space, and steve's t-shirt shop wants to bring on more help. with the comcast business 5-year price lock guarantee, they can think more about possibilities for their business and not the cost of their internet. it's five years of gig-speeds and advanced security. all from the company with 99.9% network reliability. get the 5-year price lock guarantee, now back for a limited time. powering five years of savings. powering possibilities™. . comcast business. i'm craig melvin. and i'm natalie morales. and this is "dateline." en. her husband, the air force captain, and the staff sergeant, her rendezvous man.

he was a playboy himself. craig melvin: one man too many. then, suddenly, there was one man less. it wasn't like bang, bang, bang, bang. it was, bang, pause, bang, pause. which sounds more like what? execution? you could take it that way, yes. craig melvin: a cold-blooded killing. but who pulled the trigger? did jealousy drive someone to murder, or did she? coy brewer: michelle theer was a brilliant, cunning, ruthless woman. hello, and welcome to "dateline." the story you're about to see centers on a death of a military man, thousands of miles from a battlefield-- a dedicated officer who survived war zones only to be caught in the crossfire of a lovers' triangle. here's keith morrison.

[computer whirring up] [typing] keith morrison: what was she thinking when she went to the computer, when she typed in those five little words? did she not understand where those little words might lead? michelle theer (on phone): i need an ambulance! dispatcher (on phone): where are you at? michelle theer (on phone): i don't know! dispatcher (on phone): ok, what's your name? michelle theer (on phone): i'm michelle. keith morrison: michelle theer was, no doubt about it, dissatisfied. here she was-- young, successful, attractive, and yet. it wasn't exactly boredom that was eating at michelle. after all, she was just starting a new career as a psychologist, often counseling troubled couples. melissa stoddard diaz: she was relatively new with her license. i think that was her first real job. keith morrison: of course, michelle would have laughed at the idea that pretty soon now, events would propel her to such notoriety,

that newspaper reporters like melissa stoddard diaz would be poking around in her past. michelle, from everyone i've spoken to, wanted to be somebody, and really worked hard to get to where she ultimately got her degree and became a professional. keith morrison: but then, michelle, even at an early age, always seemed confident about getting what she wanted. she was just 16 when she started dating marty. marty theer was a couple of years older, worldly, bright, friendly, had big plans. he wanted to be an astronaut. he went to the air force academy. [wedding processional] she was 20 when she married him at the academy's famous chapel outside colorado springs. man: marty, you may kiss your bride. keith morrison: this was back in 1991, when marty was all she ever wanted, long before she talked to that psychologist, agreed to record,

for the record, her thoughts about the weird events yet to come, and those happy days with marty, too, of course. michelle theer (on recording): we did everything together. he treated me really well. i just thought we had the perfect relationship. we were best friends. keith morrison: he was the dashing young officer back then, she, his lovely bride. the future she imagined-- an endless honeymoon in which marty's air force career would take them to exotic destinations all around the world. she just didn't imagine that world would be unromantic air force outpost in oklahoma and alabama and florida, and finally, fayetteville, north carolina. they came here in 1999. marty was captain theer by then, flew one of those huge c-130 cargo planes. all that time alone-- not too easy on a marriage, as she revealed during those tape-recorded interviews with psychologist dr. debbie layton-tholl.

michelle talked about a few problems in the marriage-- primarily, growing apart over the years. marty was away for extended periods of time. she had a hard time with that. it was getting more difficult for her. she was lonely. keith morrison: sometimes he was gone for months. and when he finally did come home, military families have come to know that adjustment period all too well. they bickered. they argued about her housekeeping, his job, about having children. he wanted them, she didn't. she was worried she'd be stuck raising them by herself in a town where she was already miserable and lonely. michelle theer (on recording): here i was in fayetteville-- "loserville"-- and had nobody to hang out with, nobody i could pick up the phone and call. keith morrison: that, actually, is about the time it started. harmless, really, just a few keystrokes. see what might happen. goes on all the time these days on the internet. "sexy brunette seeks rendezvous man."

