>> all the time, the killer was hiding in plain sight. >> no indication she had ever spoken to him? >> no. >> then old detective looked at old lead and person no one suspected of murder was suspect number one. >> perfect murder. almost ♪ hello and welcome to "dateline. she was a new bride, married just three months, then she was found murdered what happened to her remained a mystery for decades, partly because police mistakenly believed she was killed during a break-in gone bad. but when detectives finally reopened this case, they discovered it wasn't a burglar but a suspect whose trail led right to their own front door. here's josh mankiewicz with "the smoking gun. >> february 2nd, 2009, homicide detective arrives before dawn at los angeles police department's van nuys station. >> i was tired >> reporter: had nht before, and beer flowed freely. >> seemed to be good way to spend the day, cup of coffee and caught up on reading. >> reporter: cup of aspirin. >> maybe >> reporter: reached for a file sitting on his desk for months, murder of sheri rasmussen. shot to death in her condo, a few miles from where nuttal worked just as troubling, murdered a generation ago, february 1996. meaning the odds of catching her killer were slim to none >> memories fade, evidence has to be relocated, so it's obviously uphill battle, what you're working with. >> reporter: doesn't begin to describe it. cold case file that he opened that bleary eyed monday morning would lead him on chase of a lifetime and shake the foundations of the lapd. dates back to 1986 and battle for truth by parents of a young bride. >> we miss her every day. >> nils and loretta rasmussen. >> doesn't make a difference what day it is, it's a pain always there, no cure for it >> reporter: who would want to kill sheri rasmussen she was hardworking, popular with friends and coworkers, a nurse at local hospital. >> implementing the program. >> devastating day she was 29 years old, just in the prime of her career. >> reporter: althea kennedy was sheri's boss at the hospital and had originally hired her. >> we couldn't believe it first of all, how could someone do this people crying, people upset. the hospital was like a tomb, you know, so the loss was really p palpable >> reporter: sheri had just been married to engineer john ruttan. >> were they happily married >> unusually so. >> reporter: but months after the wedding, john found sheri sprawled dead on the floor of their home he might seem a likely suspect but john was cleared almost immediately. lapd focused instead that this was a burglary that turned violent. >> this was no accident. >> reporter: retired crime scene investigator and consultant to "dateline." >> multiple shots fired, at close range. >> reporter: she's reviewed court records and media reports on this case we return with her to the actual apartment where sheri was found murdered to try to understand what happened. police think maybe the killer just walked in the open front door. >> they didn't find any forced entry, so yes they're assuming the front door was open and kill killer walked right in >> reporter: and here was a confrontation. >> appears to be a struggle. not just a struggle but shots fired at this point. one shot clearly goes straight through the back slider, and another shot that went through sheri and back out through the slider also. >> so sheri is now wounded and tries to get back downstairs. >> correct she's bleeding profusely, very wounded. gets down these steps appears like trying to go out the door or make it to alarm box where there's a panic button we believe sheri went down in this foyer area due to the fact you could see marks in this as well as broken finger untinailsm her hands. >> reporter: tremendous fight going on. >> killer is dragging her through this area, takes a vase, hits her in the head, knocking her out, grabs blanket, muzzles the gun and does a contact shot into the victim. >> reporter: so that's an execution. >> that would be correct >> reporter: as for a motive, it seemed to be in plain sight, just a few feet from sheri's body >> they found vcr and disc player stacked up by the front door. >> as if going to steal them >> indication this was burglary or home invasion gone wrong. >> reporter: purse was missing and bmw, a gift from john. no sign of the murder weapon but detectives did recover two .38 caliber slugs and something else. >> inside of sheri's right arm they found a bite mark crime scene analyst swabbed it for saliva that could belong to the killer. >> reporter: and contain dna from whoever bit sheri this was 1986, years before dna testing technology would arrive to link a suspect to a sample like this one. back then the dna wasn't much help, but the swab was carefully packaged and bundled with all the other evidence for now detectives didn't have much else to work with no eyewitnesss, no useable fingerprints, no clear motive except the theory of botched burglary. >> by the level of violence that occurred in the residence, theory was it was a man or two men who went in the residence for a home