>> reporter: and when they're all together, ashlea is there too. . i'm craig melvin. and i'm natalie morales. and this is "dateline." >> it's shocking. you just kind of go into crisis mode. >> i don't think they knew exactly what had happened other than he was covered in blood. she was just broken and lost. >> there is a murderer out there. and it's terrifying. >> reporter: it was supposed to be an anniversary celebration. 32 years together! >> they were in love, even after all those years. they were very happy together. suddenly -- an intimate- moment turned to infinite terror! >> i just hear help! someone's in trouble. i was scared. i was scared.

a husband, found murdered in a closet! a wife, tied up in another. >> they found her on the ground with her hands behind her back. >> she just had bruising on her arms and on her face. >> inconsolable, screaming, crying. who could be behing this? >> it just eats me up inside! >> reporter: their only daughter, desperate for justice for her dad. be careful what you wish for. >> everybody gasped. nobody could believe it. >> this terrifies me because this could happen to anybody! this is dateline.

>> reporter: the scented candles were lit. the jacuzzi jets turned on high. it was a belated anniversary evening, but not some big blow out. sandra and jaime really weren't that kind of couple. >> they were just always so kind to each other. and always very respectful. >> reporter: it was really the start of a life victory lap for the two. they'd raised a daughter, juggled all the usual things that families do, and now retirement for jaime was right around the corner. >> they sat there and they talked about the future, and what they were looking forward to. >> reporter: but the future for these two would last no longer than the flame on that candle. by the next afternoon, there would be blood, lots of it. somehow, someone had turned a

cozy celebration into a monstrous crime scene. >> it was just -- it was horrible. >> what in the world had happened in that house? >> i have no idea. >> reporter: the story of the two begins as high school meet-cute. sandra, the new girl from laredo assigned a seat in her houston classroom just in front of jaime melgar. their daughter lizz doesn't know how many times she heard that story. >> he used to pull on her hair. >> oh, you're kidding. >> in the middle of class. >> "who's this guy behind me, pulling on my hair?" >> yeah. apparently, one time he invited her ice skating. and he told her a bunch of friends were going so it wouldn't really be a date. >> and when she shows up, there it's him and one of his friends. and his friend left shortly after that. >> so a little bit of a scheme going on. >> yeah a little bit. but, you know, it ended well. >> reporter: and that was that. sandra and jaime were a done deal, an inseparable couple. sandra studied nursing, and jaime set aside every dime he

could for his family, juggling a job as a computer programmer while investing in real estate. >> happy family? >> very happy family. >> i was definitely a daddy's girl. growing up. >> reporter: and jaime carried himself with a certain goofy joy, as his niece marissa campos remembers it. >> easy going guy? >> yes, very easy going. easy to talk to. had the worst jokes. >> they were so bad that you would just stop and groan. and they became known as jim jokes. >> reporter: marissa's aunt sandra would roll her eyes, then laugh indulgently at uncle jim. >> i remember her being like, "oh, your uncle. oh." >> reporter: the melgars' life revolved around not just family, but church, too. they'd joined the jehovah's witnesses early in their relationship, but by her early 20s, daughter lizz had left the church. newly independent, she rushed into a marriage. a bad one. >> true that he was involved in heavy drugs? >> yes. >> that was the end of it? >> that was it.

i didn't want to live that kind of life. >> reporter: but her parents' marriage just kept going through sickness and health. in fact, in recent years, jaime was looking younger than ever on a vegetarian diet and exercise regimen. >> he realized he was getting older and he just wanted to make sure he was in the best physical shape. >> your mom. your poor -- >> mom. meanwhile had a constellation of health problems, didn't she? >> yes. >> lupus? chemotherapy involved in that? >> at times, yeah. she also had epilepsy. >> did she have the seizures? did you ever see her -- >> yes. yeah, she did. >> reporter: then december 2012 rolled around. their 32nd wedding anniversary. sandra was ill on the actual day. so they went out together ten days later, on december 22nd. >> she was finally feeling well enough to go and have dinner. >> reporter: the next day, the 23rd, marissa's family would join them to celebrate again over a late lunch. >> on our way there, i remember texting him. >> texting your uncle. >> yes. i didn't get a response. but -- >> was that unusual that he didn't text you back? >> yes.