and before long, her internet inquiry got a response-- from him. his name was john-- john diamond. debbie dvorak: john loved women. john was a ladies' man. john always had girlfriends. keith morrison: so debbie dvorak, john's kid sister, could certainly see her brother responding to a solicitation like michelle's. debbie dvorak: my brother's got a great personality. he's an attractive guy, and his personality makes him that much more attractive. keith morrison: then, a few days after meeting online, they met in person at a local restaurant. michelle theer (on recording): he was charming. he was funny. talked about movies and music, and things that me and marty didn't talk about. keith morrison: john diamond was an army staff sergeant, based at fort bragg and trained as a sniper, highly regarded, decorated, had been in the service since he was 18. by all accounts, he was a good soldier. but he was a playboy himself. he had been married once before

and had a child from his first marriage. and he left the first wife and married, and they had a son together. keith morrison: michelle didn't know that john was still married. but maybe it didn't matter-- at least not then. she loved the sex, the attention, the excitement. michelle theer (on recording): he was very attentive. he was very affectionate. he was very adoring. yeah, it felt great. what made her so desirable to him? i think it was just the sex. that was what he was obsessed with. he was smitten with having sex with her. keith morrison: for michelle, well, it was more lust than love. debbie layton-tholl: she felt that the affair did not take away from the fact that she loved marty. she said he was the love of her life, and that she never loved john diamond. keith morrison: and marty-- he was in the dark, of course. when michelle told him their marriage was in crisis and they needed to see a counselor-- michelle theer (on recording): he wouldn't agree with counseling, and i moved out.

he was shocked. keith morrison: michelle got her own place and spent much of that steamy fayetteville summer with john diamond. michelle theer (on recording): he was so attentive. he would rub my feet for five hours if i wanted him to. keith morrison: diamond was apparently nuts about michelle. never met anyone like her before. she challenged him in ways that he'd never been challenged before. keith morrison: paul woolverton is a reporter with "the fayetteville observer." she was strong and intelligent and exciting for him. keith morrison: but was he enough for her? apparently not. because after three months on her own, michelle went back to marty. she felt that the marriage could survive, despite everything that had happened-- that they could make it. keith morrison: so john and michelle's six-month affair seemed to be off. but then, a few weeks later, it was apparently back on. the two traveled to the tropical island of saba, where michelle interviewed for a job at a local university,

and later that fall, a romantic rendezvous at a raleigh hotel, where they celebrated michelle's 30th birthday. but michelle, as she would later tell the psychologist, insisted it was just a relapse. michelle theer (on recording): i knew that i loved marty, and i knew that i wanted to make it work in my heart. keith morrison: but john diamond was devastated. or so said michelle. michelle theer (on recording): he said specifically, i'm going to kill myself. i can't live without you. you can't do this to me. i'm going to go drive my car off a bridge. it was awful, said michelle. diamond kept calling, made a scene at her office in front of some students she taught-- even threatened to call marty and tell him everything. so nearly a week after that romantic night in raleigh, michelle says she met john at a local restaurant to end the affair, gently but for good. michelle theer (on recording): we had the whole talk--

yes, we can only be friends. this can never happen again, never, never, never. he seemed very calm, very rational. keith morrison: so now, it was december-- time for peace and joy, christmas parties-- one in particular at which the spirits flowed and the fuse burned down to its explosive end. somebody was about to die, and somebody else wasn't taking any chances on missing. craig melvin: coming up. paul woolverton: it wasn't like bang, bang, bang, bang. it was bang, pause, bang, pause. keith morrison: which sounds more like what? an execution? you could take it that way, yes. craig melvin: when "dateline" continues. have you always had trouble with your weight? same. discover the power of wegovy®. with wegovy®, i lost 35 pounds.

