yes. >> a cold-blooded killing, but who pulled the trigger? did jealousy drive someone to murder or did she? >> michelle theer was a brilliant, cunning, ruthless woman. ♪♪ hello. 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 a cross fire of a lover's triangle. here is 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? >> i need an ambulance. >> where are you at? >> i don't know. >> okay. what's your name. >> michelle. >> 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 startsing a new career as a psychologist, often counseling troubled couples. >> she was relatively new with her license. i think that was her first real job. >> 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 have spoken to, wanted to be somebody and really worked hard to get to where she ultimately got her degree and became a professional. >> 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. ♪♪ >> she was 20 when she married him at the academy's famous chapel alternate side of the street side colorado springs. >> marty, you may kiss your bride. >> 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. >> we did everything together. he treated me really well. i thought we had the perfect relationship. we were best friends. >> 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 outposts in oklahoma and alabama and florida, and then 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 of that time alone, not so 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 really difficult for her. she was lonely. >> 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 would be stuck raising them by herself in a town where she was already miserable and lonely. >> here i was in fayetteville, loserville, and i had nobody to hang out with, nobody i could pick up the phone and call. >> that actually is about the time it started. harmless really, just a few key strokes, 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. >> john loved women. john was a ladies' man. john always had girlfriends. >> so debbie dvorak, john ease kid sister, could certainly see her brother responding to a solicitation like michelle's. >> my brother has a great personality. he's an attractive guy and, you know, his personality makes him that much more attractive. >> then a few days after meeting online, they met in person at a local restaurant. >> he was charming. he was funny. talked about movies and musing and things that me and marty didn't talk about. >> john diamond was an army staff sergeant, based at ft. bragg, trained as a sniper, highly regarded and 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 his first wife and married and they had a son together. >> michelle didn't know that john was still married, but maybe it didn't matter, at least not then. she loved the sks ex, the attention, the excitement. >> i mean 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's what he was smitten with, having sex with her. >> for michelle, it was more lust than love. >> she felt that the affair didn't take away from the fact she loved marty. she said he was the love of her life and she never loved john diamond. >> and marty? he was in the dark, of course. when michelle told him their marriage was in crisis and they needed to see a counsellor -- >> he wouldn't agree with counseling and i moved out. he was shocked. >> michelle got her own place and spent much of that steamy fayetteville summer with john diamond. >> he was so attentive. he would rub my feet for five hours if i wanted him to. >> diamond was apparently nuts about michelle, never met anyone like her before. >> she challenged him in ways he had never been challenged before. >> paul woolverton is reporter with "the fayetteville observer." >> she was strong and intelligent and exciting for him. >> 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. >> 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 travelled 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 tell the psychologist, insisted it was just a relapse. >> i knew that i loved marty. and i knew that i wanted to make it work in my heart. >> but john diamond was devastated or so said michelle. >> 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 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. >> we had the whole talk, we are going to be friends and it can never happen again, never, never, never. he seemed very calm, very rational. >> 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. coming up -- >> it wasn't like bang, bang, bang. it was bang, pause, bang, pause. >> which sounds more like what, an execution? >> you could take it that way, yes. >> when "dateline" continues. rio knows a moment this pure... ...demands a lotion this pure. new gold bond pure moisture lotion. 24-hour hydration. no parabens, dyes, or fragrances. gold bond. champion your skin. we're carvana, the company who invented car vending machines and buying a car 100% online. now we've created a brand-new way for you to sell your car. whether it's a year old or a few years old. we wanna buy your car. so go to carvana and enter your license plate answer a few questions. and our techno wizardry calculates your car's value and gives you a real offer in seconds. when you're ready, we'll come to you, pay you on the spot and pick up your car, that's it. so ditch the old way of selling your car, and say hello to the new way at carvana. ♪i want to break free♪ (vo) ready to break free? let's get away to a place where we can finally be free. ♪i've got to break free♪ (vo) plan your getaway with norwegian. sail safe, feel free. ♪♪ 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, and has seen about everything. it is an old town, fayetteville. that tower marks the spot where north carolina ratified the federal constitution in 1789. i'm standing on what was a slave market. sherman fought battles here in the civil war. now it is a military town and 160,000 acres back there is the army's fort bragg where soldiers prepare to go to war, and nestled up beside that is pope air force base. two institutions, two professional military men, and one woman. that woman found herself caught between two, marty, her air force captain, and