9:00 a.m. with mike hiller. >> i specifically sought out nancy to make sure it was okay with her.

>> did it indicate she had any other plans? >> there was talk she was going to jog and she would be back by then. >> reporter: there were people who claim they saw a woman they believed was nancy running and it was proof, the defense says, that she was alive that morning. >> she was about 5'9", good shape. >> reporter: this witness said she reported her sighting to the police after she saw nancy's missing poster. >> how is it that the next day when you saw the flyer, you believed it was her? >> because she was so close to me and she had an elongated face. that's what drew my attention. >> reporter: she wasn't the only one. this man said he got a 30-second look at her as he was driving to work. >> i saw a lady jogging on the right-hand side of the road. jogging towards the bridge. >> but did the police follow up? not for a long time, said these witnesses. >> they ignored everybody that believed they saw nancy for three months. >> reporter: those suspicious

vans, said the defense. >> it was clear that the police had focused on brad to the exclusion of other people. >> reporter: it wasn't just brad who had been unfaithful. implied the defense. could someone else have wanted to silence nancy permanently? someone suggested the defense like john pearson who at first didn't tell the police about an indiscretion with nancy. he said he held back to protect his family. it happened after a very tipsy halloween party back in 2005. >> she began taking her clothes office, i took my clothes off, and we, i believe, started to have sex. i believe we stopped and got dressed and decided to never speak about it again. >> it seemed to observers as if you two were somehow blaming the victim? you were looking for other people she may have had relationships with. why was that important?

>> the reason that people looked to the spouse first, is because affairs of the heart frequently lead to crimes of passion. so, anyone with whom she had a relationship, should be the subject of a police investigation. >> reporter: and there may have been other secrets, the defense charged, clues to nancy's life they'll never know because, and this was big, a cary detective erased the contents of her blackberry accidentally, said the prosecutors. nonsense, said the defense. >> it's not something that happens accidentally. >> reporter: a prime example, the defense said, of shocking allegations that the police investigation was dishonest. why would the police have any motivation whatsoever to get rid of evidence in this case? >> not only did they start with an eye towards building a case

against brad, they also started with an eye toward attempting to preserve nancy's reputation. and that phone would carry e-mails, text messages, pictures, videos. >> you think it would have been exculpatory evidence for your client? >> i don't know what it was. because we never did get in that phone. >> reporter: and that call saturday morning from brad's house to his cell phone, the one the prosecution allege brad actually made himself with that now missing router. they claim that he checked out a router and never returned it. >> the question is, did he generate a phone call. not did he have the technological skill. they also took photographs of the house. they searched the house. and they have not once introduced any evidence that the router was in the house.

>> reporter: hard drives don't lie. or do they? that was the question the defense raised when it came to those apparently damming results of the fbi's search of brad's computer. >> you're talking about a computer that we know was tampered with. >> you're alleging what? >> i'm not alleging. i'm stating as fact the computer was tampered with. there were significant anomalies that we found in the computer itself. >> reporter: meaning, he says, that brad's computer was hacked. the 41 second google map search was planted. the prosecution had no smoking gun. so you're saying he didn't even search for that map? >> that's right. >> somebody else put it on his computer? >> yes. >> an fbi agent had testified

that he saw no evidence of tampering, but the defense said, it had experts who didp. two of them. both of whom wrote reports. but, trials have referees and in this case, the judge ruled that neither one of those defense experts could testify about tampering. one, said the judge, wasn't sufficiently qualified, the other brought in too late in the trial. but, even if they had testified, there was one question they couldn't answer. if there was a hacker, who was it? >> i can tell you that police had access to it. i can tell you that anybody within wireless range had access to it. >> what possible reason would the police have to put that map on his computer? >> i can't say that the police put it on the computer. i don't know who manipulated the computer. what i can say is, that a possible reason is if you believe somebody's guilty and that you don't have any evidence against them, well, it's perfect evidence. >> reporter: could those 41 seconds put brad cooper in prison for the rest of his life?