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keith morrison: here in the heart of the american bible belt, on the fringe of vast sprawling army and air force bases, like a patient, accommodating landlord, is fayetteville, north carolina. imagine most of a suburban strip mall devoted to strip clubs, and a downtown, which is charming, elegant even, that has seen about everything. it's an old town, fayetteville. that tower marks the spot where

north carolina ratified the federal constitution back in 1789. i'm standing on what was a slave market. sherman fought battles here in the civil war. but now, it's a military town, and 160,000 acres back there is the army's fort bragg, where soldiers prepare to go to war. nestled up beside that is pope air force base-- two institutions, two professional military men, one woman. and that woman, michelle theer, now found herself caught between her husband, marty, the air force captain, and her former lover, army staff sergeant john diamond, who just wouldn't go away. michelle theer (on recording): i told him, i don't want to leave my husband. i never told him, i love you. i never said i want to be with you. i mean, i think i was pretty straight-up. keith morrison: so now, with the holiday season in full swing and a new commitment to her marriage, michelle and marty were on the road to raleigh for a night out.

traveling with them was another couple from her office. melissa stoddard diaz: they had gone to this christmas party that she specifically asked her boss if marty could go. keith morrison: it was sedate, by office party standards, and over early, since marty had to fly first thing in the morning. so now, it was 9:30 pm. marty, michelle, and the coworkers prepared to leave the restaurant. then, an interruption-- michelle excused herself, made a brief phone call, out of earshot of the others. then, the drive to fayetteville-- one hour. they dropped the other couple at michelle's office, then left for home, stopped on the way for gas. and then, sitting at the gas pump, michelle told marty she'd forgotten something at the office. michelle theer (on recording): we ended up turning around and going back to the office to get some stuff that i needed so that i could stay up and work that night. keith morrison: marty parked behind the office building. michelle walked up an outside staircase, disappeared inside, marty waiting in the car.

apparently, he got impatient, headed up the stairs to check out michelle, and that's when it happened. she found him, she said, at the bottom of that outside stairway. she could see the blood. she ran to the nearest store, called 9-1-1. michelle theer (on phone): (crying) i need an ambulance. somebody shot my husband. dispatcher (on phone): somebody shot your-- michelle theer (on phone): 2500 raeford road. dispatcher (on phone): somebody shot your husband? michelle theer (on phone): i think so. dispatcher (on phone): where are you at? michelle theer (on phone): i don't know. dispatcher (on phone): ok, what's your name? michelle theer (on phone): i'm michelle. [siren blares] keith morrison: within minutes, fayetteville police and paramedics arrived, and they found michelle cradling her husband in a pool of blood. but it was too late. marty theer was dead. he was just 31. because marty was an air force captain, military investigators were soon on the scene as well as police, making this a joint investigation with the fayetteville pd. both teams were eager to speak to the only known

witness, michelle theer. office of special investigations agent, vince pastillo-- she said she heard what sounded to her like three bangs of a car backfiring. did she tell you what she did at that point? she then opened the door and noticed that her husband was laying at the bottom of the stairs. keith morrison: she told them she thought she saw somebody moving in the bushes near the stairway, but she wasn't sure. initially, i think police were looking at perhaps a robbery of some type. keith morrison: detectives combed the parking lot, surrounding area, but found no one on this cold, dark december night. there was a man who lived behind the office building, who heard the shots fired, who later said that he said, somebody's getting murdered out there, because of the order in which the shots were fired. they were very calculated. it wasn't like, bang, bang, bang, bang. it was, bang, pause, bang, pause--

a space between each of the five shots. which sounds more like what? an execution? you could take it that way, yes. keith morrison: at the top of that stairway were a few clues. bullet holes sprayed in the wall, sequins from marty's holiday suspenders littered the landing. looked like he was at the top of the stairs, shot from down below. i think that's what made him roll down the stairs, and the final shot was to the back of his left ear. the kill shot. the kill shot. close range. keith morrison: they found shell casings in the parking lot-- appeared to be from a 9-millimeter handgun. but there were no fingerprints, no footprints, no useful dna. but investigators did find marty's wallet still on him, complete with cash and credit cards. marty theer was not robbed. the other thing was that it was a very, very cold night, not a night where a prowler would be out on the streets just looking to find someone. it made it very suspicious.

keith morrison: investigators couldn't imagine who would want to kill such a wonderful man like captain marty theer. but of course, out in this dark parking lot, they didn't know any of what you know-- not yet, anyway-- assuming what you've heard so far is the real story. and as you'll see, the question of what was true and what wasn't could be very tricky indeed. michelle said she'd gone back to her office, because she'd forgotten something. so what took so long? coming up-- greg butler: they found a candy wrapper that had been opened and in the trash. it was almost like a scene, where she had just gone upstairs and sat and waited for a few minutes. craig melvin: for what? when "dateline" continues.