invasion that had gone terribly wrong, murdered the victim to cover up the theft and fled. >> gone wrong because sheri somehow surprised them, panicked and shot her, then fled. seemed to make sense, especially since sheri had no apparent enemies who wanted to kill her or so they thought. >> coming up - >> went to sheri's office, said if she couldn't have john, nobody good. >> when "dateline" continues ♪ all the way out here just for a blurry photo of me. oh, that's a good one. wait, what's that? that's just the low-battery warning. oh, alright. now it's all, "check out my rv," and, "let's go four-wheeling." maybe there's a little part of me that wanted to be seen. well, progressive helps people save when they bundle their home with their outdoor vehicles. so they've got other things to do now, bigfoot. wait, what'd you just call me? bigfoot? ♪ my name is daryl. is skincare from 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has changed, we may be able to help. if yit's very common to havehave has changedsensitivity a gum health concern as well. you know, i talk to dentists every day and they're able to recommend new sensodyne sensitivity & gum. it's really good dentistry to be able to recommend one product that can address two conditions. the year was 1996, crack was hitting los angeles and city of angels was becoming a violent place. murder rate hit killings that year three times the amount of 2016, and lapd was stretched very thin. >> this is time homicide was booming in los angeles. >> reporter: best selling author >> proliferation of high-powered weaponry, gangs expanding and drugs hitting the street detectives were overwhelmed. >> reporter: now the cops have hands full with especially heinous crime in sprawling san fernando valley. sheri rasmussen brutally murdered then a possible lead consultant for nbc news. >> in the same vincinity another woman was approached in her resident by two males at gunpoint also a home invasion robbery situation. thought these two men could have something to do with the murder. >> reporter: a composite sketch was released but still had no prints, witnesses or murder weapons connecting them or anyone else to sheri's murder, and dna was useless. right now. police collected it anyway, why? >> at crime scenes, if there's possible evidence you're not going to leave it behind great forethought to recover it. >> reporter: detectives scoured the condo and complex. only thing apparently stolen from the garage was sheri's car, recovered a mile from the crime scene with the keys still in it. only other thing missing, sheri and her husband's marriage license. seemed an odd thing to steal cash, computers and jewelry weren't touched. wasn't only thing strange. crime was very violent for a two-bit burglary. >> overkill. >> sheri's boss had to review her autopsy for insurance reasons and was struck by what she saw. >> i thought she really put up a heck of a fight. wasn't real surprising sheri was tall, athletic and i'm sure wouldn't go down easily. >> the lapd theory back then was that there were two men robbing the house so sheri would have fought with two guys does that sound like sheri >> that part didn't make a lot of sense to me if there were two men and they had a gun, just seemed weird >> because sheri wouldn't be in a fight with two guys who were armed? >> i wouldn't think so >> a woman >> i think she would have taken on a woman. >> we just really want to know what happened. >> reporter: sheri's parents never thought it was a burglary. had strange encounters dined at restaurant. woman watching her >> scary eyes. >> run-in at hospital where sheri worked >> went to sheri's office and said if she couldn't have john, nobody could >> reporter: most terrifying, encounter in sheri's own home and by now she knew who the mystery woman was. >> she heard a noise and looked up there was john's ex-girlfriend. >> how did she get in the house? >> we have no idea >> reporter: john's e ex-girlfriend appeared to be stalking sheri but never mentioned her name to her parents. wanted them not to worry. >> see if i can't work this out myself. >> reporter: that conversation in a dinner celebrating sheri's 29th birthday. afterwards took sheri to the airport. >> as she walked away, turned and gave me a big smile, and i relived that smile for years >> reporter: less than three weeks later, sheri rasmussen lay dead the rasmussens insist that early in the investigation they told the lead lapd detective about sheri's troubling encounters with john's ex-girlfriend. >> i told the detective not once but probably 15 to 20 times. and he said trouble with you, watching too much tv. coming up, old evidence offers new clues. >> suspect made it appear to look like burglary, staged it to mislead the initial investigation in 1986. she was execute. >> when "dateline" continues jim, could you uh kick the tires? oh yes. can you change the color inside 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>> from what it appears, investigators may have followed the initial theory that it was a burglary. >> reporter: and woman involved in the burglary? >> in hindsight, organization that may have slipped through our hands as organization. >> reporter: but now nutall looked at the photos and developed his own theory sherri rasmussen was shot at point blank range after violent struggle and despite the stereo equipment stacked by front door, very little was actually stolen. >> suspect made it look like burglary, staged it to mess up the investigation in 1986. she was executed. >> reporter: someone had wanted sherri rasmussen dead, so nutall dug through the file for name, female name. >> three we eliminated almost immediately for insufficient motive. >> reporter: but still two name left, one a coworker >> a woman named deb braorah th worked with sherri in the hospital replaced by sherri in official capacity and problems followed after that. >> reporter: bad blood between them >> a motive. >> reporter: deborah had moved and nutall asked local law enforcement to watch her and secretly snag her dna for comparison testing in the meantime learned more about the second husband, contacted john ruetten, now remarried. >> in relationship with stephanie lazarus. >> reporter: that was the other name still on the short list of suspects nutall pressed john ruetten for more on their relationship started as students in ucla, dated on and off until john got engaged to sherri. even then -- you're convinced th lazarus overlapped with the relationship with his wife >> we know from john, at least one incident he was engaged and intimate with stephanie lazarus, it was love triangle and lazarus had deep feelings for john ruetten, maybe a motive to hurt sherri rasmussen >> reporter: scorned lover or coworker a few weeks later cops in northern california tracked down deborah and scooped up a sam of her trash which contained dna. it was sent to the crime lab in l.a. for hours later, came the . >> she was not the donor of the dna from the bite. >> reporter: left just one suspect, john ruetten's ex-girlfriend stephanie lazarus. nutall called the rasmussens. >> there was message from detective, they wanted to talk to us. i thought oh, yeah, right. thought it was another false hope >> reporter: this was detective nutall >> right. >> he said they were opening the investigation. >> upset with me, detective, where have you been the last two decades? >> reporter: now nils rasmussen explained it all, how he told detectives in 1986 someone was stalking his daughter sherri, a woman with crazy eyes, the ex-girlfriend of sherri's husband. nils had never known the name stephanie lazarus but did know something else about her, something very important, and by this time, detective nutall knew it too. >> he was cautious with what he said, but said we would be hearing more from him. >> reporter: nutall had ample reason to be cautious because he'd learned that stephanie lazarus wore the same badge he did. >> we now have a los angeles police officer as a person of interest in a murder case. >> reporter: add you thought i've bitten off more than i can chew >> toto, we're not in kansas anymore, that changed everything. coming up, top secret investigation as detectives go after one of their own >> we would never leave a paper trail of what we were doing. she worked our unit. >> when "dateline" continues wh. get in its way. hpv can affect males and females... and there's no way to predict who will or won't clear the virus. but you can help protect your child by taking a first step. the cdc recommends hpv vaccination at age 11 or 12 to help protect against certain cancers. hey cancer! not... my... child. don't wait... talk to your child's doctor about hpv vaccination today. don't wait... when you drink or eat something that's acidic everyone is at risk for enamel loss. it sucks the minerals out of the tooth's surface. pronamel is formulated to help deliver minerals to the tooth's surface to help reharden and strengthen your enamel. i have moderate to severe pnow, there's skyrizi. ♪ things are getting clearer, yeah i feel free ♪ ♪ to bare my skin ♪ yeah that's all me. ♪ nothing and me go hand in hand ♪ ♪ nothing on my skin ♪ that's my new plan. ♪ nothing is everything. keep your skin clearer with skyrizi. 3 out of 4 people achieved 90% clearer skin at 4 months. of those, nearly 9 out of 10 sustained it through 1 year. and skyrizi is 4 doses a year, after 2 starter doses. ♪ i see nothing in a different way ♪ ♪ and it's my moment so i just gotta say ♪ ♪ nothing is everything skyrizi may increase your risk of infections and lower your ability to fight them. before treatment your doctor should check you for infections and tuberculosis. tell your doctor if you have an infection or symptoms such as fevers, sweats, chills, muscle aches or coughs, or if you plan to or recently received a vaccine. ♪ nothing is everything ask your dermatologist about skyrizi. ♪ i'm dara brown, breaking overnight, son of federal judge has been shot and killed at their home husband has been shot. police where investigating over 3.7 million people have been infected with coronavirus in the united states