her former lover, army staff sergeant john diamond who just wouldn't go away. >> 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. >> 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. >> they had gone to this christmas party that she specifically asked her boss if marty could go. >> 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 p.m. marty, michelle and the co-workers prepared to leave the restaurant and 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 had forgotten something at the office. >> we ended up turning around and going back to the office to get some stuff that i needed so that i could stay home and work that night. >> 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 911. >> i need an ambulance, please. my husband -- >> somebody shot your husband? >> i think so. >> somebody shot your husband? >> i think so. >> where are you at? where are you at? okay. what is your name. >> michelle. >> 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 castillo. >> she said she heard what sounded to her like three bangs of a car backfiring. >> and 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. >> 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. >> detectives combed the parking lot surrounding the 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. 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. >> 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. it 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. >> 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 a street just looking to find someone. it made it very suspicious. >> 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 have heard so far is the real story. and as you will see, the question of what was true and what wasn't could be very tricky indeed. michelle said she had gone back to her office because she had forgotten something. so what took so long? coming up -- >> 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. >> for what? when "dateline" continues. early audiences give "sing 2" an a+. i counted nine smiles, two belly laughs and five chuckles. it's a heartwarming crowd-pleaser. woo! -i love you! i don't suppose any of you could tap dance, huh? ♪ come on, dance with me ♪ it's the holiday event you won't wanna miss. ♪ come on, dance with me ♪ ♪ i'm levitating ♪ ♪ i'm levitating ♪ [ groans ] i think she's trying to kill me. ♪♪ it was a week before christmas 2000, and fayetteville was aglow, but not everywhere with the lights of christmas. 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. >> somebody went to kill marty theer that night. there was no evidence of any robbery. there was no evidence of any other thing going on here. >> though inside michelle's office what they found seemed, well, a little odd maybe. >> that she had 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 to find a book wouldn't take very long. >> 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. >> 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 cellphone records and discovered -- >> they had been calling each other regularly, a minimum of 20 times a day. >> 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 al buy. he was home with his family watching a movie. still, michelle must have harbored some sort of suspicion about john diamond, who is now a person of interest. not long after the murder, she told detectives and that psychologist she went to see diamond, conduct her own investigation, find out what he knew about marty's death. >> i said, do you know anything about this. do you know anybody that had anything to do with this? he said, no, i would never do anything to hurt you, i know how much you love him. he looked so trustful. >> mind you, as police were soon aware, michelle had many opportunities to question her friend john after her husband died. >> there were witnesses saying that he parked down a little side street and then walked through their yards, going in the back door of her house. >> he couldn't stay away from her? >> yeah, he was going there and staying all night. >> 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. >> 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. >> i knew that i was depressed and i was getting more and more depressed, and i think i went to john for comfort. >> 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. >> he acted as if nothing was wrong because he knows he didn't have anything to do with it, he didn't shoot him. >> 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. 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. >> which just happened to be a .9 millimeter berhe etta beretta pistol, the same kind of gun that killed marty theer. >> john diamond actually borrowed the gun from him during the time frame the murder occurred. he had possession of it. >> detectives were not only convinced that he 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. >> 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's side. but if you'll 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. >> 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? coming up, a secret about john and michelle's steamy affair becomes very public. >> she was taking him to these sex clubs and saying, it's okay, go, you know, if you want to have sex with her, that's fine. and he just, wow, okay. when "dateline" continues. age before beauty? why not both? visibly diminish wrinkled skin in... crepe corrector lotion... only from gold bond. i'm dara brown. here is what is happening. nearly 2,500 flights were cancelled on christmas day. thousands of travelers were left stranded at airports. almost 200,000 new covid cases were reported in the u.s. on christmas eve. a tsa security officer at newark international leapt over a conveyor belt to save a 2-month-old child who stopped breathing. the officer performed the infant version of the heimlich maneuver and was able to get the boy breathing again. now back to "dateline." ♪♪ welcome back to "dateline." i'm craig melvin. all staff target john diamond was arrested for admitting that he had brought an unrej stormrangered gun on to a military base, the same type of weapon used in the fatal shooting of his lover's husband. he was not investigators' prime suspect but they needed more evidence. continuing with our steph, here is keith morrison. >> a few weeks after the murder of captain marty theer, a fayetteville police detective named c.t. 