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keith morrison: it was a week before christmas 2000, and fayetteville was aglow-- but not everywhere with the lights of christmas. and a few hours after air force captain marty theer turned up dead in the parking lot of his wife's office building, the news was out, and it was big. michelle theer-- now, marty's grieving widow-- told the police she was inside her office looking for a book when she heard someone firing outside. by all accounts, it was an assassination.

greg butler was a deputy district attorney in fayetteville at the time. greg butler: if somebody were to kill marty there that night, there was no evidence of any robbery. there was no evidence of any other thing going on here. keith morrison: though inside michelle's office, what they found seemed, well, a little odd, maybe. greg butler: --that she'd gone to the bathroom. the toilet had not been flushed. they found a candy wrapper that had been opened and in the trash can. it was almost like a scene where she had just gone upstairs and sat and waited for a few minutes, because obviously, finding a book wouldn't take very long. keith morrison: strange, hard to know what it meant, if anything. as dawn approached, michelle was allowed to go home. and later that morning, her boss arrived, so the cops talked to him, too. during that interview, it came out that she was having marital problems and was having some extramarital affairs. keith morrison: funny. michelle hadn't mentioned anything about that. so detectives went to her house to follow up. and sure enough, michelle did admit

having an affair with staff sergeant john diamond. michelle also said she hadn't spoken to diamond in two days, but when pressed, she remembered trying to call him, unsuccessfully, just before leaving that christmas party-- about 90 minutes before marty was murdered. so detectives decided to check their cell phone records and discovered-- vince pastillo: they'd been calling each other regularly-- minimum, 20 times a day. keith morrison: and now, detectives paid a visit to john diamond, who freely admitted having a sexual relationship with michelle, but claimed she was just one of many ladies in his life. and as for the night of the murder, he had an alibi. he was home with his family, watching a movie. still, michelle must have harbored some sort of suspicion about john diamond, who was now a person of interest. not long after the murder, as she told detectives and that psychologist, she went to see diamond to conduct her own investigation,

find out what he knew about marty's death. michelle theer (on recording): i said, do you know anything about this? do you know anybody who had anything to do with this? he said, no, i would never do anything to hurt you. i know how much you loved him. i believed him, and he looked so trustful. keith morrison: mind you, as police were soon aware, michelle had many opportunities to question her friend, john, after her husband died. greg butler: there were witnesses showing that he'd parked, down a little side street, and then walked through their yards, going into the back door of her house. he couldn't stay away from her. oh, yeah, he was going in there, and then staying all night. keith morrison: not commonly the way widows grieve-- spending the night with the person of interest in her husband's murder. but michelle told psychologist dr. debbie layton-tholl she needed support from someone, anyone. debbie layton-tholl: as she felt more alienated from family and friends, and more threatened by the police, the only person in her life

that was willing to be there for her was john diamond. michelle theer (on recording): i knew that i was depressed, and i was getting more and more depressed. and i think i went to john for comfort. keith morrison: in fact, just a few weeks after marty's murder, michelle and john drove to florida for a long weekend. michelle wanted to see a former professor for grief counseling, she said later, while diamond stayed with his sister, debbie. debbie dvorak: he acted as if nothing was wrong. because he knows he didn't have anything to do with it. he didn't shoot him. keith morrison: so who did kill captain frank martin theer? was it possible john diamond actually executed his romantic rival? he may have had a motive. police were very suspicious. but the physical evidence was, frankly, rather weak. so detectives kept digging in the arcane world of phone records-- boring, but sometimes revealing. and one telephone number in particular caught their attention--