more than 141,000 have died now back to "dateline. >> welcome back to "dateline." i'm natalie morales. sherri rasmussen had been murdered in los angeles in the 1980s. from the outset her parents told investigators about several run-ins sherri had with her husband's ex now detective was focusing on the same woman, a member of the lapd here's josh mankiewicz with more of "the smoking gun". >> reporter: for two decades the lapd had but one rasmussen's mu, randomly killed by two men in botched burglary now science had rewritten the script and almost too hot to handle prime suspect, lapd detective named stephanie lazarus. but as detective nutall went back through it, no evidence never spoken to? >> no. >> reporter: only one thing, detective had written stephanie lazarus, po. as if her name had come up, not as suspect no notes >> no paper trail. >> reporter: seemed to be above suspicion. stephanie irene lazarus grew up in california, tomboy of sorts, loved sports attended ucla, played basketball in college met and dated john ruetten long before he and sherri got married after graduating in 1982, surprised her family joining lapd, when only a handful of women entered the force. >> i don't think i knew she was applying >> reporter: stephanie's brother stephen. >> i thought it was cool thing >> reporter: quickly rose through the ranks from patrol officer to detective she was popular, friendly and well regarded. her assignments also included project d.a.r.e., a drug prevention program aimed at kids twice named detective of year. later worked at internal affairs investigating other officers accused of crime or corruption and promoted to the art theft unit personal life was good too, got married to another lapd detective. together they adopted a baby daughter life at home and on the job never seemed better. >> she was a happy person, loved what she did for work. loved her husband, their life. >> reporter: but in 2009, this high achieving cop became the focus of a murder investigation. had to be mindful she had many friends on the force her husband worked the same station as nutall did. >> going to work behind closed doors, never leave a paper trail. >> reporter: and gave lazarus a code name, number five and contrary to police procedure decided not to tell lapd headquarters their new suspect was a fellow detective doing that to protect her or your investigation from her? >> dual purpose. integrity of the investigation and if she was not involved, nobody would ever know about it. >> reporter: four cops knowingly skirted department rules to investigate one of their own >> difficult phase of our career she was one of us, worked our unit, side by side with people around us. >> reporter: but nutall and three fellow detectives didn't waver, built a case on the original files and interviewing sherri's family. it was clear that lazarus had the means, motive and opportunity to kill sherri rasmussen. seemed obsessed with john and his new wife was she the person with the scary eyes stalking sherri to nutall, it added up especially consider this, sherri's purse and contents were recovered after the murder, except for one thing >> only thing not recovered was john and sherri's marriage certificate. >> reporter: after three months of intense, secretive investigation, nutall's team needed one more piece of evidence to either clear detective lazarus or incriminate her. >> needed syrup tishs piece of her dna. not cut out for this work. >> reporter: so brought internal affairs into the loop, hoping to close the loop and recover her dna. she was tailed for days as undercover cops waited for her to leave piece of herself behind finally a retail store it happened ordered a soft drink, drank it, dna on the straw which she tossed in the trash. more than enough for testing two dna samples separated by two decades. 48 hours later jim nutall got a call from supervisor >> simple, just said it was match. >> reporter: good feeling, bad both >> surreal, that call, never forget it. >> reporter: but stephanie lazarus was still free and had no clue after 23 years her own department was on her tail for murder detectives wanted to speak to stephanie to elicit a statement or perhaps a confession but without revealing how deeply implicated she was in sherri rasmussen's murder another secret plan was hatched, this time to get stephanie's side of the story, all captured on tape. >> stephanie lazarus is asked by fellow detectives to help in interrogation, only to discover she's the suspect. coming up -- >> so i must have killed her i mean come on >> when "dateline" continues with skin inflammation. apoquel can work on that itch in as little as 4 hours, whether it's a new or chronic problem. and apoquel's treated over 8 million dogs. nice. and...the talking dog thing? 