>> reporter: they got to the house around 4:00pm and knocked on the front door. >> nothing. no answer. >> reporter: marissa's father, jaime's brother herman, checked around the back of the house. no sign of jaime or sandra. >> then we thought, "okay, well maybe well, maybe they -- they left. maybe they went to go get something." and then my dad's like, "no, but his truck is out there." so finally that's when my dad said, "oh, i'm just gonna go inside." >> reporter: herman walked through an open garage door, and entered the house itself through an unlocked interior door. >> then he comes around and to open up the front door. >> reporter: the visitors huddled in the dark entrance hall, expecting a greeting from sandra or jaime. but none came. just as they got ready to leave, they heard something. it sounded like sandra. >> it was mumbling. >> where was her voice coming from, marissa? >> we did not know. my dad -- i just remember he just ran straight into the master bedroom. >> reporter: marissa raced after her father. >> i just hear, saying "help. someone's in trouble." >> are you really scared at this point? >> yes, i was scared. >> reporter: the voice was coming from inside a

walk-in-closet attached to the bathroom. herman moved closer. wedged against the door knob was a dining chair. he tugged it aside, opened the door, and there was sandra -- on the floor, tied by her arms and ankles, but alive. >> he said that she did not look well at all. >> reporter: as marissa's mom cut sandra loose, her dad spoke. >> "where's my brother? where's your uncle?" >> reporter: the answer to that, unspeakable. what had happened to jaime melgar? and to his wife? >> she looked like she had aged ten years overnight. >> just broken and lost. >> the only possible witness to a night of terror. >> reporter: what would she remember? >> there was a car following us.

>> reporter: marissa, rattled to her core, stood in her uncle jaime and aunt sandra's bedroom doorway, waiting for first responders, trying to calculate her family's terrible new math. >> i still didn't know everything that was going on. >> reporter: in the bedroom: open drawers, a tossed wallet. had this been a home invasion? and where was her uncle jaime? then she glanced to her side, and there, about 20 feet away from the bathroom, next to jaime and sandra's bed --

>> i just saw his -- his ankles. >> reporter: and this was what? in a closet area off the -- off the master, huh? >> he was in a closet. >> reporter: so you just saw his feet. >> uh-huh. i w -- didn't even know what had happened to him. i just know he was -- his ankles were tied up. it was horrible. >> reporter: there was jaime -- naked, covered in blood, on the floor, not far from his safe. a red rope encircled his chest, a phone cord looped around his ankles. sandra, now freed of her ties, sprang from her closet captivity. a former nurse, she checked for his pulse and found none. your aunt was distraught. she's crying. >> yes. yes. >> reporter: marissa, what in the world had happened in that house? >> i have no idea. i'm not sure who could have done something like that to him -- to them. >> reporter: first responders weren't exactly sure what they'd been dispatched to either. >> they told us that there's possibly two victims, and that's all we knew when we got there. >> reporter: emt stephanie robertson was the first responder on the scene. she checked on jaime. he was clearly dead, huh? >> yeah, clearly dead. yeah.

>> reporter: you know, gunshot wounds from knife wounds. >> you couldn't really tell, there was so much dry blood. i did notice the gash down his neck. >> reporter: next, emt robertson found her way to sandra, by then collapsed on a chair in the bathroom, a family member by her side. >> she was kind of balled up a little bit. and she was crying hysterically. >> reporter: the emt started to assess sandra, who said her head hurt, but -- >> she said she has no injuries. >> reporter: still, sandra seemed disoriented. what time was it? morning or afternoon? then, between gulping sobs, sandra said she simply could not remember what happened the night before. she'd been unconscious -- maybe had one of her seizures. >> she said after a seizure, that it's not uncommon that she falls asleep for several hours. >> reporter: by now, harris county sheriff's investigators had descended on a crime scene that was once just the melgars' modest home. jaime, they could see, had suffered multiple stab wounds to the torso --