a call from diamond to one of his army buddies at fort bragg. so we asked him if diamond had any access to any weapons. he said that he loaned diamond his personal pistol. keith morrison: which just happened to be a 9-millimeter beretta pistol-- the same kind of gun that killed marty theer. greg butler: john diamond had actually borrowed the gun from him. during the time frame of when the murder occurred, he had-- john diamond had possession of it. keith morrison: detectives were now convinced that diamond not only had access to a gun, but maybe even the actual murder weapon. did he still have it? well, apparently not. because just a short time after cops went to the home of diamond's army buddy, asking about that gun, diamond made a phone call to fort bragg and reported that his car, which he claimed to have left in the base parking lot, had been broken into, and one of the things stolen from it

was a 9-millimeter handgun. vince pastillo: when we got there, the passenger door had already been opened, and there was a pile of glass sitting next to the rocker panel on the passenger side. but if you look on the inside, there was very little glass. what did that tell you? he had the door open when he broke the window, and then tried to make it look like it was broken in. keith morrison: a bogus break-in? military police sure thought so. john diamond was arrested for admitting that he brought an unregistered gun on base. clearly, diamond was now the prime suspect in the murder of captain marty theer. but was he really the killer? craig melvin: coming up, a secret about john and michelle's steamy affair becomes very public. debbie dvorak: she was taking him to these sex clubs and saying, it's ok, go. if you want to have sex with her, that's fine. and he just-- wow, ok.

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i am frances rivera with the top stories to a major power outage hit puerto rico early tuesday, leaving much of the island without electricity at of new year's eve celebrations. power is slowly being restored to according to the white house, president biden spoke with the president there to discuss the widespread power outages across puerto rico and offer assistance. now back to dateline and happy new year. gun onto a militar -- the same type of weapon used in the fatal shooting of his lover's husband. he was now investigators' prime suspect,

but they needed more evidence. continuing with our story, here's keith morrison. keith morrison: a few weeks after the murder of captain marty theer, a fayetteville police detective named ct williams was asked to have a look at a couple of computers seized from michelle theer's home, see if they might contain any clues. ct williams: i just was looking for documents or text messages or emails. keith morrison: like an onion, he peeled back the layers of text, which, though they'd been deleted, reappeared under his expert touch. boxes of deleted documents-- 88,000 of them-- buried deep inside michelle's hard drive. and out spilled some of michelle's most intimate sexual secrets. ct williams: she seemed to be seeking affairs with a number of people over time. she was looking for an alternative lifestyle. she was seeking a partner and escort for sexual swinger-type clubs. keith morrison: that would be carolina friends, a swingers' club. it boasted more than 10,000 members.

and within michelle's lengthy list of emails, detectives also discovered that not-so-innocent inquiry she typed, seeking a rendezvous man. that was john diamond, of course, who replied, and who, the email trail revealed, quickly joined michelle in the lifestyle. debbie dvorak: she was taking him to these sex clubs and saying, it's ok, go. if you want to have sex with her, that's fine. go, i'm fine with it. and he just-- wow, ok. keith morrison: but as investigators sorted through the sexually charged email, they could plainly see a story as old as time. john diamond fell head-over-heels in love with michelle. ct williams: he was her little puppy to be controlled any way she wanted to control. he was like the child in the relationship. whatever she wanted was-- he was at her beck and call. keith morrison: hundreds upon hundreds of lurid, lovesick emails-- john diamond appeared to be a man obsessed. "i can't wait till you come back, so we can take care of each other.

you know, sex, sex, sex, and of course, more sex. i know that we're meant to be together and are kindred soulmates." "i will always love you, no matter how you've hurt me." well, you could tell it was now changed from a sexual relationship to completely, totally enamored with her, in any way you can imagine. and he was getting desperate to be with her. he wants to be with her. his plans were to be with her. he was willing to do anything to keep the woman he's totally in love with. keith morrison: anything? perhaps even kill the man who stood between him and michelle? greg butler: she was beginning to set him up. she was playing his emotion. she was pushing him away, kind of. she was pushing him away in some ways, but without really completely pushing him away. push-pull. i think she was manipulating him at that point. keith morrison: manipulating him into murdering her husband? but why would she want to do that? there was a $500,000 life insurance policy that had been taken out in 1999 on marty theer. keith morrison: and the sole beneficiary-- michelle theer.