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for two long months attorneys for both sides hammered at the question, what happened to nancy cooper? the defense charged the police more than dropped the ball.

their investigation was dishonest. the erasing of nancy's blackberry, for one thing, had to be intentional, said the defense. nonsense, applied the prosecution. besides, they claim, they already found what they needed from that phone through other sources. >> we lad her phone records. we knew everything she had done. we had the billing to know how much texting she did or didn't do. we knew her friends. >> the idea the police might have inserted the google map search on brad's computer, they couldn't have, said detective daniels. >> none of the people that work for me or work in the department would have had the knowledge to go in and do something like that. >> reporter: the defense charged that police ignored those possible sightings of nancy and mysterious vans for months. >> the defense was thinking that jury wasn't listening. the police indicated that they followed up with every one of those people. >> reporter: as for john pearson, whose indiscretion with nancy should have made him a suspect, at least according to the defense, he had an alibi.

on that friday night, pearson spent the night with heather. very same woman behind brad and nancy's breakup. >> at the beginning of the case -- >> reporter: still, as the long trial finally wound down, the defense hammered home its claim that the police and prosecution bought into a whispering campaign when nancy's friends against brad. >> it made it easier for them to simply let the gossip about brad became their reality, even when the facts and the evidence did not fit it. and now, the police department and the prosecutors are willing to send an innocent man to rot in a done begun in essence for the rest of his life. >> reporter: but there were facts said the prosecution to send brad cooper away. >> the defendant googled where he was going to place his wife's body. fact, the router that could help him automate a phone call is now

missing. fact, nancy cooper never left that house the morning of july 12th. >> reporter: so, the jurors adjourned to deliberate. guilty of first-degree murder, second degree or not guilty? and nancy's family, having listened to weeks of confusing circumstantial evidence, worried. >> if i was hearing this for the first time, would i feel comfortable sending someone to prison for the rest of their life? >> reporter: the jury stayed out for two days and then -- >> has the jury reached a unanimous verdict? >> yes, sir. >> the verdict of the jury reads, we the jury by unanimous verdict find the defendant, bradley graham cooper, to be guilty of first-degree murder. >> i cried for hours. >> i cried for hours. relief, yes, it's over. there's a conclusion and it's justice for nancy. now we can all go home. >> reporter: and brad?

>> obviously brad was upset, but he knows and feels this is not over. >> reporter: brad will appeal, based possibly on the judge's ruling excluding his expert computer witnesses. certainly these attorneys have strong views about the damage that ruling may have caused. >> it was crippling. >> reporter: nancy, there's a bench in a park, the place she once ran, her adopted town's way of remembering. the cooper girls, bela and katie, are growing up in canada with nancy's twin sister krista and her husband jim. >> they're doing great. it's like every other normal little toddler and little kid. >> reporter: their cousins were with them the day we came to call so seven of the little girls scampered about, their pleasure infectious.

for the adults, bittersweet. >> it's sad nancy is not here seeing it. >> absolutely. that's the tough part for me. >> what do they understand about mother and father? >> well, what we've told them is that mommy nancy was killed by a bad man and that she's in heaven. and the man went to prison. >> brad? she knows this may sound weird. >> i told them he's traveling because he worked so much, it's actually pretty easy and plausible and that he's in a tent and has no phone. >> you know they'll ask some day. >> they will ask when they're ready and us, as a family unit, will sit down with them and it tell them what happened one day. >> reporter: tell them the tragic story of a man and a woman who sank in the undertone of what once was love. >> we got an outcome that nancy disde serves, but it's also not a winning hand for anybody. and brad lost his life as well. there's many things that were lost, lives that have been forever changed.

>> that's all for now. i'm lester holt. for all of us at nbc news, thanks for joining us. i can't believe that your baby's lying there lifeless. >> she was everything to me. she was so sweet to everybody. >> state troopers said bonnie had died in a hiking accident. >> they said she fell off a cliff. her mother said they were wrong. >> i was screaming to them, these are defensive wounds. >> no witnesses, no weapon, nothing left behind but a stranger's dna. >> we no longer have some accidental death. this was a homicide. >> they had no suspect, but for years