by the looks of it, well over a dozen. the crime scene unit got to work inside collecting evidence -- things like a bloody chair near jaime's body, and a kitchen knife, fished out of the bottom of the jacuzzi. sandra, seemingly in shock from her ordeal, declined to go to the hospital. instead, she went to talk with investigators. >> let's start yesterday. >> reporter: sandra told investigators the last thing she remembered was her anniversary night with jaime. >> went out to eat. >> and what time was that? >> i would say about 8:00. i'm just guessing. i don't know. >> reporter: sandra told them they stopped for mixers at a cvs on the way home. >> what time did you get home on friday? >> probably midnight. >> reporter: she said they intended to share some late night romance, candles and strawberries. >> we made some drinks. we went and got in the jacuzzi. >> in your master bathroom? >> right. >> and then what? >> stayed there for about maybe

two hours talking and drinking. >> reporter: but the intimate jacuzzi was disrupted by their dogs barking outside in the yard. >> he got out and said he was moving the dogs to the office. because when they're too loud we don't want the neighbors to complain. and he just, you know, was taking a while so i got out and was gonna get dressed or change in my closet. >> reporter: maybe that's when she had the seizure. >> that's all i remember until i woke up. >> reporter: as they talked, sandra broke down. [ crying ] >> reporter: who could have done this, she wondered? she recalled for the detectives a scary moment on their way home. >> i think when we left cvs there was a -- a car following us because when we came in our neighborhood, it was still behind us and he was really close. >> reporter: something for the detectives to check out. after sandra was done talking, her cousin diana -- who'd rushed into town to help -- met her at

a friend's house. >> she looked like she had aged ten years overnight. she couldn't stop shaking. and so i -- i didn't wanna ask her too many questions. >> reporter: lizz, remarried now, was an ocean away, living in europe, when she finally got her mother on the phone. what did you hear in her voice? >> she was just broken and lost. she was just devastated. >> reporter: and at that point you've got very fragmented information, huh? >> yeah, all i knew is my dad was killed in a home invasion. and thankfully, my mom was still alive. >> reporter: that's just not any kind of news you should ever hear. >> it's shocking. it really doesn't sink in for a while. you just kind of go into crisis mode. >> reporter: lizz booked the next flight back to texas. >> i just knew i had to get there. >> reporter: had to get back. back to a new reality with a murdered father and a traumatized mother. grieving would have to take a

number, while the daughter held everyone together. nothing made sense. coming up -- >> were you worried about your mother? that whoever this person was might come back? >> absolutely. she was traumatized. >> tips begin to trickle in. who could have done this? >> they're getting information right away about kind of a sketchy neighbor. >> that's right. just gettin' out of jail, who was -- suspicious. >> when "dateline" continues.

>> reporter: two days after the bloody discovery in her childhood home, lizz melgar landed in houston. a daddy's girl shaken even more by the face that was missing. >> i think at that time, it really hit me that, i wasn't gonna see him anymore. he wasn't going to be there to pick me up from the airport. >> reporter: a still very rocky sandra came, with family, to pick up her daughter. >> we both just broke down at the sight of each other. >> she'd been through a terrible ordeal? you don't -- really know the whole story yet. but did you see injuries on her? >> she just had bruising on her arms and on her face. >> did she have a bump on her head? >> she did. she told me her head was hurting. and i could feel it back there. >> reporter: lizz insisted her mom get some rest. so the next day, when detectives came by the house where lizz and sandra were staying, the daughter was the one to field their questions. >> and you flew in, uh, yesterday? >> yes. >> that's right. >> okay. >> reporter: and lizz, thought

it prudent to record the conversation. she updated the detectives on her mother's health. >> she's just in complete shock, and she has retrograde amnesia at the moment. she has a hard time remembering things as it is because of the seizures. >> reporter: lizz had witnessed her mom's seizures before. and now she theorized that's what might have kept her alive during the home invasion. >> i think she, she probably had a seizure and that probably freaked out whoever was there, and maybe they thought they killed her. >> reporter: the detectives asked lizz to keep them updated on her recovery. >> because if she could ever remember a suspect, that's the best thing for me and him. >> no i agree. >> yeah. >> 'cause then we have a description, everything else, right now at this point. >> we have nothing. >> i've been asking. >> i've been asking her. >> reporter: and then the detectives asked lizz if she could pay a visit to her parent's house. >> anything you think's missing, because we need to start searching for the items that are missing. >> i can't imagine you going back to this house, where you've known your parents in happy times, and then it's a crime scene. >> absolutely. it's the one place you're supposed to be safe.