john diamond's family was outraged at such a theory. they were convinced michelle typed all those emails and sent them to herself to steer investigators away from her and to diamond, so he'd take the rap. he never once expressed a love feeling about her to me. so unless you come to me with a handwritten letter that he was obsessed with her, i'll never believe that. but how do you know that? because he told me. he did not want to marry her. he did not want to spend the rest of his life with her. keith morrison: according to debbie, it was michelle who was obsessed with john, and never more so than when she gave debbie two wedding rings to take to her brother, who was, by this time, locked in the brig. i think maybe she was obsessed with him in the point that she couldn't control him, that she couldn't control the situation. she wanted to control it. and if she gave him a wedding ring, and he wore it, wouldn't that give her all kinds of reason to claim that he would do anything for her,

including kill her husband? that could be. i don't know. what i got from him after he was arrested was, he didn't want anything to do with her. nothing. keith morrison: but with or without michelle, john was in big trouble. so he lawyered up with prominent fayetteville attorney coy brewer. i believe that he was an innocent man wrongly accused, that any rational interpretation of the circumstantial evidence is consistent with sergeant diamond not being the shooter. keith morrison: but military investigators were convinced diamond was the triggerman, and decided to quickly proceed with their case against him. and michelle remained free. and what did she do? well, she left town. i think she planned to kill her husband a long time ago. i think she waited and researched, and waited for that right person that would look and fit the part to pin it on. keith morrison: if that was true, michelle's plan was working perfectly.

because in a few short weeks, john diamond would be on trial for murdering her husband. craig melvin: coming up, the prosecution's case against john, and the defense's case against michelle. coy brewer: michelle theer was a brilliant, cunning, ruthless woman who wanted her husband dead. craig melvin: when "dateline" continues.

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askkeith morrison:day. in the dead center of fort bragg, north carolina, is a nondescript, red brick building. this is where army staff sergeant john diamond found himself a prime suspect in the murder of air force captain marty theer. melissa stoddard diaz: military justice is much swifter than civilian justice. so he goes to the article 32 hearing, which is like the grand jury. they immediately find cause, and they charge him. keith morrison: and nine months after the murder, in a small fort bragg courtroom, diamond went on trial before a military jury. melissa stoddard diaz: diamond was very, very cocky at the beginning. he would laugh and joke with reporters in there. he was just so sure that he was going to be acquitted. keith morrison: but john diamond wasn't the star of his own trial. michelle was. she was free as a bird then, though still under investigation by fayetteville civilian homicide cops.

and here she was, called to testify at her former lover's military trial. melissa stoddard diaz: and she shows up. her hair is now, like, a red color that she's colored it. she's lost a bunch of weight, and she's got a gaggle of media following her into the building. keith morrison: it was all image, no substance. michelle took the stand, but took the fifth. the prosecution's case against diamond-- its accusation was simple. driven by his obsession for michelle, he conspired with her to kill her husband by borrowing the gun, arranging to be in a position in that dark parking lot, waiting until marty theer had placed himself in the kill zone at the top of the staircase outside michelle's office, and fired the five shots that killed him. as for diamond's alibi, that he was home with his wife watching a movie, that now-ex-wife came to court and told the jury that the evening wasn't quite like that. halfway through the movie, his phone rang,

she said, and suddenly, he was gone. and what's more-- melissa stoddard diaz: her mother heard him come home in the wee hours and wash clothes. keith morrison: true? maybe not, said defense attorney coy brewer. her story changed after she talked to police. coy brewer: she was afraid of the government. keith morrison: had she been pressured? besides, said the defense, there was no dna, no footprints, no fingerprints to prove diamond shot marty theer. and any way, diamond was a trained sharpshooter, but the shots that felled marty were sloppy, most of them badly aimed. must have been the work of an amateur, said diamond's attorney-- an amateur like michelle. coy brewer: michelle theer had asked for the gun several days before the murder. she had told him that her husband had been abusive, that she was afraid of him. so he gets a gun. he gives her the gun. now, he didn't think she was going to kill him with the gun.