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. >> i just was looking for documents or text messages or e-mails. >> like an onion he peeled back the layers of text, which though they had 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. >> 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 spinner type clubs. >> that would be carolina friends, a swinger's club. it boasted more than 10,000 members. within michelle's lengthy list of e-mails detectives discovered that not-so-innocent inquiry she typed seeking a rendezvous man. that was john diamond who replied and who the e-mail trail revealed quickly joined michelle in the lifestyle. >> she was taking him to these sex clubs and saying, it's okay, go, you know, if you want to have sex with her, that's fine. go, i'm fine with it. and he just, wow, okay. >> but as investigators sorted through the sexually-charged e-mail they could plainly see a story as old as time. john diamond fell head over heels in love with michelle. >> he was her little puppy to be controlled anyway she wanted to control. >> he was like the child in the relationship. >> whatever she wanted, he was at her beck and call. >> hundreds upon hundreds of lurid love-sick e-mails, john diamond appeared to be a man obsessed. i can't wait until 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 know matter how you have hurt me. >> you could tell it changed from a sexual relationship to completely, totally enamored with her anyway you can imagine. >> and he was death pratt to be with her. >> he was willing to do anything, keep the woman he was in love with. >> anything, perhaps even kill the man who stood between him and michelle? >> she was beginning to set him up. shelves playing his emotions. she was pushing him away. >> pushing him away in some ways but without really completely pushing him away. >> push/pull. >> i think she was manipulating him at that point. >> manipulating him into murdering her husband? why would she want to do that. >> there was a $500,000 insurance policy taken out on marty theer in 1999. >> and the sole beneficiary, michelle theer. joon de blasio moond's family were outraged at such a theory. they were convinced michelle typed the e-mails and sent them to herself to steer investigators away from herself and to diamond so he would take the rap. >> he never expressed a love feeling to me. unless you come to me with a handwritten letter he was obsessed with her, i'll never believe that. >> 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. >> according to debbie, it was michelle obsessed with john and never more so when she gave john two wedding rings to take to her brother who was at this point locked in the brig. >> i think she was obsessed to the point she couldn't control him, she couldn't control the situation. >> she wanted to control it. if she gave him a wedding ring and he wore it, wouldn't that give her all kind of reason to claim that he would do anything for her, including kill her husband? >> that could be. i don't -- i don't know. what i got from him after he was arrested was he didn't want anything to do with her. nothing. >> with or without michelle, john was in big trouble so he lawyered up with prominent fayetteville attorney corey 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. >> but military investigators were convinced diamond was the trigger man 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. >> 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. coming up -- the prosecution's case against john and the defense's case against michelle. >> michelle theer was a brilliant, cunning, ruthless woman who wanted her husband dead. when "dateline" continues. >. firefighter maggie gronewald knows how to handle dry weather... ...and dry, cracked skin. new gold bond advanced healing ointment. restore healthy skin, with no sticky feeling. gold bond. champion your skin. ♪i want to break free♪ (vo) ready to break free? with no sticky feeling. let's get away to a place where we can finally be free. ♪i've got to break free♪ (vo) plan your getaway with norwegian. sail safe, feel free. a must in your medicine cabinet! less sick days! cold coming on? zicam is the #1 cold shortening brand! highly recommend it! zifans love zicam's unique zinc formula. it shortens colds! zicam. zinc that cold! ♪ it after a night like this, crest has you covered. crest, the official toothpaste of santa. follow us @crest to celebrate the 12 days of crest smiles. ♪♪ 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. >> 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. >> and nine months after the murder in a small fort bragg courtroom, diamond went on trial before a military jury. >> 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. >> 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. >> 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. >> 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? >> her mother heard him come home, you know, in the wee hours and wash clothes. >> true? maybe not, said defense attorney corey brewer. her story changed after she talked to police. >> she was afraid of the government. i don't think that she was telling the truth. >> had she been pressured? besides, said the defense, there was no dna, no footprints, no fingerprints to prove diamond shot marty theer. anyway, diamond was a trained sharp shooter, 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. >> michelle theer had asked for the gun several days before the murder. she had told him that her husband had been abusive and she was afraid of him. so he gets the gun and he gives her the gun. now, he didn't think she was going to kill him with the gun. >> did she just use him, know 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. >> the military jury, however, didn't see it quite that way. >> 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 shrivelled away. >> diamond