and it's just been, i don't know. it's been tainted. >> reporter: she went through the house, room by room, cataloging what she thought was missing. a tv set, jewelry, cash and medication. last stop, the garage. >> the garage was full of things that could easily be stolen and pawned. >> yeah. >> reporter: there lizz spied something, to her eyes, oddly out of place. her middle school backpack. sticking out of it, an xbox console. could this have been the killer's loot, dropped in a panic as he ran from the scene? lizz called investigators. they returned to the house, snapped even more photos, and collected the backpack as potential evidence. they'd later find, beneath that xbox, some of sandra's jewelry. >> reporter: and lizz realized she had an idea for detectives too. a possible suspect. >> is it true, lizz, that you even suggested they take a look at your ex at that point? >> yes. i tried to give them as much information as i could. >> reporter: yes, the ex-husband

the melgars regarded as a no-account. turns out, during the rocky last days of his marriage to lizz, the melgars suspected he and a buddy lifted some of sandra's medication. the same sort now believed to be missing. the melgars never reported their suspicions to authorities, but now lizz told detectives, talk to the ex. >> reporter: by now, the murder break-in story was all over the news. >> reporter: and neighbors started offering up crimestopper tips. >> check out a guy seen lurking around outside the police tape. >> reporter: amanda orr of reuters, and brian rogers, the houston chronicle's legal affairs reporter covered the melgar murder. >> they're getting information right away about kind of a sketchy neighbor, known to break into houses, steal stuff and pawn it. and he's up the block and maybe at the scene that night. >> that's right. a neighbor who had -- just getting out of jail, who was suspicious. >> reporter: lizz thought to add him to the list of potential suspects.

>> did you have ideas for them? >> i did. >> reporter: she also suggested they talk to one of her parents' tenants, someone who'd had disputes with her dad. and there was a co-worker of jaime's she got a bad vibe from. and again, lizz says she urged detectives to look at her ex. he had a record of drug arrests. if not him, what about people in his circle? months dragged by without word on the investigation. >> you believe someone is out there, has gotten away with killing your father. >> yeah, absolutely. it was hard to sleep at night. i was -- every little noise was -- had me on edge. >> were you worried about your mother? >> oh yeah. >> that whoever this person was might come back for her? >> absolutely, i was constantly worried. >> and how was her health at that time? >> she had started having seizures. and you know she was traumatized. she had post-traumatic stress, she had anxiety, she had depression. she was a mess. >> reporter: lizz clung to the hope that one of those leads she gave detectives would eventually pan out.

but for now anyway it looked as though law enforcement was playing its cards close to the vest. according to prosecutor colleen barnett of the harris county district attorney's office, that was because they'd made some early observations about the crime scene. >> officers have investigated burglaries and robberies for many years before they get in homicide. and they thought that the scene looked kind of suspicious. >> so what was off kilter with this one? >> the fact that it didn't look burglarized. >> the drawers were open, i think, right? >> they were open a little bit, but nothing was tossed. >> reporter: but what about those items lizz noticed were missing from the house? and that backpack of apparent burglar's loot she found in the garage? well, detectives took careful note of many other items, pricey things that had been left untouched. >> cameras, the bicycle. there was some painting equipment. there were things that were easy to take that weren't taken. and then the stuff that was taken and put in the backpack was left in the garage. doesn't make sense. >> reporter: the home, to investigators, showed no sign of forced entry.

that open garage door the only possible way in for an intruder. but law enforcement thought that too seemed as though it could have been staged. no. to investigators this didn't look like a burglary gone bad, but more like a targeted killing. and they theorized their suspect was someone already inside the house. coming up -- >> my memory is so bad. >> reporter: how murky was her memory, really? investigators are about to listen very carefully to sandra's story.