did she just use him, knowing that he was somebody she could use to serve her purposes? she set this up to kill her husband, because she wanted the insurance money and for sergeant diamond to take the fall. michelle theer was a brilliant, cunning, ruthless woman who wanted her husband dead. keith morrison: the military jury, however, didn't see it quite that way. melissa stoddard diaz: the verdict was swift-- guilty as charged. and from that moment on, his demeanor changed. i mean, it was like somebody just sucked the air out of him. the john diamond full of bravado and ego just shriveled away. keith morrison: diamond was sentenced to life in prison without parole. at the time, his family was furious, convinced he was framed. debbie dvorak: you don't expect to be convicted on theory and myth and what-ifs.

show me blood. show me a gun. show me the timeline that works. show me those facts. i'll believe till the day i die that she killed her husband, that she'd planned to have my brother go down for it, so she could live this happy, wonderful life. keith morrison: curious thing, that. as john diamond settled into a life in prison, people around fayetteville could see to their great disapproval that michelle went on with a life uninterrupted. and then, quite suddenly, they didn't see her at all. because michelle theer disappeared. craig melvin: coming up-- michelle wasn't just a missing woman. she was also now a wanted woman. melissa stoddard diaz: there's some speculation that she was tipped off that she had been indicted. because she seemed to really sort of fall off the face of the earth. craig melvin: when "dateline" continues.

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and advanced security. all from the company with 99.9% network reliability. get the 5-year price lock guarantee, now back for a limited time. powering five years of savings. powering possibilities™. comcast business. welcome back to "dateline." shortly after john diamond was convicted in the murder of her husband, michelle theer did something unexpected. she left fayetteville, north carolina, without a trace. authorities weren't done with her yet. but would they be able to track her down? here with the conclusion of "deadly ambush" is keith morrison. keith morrison: leavenworth federal prison--

doing time doesn't come much harder than it does here. this is where john diamond was serving a life sentence for murdering air force captain marty theer. but his former lover, michelle, seemed to have dropped right out of sight. where was she? people weren't seeing her around fayetteville. the da, meanwhile, was convinced she must have conspired with john diamond to kill her husband. she was the brains. he was the brawn-- or in this case, the shooter. though it was all circumstantial, said greg butler, it was persuasive. there was a significant amount of evidence, and i don't think there was any question as to who was involved-- diamond and her together. keith morrison: the evidence-- the life insurance, the affair, the access to a murder weapon, those emails, the coverup. taken together, it was enough to convince a grand jury. and finally, in may of 2002, nearly eight months since her husband was killed, michelle theer

was indicted for first-degree murder and conspiracy. but arrested? no. why? melissa stoddard diaz: there's some speculation that she was tipped off that she had been indicted, because she seemed to really sort of fall off the face of the earth right before that came down. keith morrison: michelle theer vanished. no one, not even her family, knew where she was. lauderdale by the sea is a charming little town just north of miami, quaint and quiet, low-profile. in the summer of 2001, cindy geezy, a local landlord, met with a woman who wanted to rent a room at her cottage. cindy geezy: she gave her name as liza pendragon. i let her sign a six-month lease. she seemed well-spoken, intelligent. she told me that she was on the run from an abusive boyfriend in california. keith morrison: she made friends around the neighborhood. before long, she had a new beau. liza-- it was really michelle, of course--