was sentenced to life in prison without parole. at the time his family was furious, convinced he was framed. >> 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 will believe until the day i die that she killed her husband, that she planned to have my brother go down for it so she could live this happy, wonderful life. >> curious thing that. as john diamond semgtsed 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 base michelle theer disappeared. coming up -- michelle wasn't just a missing woman. she was also now a wanted woman. >> 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. when "dateline" continues. i was uncertain... was another around the corner? i wanted to help protect myself. my doctor recommended eliquis. eliquis is proven to treat and help prevent another dvt or pe blood clot. almost 98 percent of patients on eliquis didn't experience another. ...and eliquis has significantly less major bleeding than the standard treatment. eliquis is fda-approved and has both. don't stop eliquis unless your doctor tells you to. eliquis can cause serious and in rare cases fatal bleeding. don't take eliquis if you have an artificial heart valve or abnormal bleeding. if you had a spinal 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wouldn't miss the show and mommy always keeps her promises. oh, no! seriously? hmm! it's not the same if she's not here. oh. -what the. oh my goodness! i don't suppose you can sing, can you? ♪ the snow's comin' down ♪ -mommy? ♪ i'm watching it fall ♪ watch the full story at www.xfinity.com/sing2 ♪♪ 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. >> leaven worth federal prison. do intime 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. i don't think there was any question as to who was involved, diamond and her together. >> the evidence? a life insurance, the affair, the access to a murder weapon, those e-mails, the coverup. taken together it was enough to convince a grand jury, and, finally, in may of 2002, nearly 18 months since her husband was killed, michelle theer was indicted for first degree murder and conspiracy. but arrested? no. why? >> 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 out. >> 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 a local landlord met with a woman who wanted to rent a room at her cottage. >> she gave her name as liza pendragon. she seemed well-spoken. she told me she was on the run from an abusive boyfriend from california. >> she made friends around the neighborhood. liza, michelle, of course, kept in touch with her family carefully, secretly. she only called on pay phones, 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 pay phone, she told him. maybe he forgot or perhaps she didn't tell him why, but he called from his parents' house phone. u.s. 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 to lived in south florida. >> 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 in florida we found magazines describing ways to go undercover in the united states, obtain new identity. >> books, too, on learning spanish, travel guides for several latin countries, an array of fake ids. and then there was michelle's appearance. >> she had changed her appearance. cut and dyed her hair, had some plastic surgery done. >> do you have anything at all to say? >> make any comments? >> 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 of 2004, after turning down a plea deal that would have imprisoned her for ten years, the prosecutor laid out his case against michelle theer. the proof, for one thing, all of those intimate e-mails which showed, said the prosecutor, how michelle manipulated diamond into a fatal frenzy and made him her fall guy. >> she got john 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 nor for you to redirect that and kill someone else. michelle directed him. it got to the point where he was willing to kill marty. >> that point arrived, said the prosecutor, after that office christmas party when michelle called diamond to tell him she and matter were headed to the kill zone, the parking lot of her office building, but she needed him there alone. so after they dropped two co-workers 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. then michelle, by her own admission, had marty return to the office, supposedly to pick up some work she needed. while she dawdled in the office, marty became impatient, went up the stairs to check on her, and thus walked into an ambush. >> when they left there would have been no way for that shooter to have a reason to believe they were coming back unless he had known through prior conversation with michelle theer she was going to bring him back to that location, go up to do her business, leaving him outside the door so he could then murder her husband. >> that was really your smoking gun? >> that was the smoking gun that tied her to it. >> michelle did not testify nor did john diamond. her attorney belittled the state's evidence as thin and circumstance. 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 record it conversations, excerpts of which you heard earlier. the doctor told the jury that michelle wasn't manipulating john by stopping and starting their illicit romance. it was something else. >> when somebody is 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. >> 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. >> 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. >> michelle theer now sits in a north carolina prison, halfway across the country from her co-conspirator john diamond. today these former lovers share 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 don't do anything. >> and her supporters all blame him and say he did it without her knowledge because he was in love with her and she was breaking up with him. >> 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 . i'm craig melvin. >> i'm natalie morales. >> and this is "dateline." >> we heard all this talk around the town that jessie was dead. to know that the last moments she spent on this earth she was in so much fear, it's not fair. if he's still out there, he could still be plotting and he could still be hunting. who's next.