>> reporter: the day before >> reporter: the day before christmas eve, also the first anniversary of jaime melgar's death, was impossibly hard for his family --

>> i mean that's all we really think about. >> should be holiday season but it's that's awful memory coming -- >> yes. >> back, huh? >> yes. yes -- we are anxiously waiting for that day to come. i mean doesn't matter if it's tomorrow or if it's ten years from now, but we -- we -- would like some answers. >> reporter: but law enforcement wasn't exactly forthcoming with the melgar family. might have been a reason, they doubted jaime's murderer was a burglar, or even someone else in sandra and jaime's remote orbit. >> there's always a first suspicion of family members, if there's nothing that really makes sense. >> reporter: and that suspicion had narrowed down to the person inside the house with jaime, sandra. her account of a blacked-out 14 hours after their anniversary celebration. >> i wish i could recall. >> reporter: to investigators, was just too weird to be believed. >> my memory is so bad. >> reporter: it seemed implausible to them that sandra really heard nothing the entire

night. >> this is happening in a very small space? the husband is stabbed to death and found in one closet. and she's been tied up in another? >> that's right. >> reporter: the investigators closely studied that interview they'd conducted with sandra. they found her more indifferent than distraught. >> do you know what has happened today? >> my husband was murdered. >> how? >> i don't know. >> reporter: and when sandra broke down crying, the detectives couldn't recall seeing any tears -- detectives believed sandra's story morphed over time -- for instance the part about how long she'd waited to get out of the tub after jaime left to fetch the dogs -- at first she was vague -- >> and he just, you know, was taking a while so i got out. >> reporter: then more specific. >> about 15 minutes, 20 minutes. >> reporter: later another revision -- >> maybe about five minutes. >> reporter: and, detectives were perplexed by what sandra

claimed she did and did not hear that night -- >> hear anybody scream? >> no. >> hear the dogs? oh, you hear the dogs barking? >> yeah because they were outside our window. >> reporter: but, after almost two hours in, as investigators pushed her, sandra seemed to tweak this key element of her story -- >> actually i don't even remember hearing the dogs. my husband's the one that says he's got better hearing than i -- >> reporter: of course, the change-ups in sandra's story could be attributed to shock. but, as the detectives viewed it, sandra was being deliberately evasive. enhancing her story to align with a conjured-up crime scene. >> it sounds like a bloody event. was it? >> it was bloody in the area that he was in. there was blood in the carpet. there was blood on a chair. he, himself, was very bloody. and the closet but nowhere else in the house was there any blood. >> reporter: to investigators' way of thinking, home invaders would have dragged at least a trace of blood on their way out of the house. but crime scene techs did not find any. when the rest of the forensics

came back, the findings had limitations. >> although you have the murder weapon, it's been washed in water for several hours. >> kitchen knife or something? >> a kitchen knife. a large kitchen knife. it was found in the bathtub. and so any dna that had -- could've been on it from the murderer was gone. it was washed away. >> reporter: what's more, no blood was detected on sandra. in fact, no dna or fingerprints linked sandra to jaime's body -- or jaime to sandra's. and while detectives had a hunch about sandra, the evidence didn't seem quite there yet for an indictment. as more time went by, it became clear to members of sandra's family, like her cousin diana, that law enforcement was eyeing her -- >> or so ok. it's okay for you to think that, investigate her, and then you'll see that there's nothing there and move on. >> reporter: but as the investigation dragged into july of 2014, their worst fears were realized, lizz and her mom found out in a most unusual way.

>> i went to the mailbox and it had been absolutely filled with fliers from lawyers trying to get our business for our pending case. >> did you know what that was about? >> i had no idea what that was about. >> and so i got onto the harris county website and i entered my mom's name. and i saw that she had been charged with my father's murder. >> reporter: a few days earlier, a grand jury had quietly voted to indict her. she turned herself in and posted bond. and then she hired veteran criminal defense attorney mac secrest to defend her. >> quite frankly, i can smell bs from across the room. and when i sat down and spoke with her, her story was plausible, i didn't hear anything that -- rang -- kind of a false note. >> reporter: allison secrest -- mac's niece -- served as co-counsel. >> she's a sweet person, she doesn't have a temper. and it was really apparent to us she had a good relationship with her husband. >> reporter: they couldn't

fathom how sandra was under suspicion for a crime that defied physical possibilities. after all she was found tied up, barricaded in her closet -- >> she believes she's had a seizure. or maybe she was actually hit in the head and was knocked unconscious. >> reporter: to these attorneys, the case seemed suspiciously thin -- >> "where's the beef? where's the crime?" i guess more importantly, "where's the investigation?" >> reporter: it had taken more than a year and a half to indict sandra. so what were the detectives doing all that time? well that's an involved story, investigated by nbc affiliate kprc-tv. the lead detective on the case, ruben shawn carrizal, seen here interviewing sandra, had become the center of a scandal. a controversy is growing tonight over a document falsified by a harris county detective now working for the district attorney's office. detective carrizal got himself into serious trouble for falsifying a search warrant in a case not connected to sandra's. and that cast a shadow on his other investigations.