kept in touch with her family very carefully, secretly. she only called on payphones, for example, and that, rarely. two months after michelle arrived in florida, she asked her boyfriend to call her parents, pass on a message. use a payphone, she told him. and maybe he forgot, or perhaps she didn't tell him why, but he called from his parents' house phone. us marshals were monitoring. they looked up the number that had called michelle's parents. and the database told them that this woman had a son in his mid-20s who lived in the south of florida. keith morrison: did he know the missing michelle? the cops found him, staked him out, then followed him to that little white beach cottage, where he and michelle were in for a big surprise. following a developing story out of florida, a woman wanted for the murder of her husband, a pope

airman, has been arrested in florida. at the time of her arrest inside the apartment, we found magazines describing ways to go undercover in the united states, obtain new identity. keith morrison: books, too, on learning spanish, travel guides for several latin countries, an array of fake ids. and then, there was michelle's appearance. vince pastillo: she had changed her appearance, cut and dyed her hair, had some plastic surgery done. reporter: do you have anything at all to say? reporter: make any comments? keith morrison: a few days later, michelle, her face still red and swollen and smeared with ointment from cosmetic surgery, was driven back to fayetteville. she was charged with first-degree murder and locked up without bail. and two years later, in september 2004, after turning down a plea deal that would have imprisoned her for 10 years, the prosecutor laid out his case against michelle theer. the proof-- for one thing, all those intimate emails,

which showed, said the prosecutor, how michelle manipulated diamond into a fatal frenzy and made him her fall guy. greg butler: she got john down to the point that he was so upset, that if he couldn't have her, he was willing to kill himself. if you're willing to kill yourself, it would not take much for you now to redirect that and kill someone else. michelle directed him, who got to the point where he was willing to kill marty. keith morrison: that point arrived, said the prosecutor, after that office christmas party when michelle called diamond to tell him that she and marty were heading to the kill zone-- the parking lot of her office building. but she needed him there alone. so after they dropped two coworkers at the lot, said the prosecutor, michelle made a crucial move that inextricably linked her to the murder. remember, the theers began driving home, stopped for gas. but then, michelle, by her own admission, had marty return to the office, supposedly to pick up some work she needed. and well, she dawdled in the office. marty became impatient, went up

those stairs to check on her, and thus walked into an ambush. greg butler: when they left, there would have been no way for that shooter to have any reason to believe that they were coming back, unless he had known, to prior conversation, from michelle theer, she was going to bring him back to that location, go up and do her business, leaving him outside the door, so that he could then murder her husband. that was really your smoking gun? that was the smoking gun that tied her to it. keith morrison: michelle did not testify, nor did john diamond. her attorney belittled the state's evidence as thin and circumstantial. among those speaking for michelle-- psychologist dr. debbie layton-tholl. she was hired by the defense to interview michelle about her relationships to testify as an expert witness. those were the recorded conversations, excerpts of which you heard earlier. the doctor told the jury, michelle wasn't manipulating diamond by stopping and starting their illicit romance. no, it was something else.

debbie layton-tholl: when somebody in a long-term affair, there does tend to be a pattern of pulling away, and then coming back together-- an inability to be decisive. that's not unusual with affairs. keith morrison: besides, claimed the defense, being involved with another man didn't mean michelle was also involved in murder. the two sides battled through three months of trial time, from labor day past thanksgiving-- 11-week trial, three-hour deliberation. the verdict-- guilty. paul woolverton: she stood up. you know, they put the handcuffs on her, and she walked out of the courtroom, and she never looked back into the courtroom area, not even toward her family. keith morrison: michelle theer was sent to a north carolina prison, halfway across the country from her co-conspirator, john diamond. now, these former lovers shared only one thing-- life without parole.

his supporters are heartfelt in their certainty that she was the bad one. she did it all, and he didn't do anything. and her supporters all blame him and say that he did it without her knowledge, because he was in love with her, and she was breaking up with him. keith morrison: michelle theer rolled the dice. she turned down a deal which would have released her before long. instead, the woman who followed her dissatisfaction to an internet romance went on trial, and as a result, will die in prison. craig melvin: that's all for this edition of "dateline." i'm craig melvin. thank you for watching. happy holidays. i hope you're having a wonderful holiday season tonight and we have a special edition called the egot edition at