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>> john ruetten? >> how long did you guys date? >> i don't know -- i mean -- is this something -- you said it was something about art. >> reporter: detective lazarus seemed uncomfortable and vague in her answers, especially when detectives asked about sherri rasmussen. >> you know, i may have talked to her you know - >> mentioned hospital maybe? talked to her at hospital? >> yeah, yeah, i may have -- i'm thinking back, bringing up all these old memories >> reporter: detectives turned up the heat. >> did you have a fight with her? >> fought? >> duke it out with her? >> no, i don't think so. >> you'd remember that right, would be pretty -- >> yeah, i would think so. >> most of us can remember without much difficulty the number of fist fights we've had over the course of our lives but while detective lazarus at one point answers know when asked if she remembers attacking sherri or being attacked, at other times can't recall that ever happened. >> doesn't sound familiar. what are they saying that i fought with her and i -- jump i fought with her so i must have killed her come on. >> reporter: after 45 minutes lazarus realized she was the prime suspect in sherri's murder. >> now you're accusing me of this is that what you're saying >> we're trying to figure out what happened, stephanie >> well i was, you know, i'm just saying, you know, do i need to get a lawyer? are you accusing me of something? >> reporter: minutes later came to an end that must have been as familiar as it was uncomfortable for all of them. >> i know you guys have to do your job and i guess i have to contact somebody >> that's fair. >> because i know how this stuff works. >> reporter: then stephanie lazarus was read the same words she herself had read to hundreds of suspects over the years. >> you have the right to remain silent, do you understand? >> yes. >> reporter: and for just a moment can see the handcuffs placed on her by her fellow officers. >> i'm totally in shock. >> reporter: word of lazarus's arrest traveled fast to tucson where detective nuttall was standing by to deliver the news to the rasmussen family. tell me what you said? >> you were right, folks, you folks were right, and i apologize it took us over two decades to give them that closure. >> feel better >> most gratifying moment of my career. >> i was extremely happy i said i feel like i knew it all along. >> reporter: back in l.a., the lazarus family also got the news >> it was numbing. >> reporter: guessing one of the things you thought for felt, they got it wrong, this is a mistake? >> absolutely. >> reporter: error been made. >> going to get cleared up by end of day >> reporter: right didn't happen. >> didn't happen. >> reporter: stephanie lazarus at any time go home after her arrest, bail set at $10 million, much higher than most murder cases. judge cited her a flight risk due to the strength of the evidence against her cold case had finally been cracked and prime suspect worked right beside them. for the rasmussen family it also brought back bitter memories of the investigation. >> i think it was because she was a police officer and they figured they would cover this one up >> reporter: family hired prominent l.a. attorney john taylor who filed lawsuit against detective lazarus and rest of the lapd, claiming that department deliberately ignored clues pointing to fellow officer. >> earlier missteps of lapd weren't missteps, they were intentional conduct, intentional ignoring of evidence and intentional dereliction of duties, beyond just being sloppy and lazy. >> reporter: fact they didn't close the case and didn't listen to the family, those are not evidence of the cover-up. >> wasn't that they didn't close the case, they didn't do anything to create a case. >> reporter: says in 1986 the detectives were protecting stephanie lazarus. >> they actively covered up the identity of the person who committed this crime. >> reporter: the rasmussen's lawsuit alleging coverup was dismissed in 2011. charlie beck was l.a. chief then, spoke with us about the case. >> i can accept someone unable to solve a crime not solving it. i cannot accept someone covering up a crime or individual involved in a crime. i have absolutely no indication that happened here. >> reporter: nothing suggested they looked away from stephanie or road they didn't want to go down >> i think it was lack of ability, not deliberate act to exclude stephanie. >> reporter: in february of 2012, nearly 26 years to the day since sherri rasmussen's murder, stephanie lazarus would have her day in court, chance to clear her name and reputation and show that dna evidence isn't always right and that the los angeles police department had it all wrong. coming up, did the lapd have it wrong >> john's still calling, and stephanie went to tell sherri, look, you guys are getting married, tell him not to call me >> we the jury find the defendant -- >> when "dateline" continues whether it's a year old or a few years old, we want to 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. faced the competition and we broke through. olay's retinol24 complex hydrates better than the $100 retinol cream. visibly smoother brighter skin in just 24 hours. olay retinol24. it's very common to havehave sensitivity a gum health concern as well. you know, i talk to dentists every day and they're able to recommend new sensodyne sensitivity & gum. it's really good dentistry to be able to recommend one product that can address two conditions. 