>> that became a probably a really big issue for the prosecution and somethin' that the defense, would be able to -- to definitely use against him -- >> reporter: after the story broke, the detective left the sheriff's department. would it end the case against sandra too? >> did your lawyers tell you, "this thing may never go to trial here. this thing has got so many holes in it?" >> that's what we believed. absolutely. >> reporter: by the summer of 2017, it had been three years since sandra's arrest. she had a right to a speedy trial. it was put up or shut up time for the da's office. >> when you read all your stuff and stepped back and you said, "what do i have here," what was the biggest problem?" >> the biggest problem was that i didn't have that many affirmative acts from her stand point. i had -- >> what do you mean there? >> i couldn't put the knife in her hand. i didn't have any eye-witnesses that she killed him. she didn't confess. >> what did you have going for you? what was the best thing you had going, colleen? >> her story was ridiculous. >> reporter: so the prosecution made the call, the people v.

sandra melgar would proceed to trial. >> reporter: coming up, a deadly seduction? amanda-the prosecution thinks that sandra melgar lured jaime to the bedroom under the guise of sex play pros -- she's massaging his neck, and then she makes a strike straight up. but where was the proof?! >> this case outta scare the hell out of all of you when dateline continues.

>> reporter: august 2017. more than four-and-a-half years after jaime melgar was murdered in, what seemed at the time, a brutal home invasion. but now, sandra, his wife of 32-years, was on trial for jaime's murder. she'd pleaded not guilty. it put daughter lizz in a painful, judicial paradox. >> the people versus are bringing you, the family, victim, justice in their mind. and yet, justice is putting your mother away. >> correct. i've lost my father and here i am, about to lose my mother. this is supposed to be s -- the justice system that -- it's just completely broken. >> reporter: prosecutor colleen barnett's message for the jury was simple, sandra -- and only sandra -- could have done this. >> there's zero evidence. no evidence that anybody else did this. >> reporter: the prosecutor set out to dismantle the theory that

jaime's death resulted from a botched robbery. first responder, emt stephanie robertson, told the jury -- that to her -- the crime scene just looked off. >> it was a little -- disarrayed. the drawers were pulled out nothing was -- appeared to be missing. >> reporter: and the prosecutor used sandra's own words against her. the jury heard that interview with the defendant -- the one where detectives found her so oddly indifferent. >> do you know what has happened today? >> my husband was murdered. >> reporter: and sometimes her story to the detectives didn't gybe with what detectives believed to be the facts. >> she's just trying to tell a tale so that she can go on with her life without being in prison. >> reporter: for instance, her account of jaime getting out of the jacuzzi to quiet the barking dogs -- >> there was a next-door neighbor to the melgars who constantly complained about the barking dogs. she said that night, she didn't hear the dogs barking. like, she slept wonderful. >> reporter: of course, one of the main problems for sandra was

the big picture, so you want us to believe, the prosecutor argued, that home invaders were slashing your husband to death just feet away from you and you remember nothing? really? >> nobody running? nobody saying anything? shouting? >> no. nothing. >> reporter: sandra's explanation was that she'd suffered from seizures and memory loss for years. reporter amanda orr was in the courtroom as the prosecution introduced some of sandra's medical history refuting that. >> she did go to her doctor's appointments, but reported that she was not having seizures. that her medication was controlling them pretty well. >> reporter: so if sandra was, in fact, lying about being unconscious for hours, then she had plenty of time to pull herself together and make the house appear ransacked. >> she had a lifetime to get rid of the clothes, to wash herself up, to get ready for the -- the big finale. >> reporter: though not required to prove a motive, the prosecutor offered one up for the jury anyway.

there was no evidence of infidelity or typical marriage troubles -- still she suggested that sandra wanted out. but their religion made it impossible to split up the usual way -- >> jehovah's witnesses don't allow you to divorce. unless someone's cheating, and it's very clear that jaime was not that guy. >> if i get divorced, i get ostracized and i can't talk with my friends. but if i kill him, and nobody finds out, i'm not ostracized. >> reporter: but wasn't sandra too frail to commit such a violent, close- quarters, crime? maybe not. the medical examiner's report concluded jaime suffered 31 sharp force wounds -- but none very deep. >> so kind of stab, stab, taunting kind of injuries or how -- >> i don't -- >> how do you read it? >> or maybe not much force used. or maybe a weaker person. >> reporter: so how did the attack go down? the prosecutor had a vivid scenario of a lethal seduction. >> the prosecution thinks that sandra melgar -- lured jaime to the bedroom under the guise of sex play.

>> so she gets jaime to sit down in the chair, and maybe she's massaging his neck, and then she pulls it out, and while he isn't looking, she makes a strike straight up all the way to his neck. >> reporter: it was a dramatic show and tell for sure. then, it was showtime for the defense -- the prosecution's case was all invented nonsense, they said. theory strong, evidence light. >> this case oughta scare the hell outta all of you. >> reporter: attorney mac secrest told the jury that sandra was the victim of bumbling, myopic investigation. >> now we've got jaime butchered, this lady falsely accused. >> reporter: and, the defense said, sandra was so clearly attacked herself, barricaded -- and bound. >> or so she's been tied up. she's been left in a closet for 14, 16, 17 hours. >> reporter: they showed these photos in court, and told the jury sandra went to a doctor who confirmed her injuries.

>> when sandy went to the doctor a couple of days later -- she had a full examination. and of course -- hematoma was found on her head. >> reporter: as for that interview. the defense said the only thing it revealed was that the blinkered detectives thought sandra was guilty from the get-go. >> would you want us to find the killer? >> of course. >> i don't think you do. >> reporter: and, they said it showed, in the most trying of circumstances, sandra remaining consistent and composed. >> i had a seizure and so i usually can't move anyway. >> reporter: another point -- a forensic one -- the defense told the jury about dna evidence that had been collected but not presented by the prosecution. >> there's unknown male dna on various drawer pulls from the master bedroom, and door handles, and also on that backpack. so it's huge because it points to a possible other suspect --

>> reporter: and the csis had photographed a bloody swipe on the handle of the closet safe -- just a short distance from jaime's body. the defense told the jury how detectives never ran it for a possible print, nor had it swabbed for dna. >> isn't that the kind of evidence you'd wanna have available to consider? why wouldn't you at least test it? >> reporter: the defense ticked off more examples of what they regarded as inept detective work, they never brought lizz's ex-husband in for questioning. or that neighbor with a history of petty burglaries, the one fresh out of jail. >> the police go to his house, knock. he doesn't answer and they leave their card. >> "call us if you get the time"? >> right. and, and, they never followed up on it. >> reporter: and, the defense thought they knew just how the investigation got so bungled. look at the man who led it. >> what kind of murder investigation would you have where you knowingly, intentionally, and willfully don't bring the lead investigator to court? >> reporter: the defense, not the prosecution, called the

one-time lead detective. they weren't allowed to tell the jury about the scandal involving that other case, but they asked him to account for a litany of perceived fumbles in this, investigation. case in point, a pair of sandra's socks found, not in the evidence room, but, instead, in a filing cabinet, long after he'd left the job. >> it's a really horrible investigation. it's just inept. >> there's no physical evidence in this case that points to her at all. >> reporter: but there was another key element to this prosecution's case. she knew the jury had one big question, was sandra a houdini level escape artist? >> reporter: coming up -- >> so how do you tie yourself up with that? >> all you do is just put it on your tie, a wickedly clever bag of tricks? >> really pull something like this off? >> the jurors would have a stunner of an answer.