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(vo) you include the best in entertainment and you offer it all starting at $35. because everyone deserves the best. this is unlimited built right. only on verizon. in a highly capable lexus suv. at the golden opportunity sales event. get zero percent financing on all 2020 lexus models. experience amazing at your lexus dealer. welcome back there was a lot at stake at murder trial of lapd detective stephanie lazarus, who stood accused of murdering sherri rasmussen. the prosecution believed the dna evidence was smoking gun but the defense said it was tainted. what would the jury believe? here is josh mankiewicz with the conclusion of "the smoking gun". >> reporter: it took 26 years to get here, a generation of false leads, missed opportunities, a family's frustration, a police department's nightmare february 6th, 2012, the people versus stephanie lazarus finally began in a courtroom in downtown los angeles. prosecution laid out a clear case how stephanie lazarus was deeply in lovewith john ruette and was devastated when he became engaged to sherri, then executed her and covered it up by staging a burglary. >> the opening statement was quite dramatic he came up with a theme which was the case was about a bite, a bullet, a gun barrel and a broken heart and that kind of resonated in the courtroom. >> reporter: the jury saw journals police seized from stephanie's home, detailing how upset she was when she learned john was engaged to someone else stephanie's date book was also introduced, which mentioned locksmithing books which could explain no forced entry to the condo. on the day of the murder, patrol officer happened to be off duty. ammunition used in the shooting was same type used by lapd and same caliber as lazarus's off-duty a .38 revolver she reported stolen two weeks before the murder. really smoking gun was the bite mark dna found at the scene. >> dna was center of the case. this shows she was there without the dna, could not have placed her at the condo. >> reporter: and the statistics were staggering. 1 sext illian chance dna belonged to someone else insisting had been mishandled, improperly stamped and sealed. >> vile was protruding, rather than being inside the envelope and sealed to protect the integrity of the evidence. you can't rely on the scientific results. >> reporter: also said that hair, blood and fingerprints at crime scene did not come from lazarus, as for the weapon, several other guns besides stephani stephanie's could have fired the bullet and as for motive, there was no evidence she was obsessed with john quite the opposite. >> john was still calling. and stephanie went to tell sherri, look, you guys are getting married, i'd tell him not to call me >> reporter: after five weeks, it was up to the jury. loretta and nils rasmussen had waited a lot longer than that. do you feel confident? >> never know what a jury's going to do. >> we the jury in the above entitled action find the defendant stephanie irene lazarus guilty of the murder of sherri rasmussen, and further find the murder of the first degree >> reporter: day the rasmussen family thought would never come finally did as their attorney explained. >> family is overwhelmingly relieved that again, their suspicions and today's verdict reflects and confirmed the identity of the person who killed their daughter and intent with which she did it. it's a tremendous relief >> reporter: for the lazarus family, their wife, daughter, sister and once decorated detective was now a convicted killer. >> we really didn't expect this result with the state of the evidence and way mr. oberlin presented the case it's devastating >> reporter: for the lapd, cold case finally solved, painful side effects. >> i'm thrilled that conclusion has been reached and some form of justice been brought to the family would have much rather this not be a los angeles police detective for sure i've known stephanie a number of years, this is a tragedyon a bunch of levels, not something we are proud of that los angeles police detective was involved here >> reporter: sentenced to 27 years to life in prison. as for the wrongful death civil lawsuit sherri's parents filed against lazarus, they were awarded $10 million. ended the case of the detective finally caught by her own department >> she almost got away with it almost committed the perfect murder who better to do thapolice offi that's all for this edition of "dateline." i'm natalie morales. thanks for watching. nd this is " i'm craig melvin. >> i'm natalie morales. >> and this is "dateline". denita was a light in this dark world that's what she was about. she was just a cup of love i'm like, "who saw this coming?" >> a beautiful young student gunned down. >> things like that just didn't happen there >> why who? who would want to do this? >> i thought i had my man. >> her boyfriend was a police officer. i