>> reporter: sandra melgar's defense attorneys had tried to portray the murder investigation as seriously flawed. but perhaps their most persuasive argument was sandra herself. she didn't testify, but "houston chronicle" reporter brian rogers said her muted appearance spoke volumes. >> you know there's an old adage in defense law. if you make your client look like a schoolmarm, do it. and she sorta comes across that way, as somebody -- >> reporter: kind of frail? >> small. and -- >> reporter: depending on a cane? >> yeah. you know, and you have a hard time believing she could even yell, you know, much less stab anyone. >> reporter: and how could that same petite woman have managed, as the prosecution contended, to wedge a chair beneath the doorknob of the closet that she was already inside and beyond that, bind her own hands and feet. the prosecution had an answer for those houdini-like skills. >> she definitely prepared for this. i'm sure she practiced the chair

behind the -- the door. >> reporter: the prosecutor said sandra had come up with an ingenious way to wedge that chair under the doorknob from the inside. by sliding a pillow sham along the floor. how's that, you ask? well, she played the jury this video of investigators re-creating the process. >> the detectives videotaped themselves putting the chair on the pillow sham and pulling the pillow sham underneath the door so you can pull it closed from the inside. >> reporter: you have to be inside the closet, of course, right? >> that's right. >> reporter: prosecutor barnett said it wouldn't be all that hard for sandra to tie her own hands behind her back. she showed us what she showed the jury. >> reporter: so how do you tie yourself up with that figure eight now? >> it's pretty simple. all you do is just put it on your tie, turn it in the back and you just mess around with it any kind of way. the point is that it looks legitimate. not that it is legitimate. but it looks legitimate. >> reporter: the prosecutor argued sandra did this just minutes before the family discovered her, which explained

what the emt said she did not see on sandra's wrists. >> she had no bruises, um, no ligature marks, nothing. >> reporter: but the very thought that sandra could have come up with these elaborate tricks and executed them. that's sheer speculation, said the defense. >> that's a theory, folks. there's no evidence of that. >> reporter: a theory that the defense said investigators didn't even try to corroborate with the eyewitnesses who'd found sandra. daughter lizz said after that night, investigators never came back to ask the family what they saw. >> reporter: never really spoke to your family again, is that right? >> yeah they never reached out to anybody. they could have asked them about you know the theory of the chair and the mat under the chair. you know, they could've asked them about the surroundings. >> reporter: and they would have heard how the family said they needed scissors to cut sandra free. her wrists so tightly bound. >> i have a big problem with them not following through and talkin' to witnesses who had personal knowledge. >> reporter: the prosecution

said investigators followed the evidence and did a thorough job. it was now up to a harris county jury to decide sandra's fate. the first day of deliberations ended with no decision. >> reporter: when the jury's out, do you go back to your office and pretend to work or what? >> you can't work. no, you try and do other stuff, but you really can't. >> reporter: finally, on day two there was a verdict. >> we were all, "everything's gonna be fine. this is a joke. no worries." >> reporter: surely the jury will see it the way we the family see it. >> exactly. >> reporter: sandra melgar stood to learn her fate. >> we the jury find the defendant sandra jean melgar guilty of murder as charged in the indictment. >> reporter: sandra collapsed into her chair, sobbing. lizz, beyond devastated, grasped for her mother as she was led away. >> it sucked the life out of me. i just felt the room spin. and i just felt like my world was collapsing.

>> we just could not believe it, could not believe that this was happening to her. >> reporter: to prosecutor barnett, this was justice. both for the state and for jaime melgar. >> she's committed a crime. and they found her guilty and i'm glad. i've done my job. and justice has been served. >> reporter: the jury sentenced sandra to 27-years in prison. her lawyers have begun the years-long appellate process. from behind bars, sandra wrote us this letter saying she's at peace because she knows she's innocent. her family supports her so she's not giving up. and lizz? well, she and her kids do their best to carry on without jaime or sandra. >> my daughter just loves her nana so much. and it was so heartbreaking. to tell her that nana wasn't coming home. >> reporter: when do you miss your dad the most? >> every day when i look at my kids. because i know what a wonderful grandfather he would've been. the jokes and the games and probably the toys he would've

made for them. >> reporter: they never got a chance to roll their eyes at a jim joke, huh? >> yeah. >> reporter: that's all for this edition of dateline. i'm craig melvin. >> i'm natalie morales. >> and this is "dateline." >> is your husband michael? i'm sorry to tell you, ma'am, he's been killed. >> no. no. no no. >> she's like candy, attractive on the outside but taedeadly one inside. she was pure evil. >> he fell in love with her. he thoughtn she was the be all end all. >> she had everything she wanted, but she longed for one thing more. >> i'm