looking for that love right until the hours before the winds began howling and the waters rose. >> that's all for this edition of "dateline." this is "dateline." >> i called my mom immediately. i just cried. i cried. i couldn't feel. my body went numb. i told her "karlyn's gone. she's gone." >> reporter: she was a beautiful young mom doing important work. >> she was an intelligence specialist. >> some of her work was very sensitive, top secret? >> i believe she had top secret clearance. >> reporter: when she was found dead, everyone wondered, did her work cost her, her life? >> i remember them telling me,

"did she come into a lot of money that she couldn't explain?" >> maybe she was selling secrets? >> maybe. >> that's, like, out of a spy novel! >> reporter: what about other secrets, the personal kind? >> we knew they were having issues. >> right before they got married, she found out that he was cheating. >> reporter: but somewhere out there was a stranger keeping secrets too. >> my data guy starts going through her facebook. >> she made reference to firearms in her social media. >> we saw that they were communicating her gas mileage. what a weird thing to do. >> reporter: a mystery that would drag on for months and then. [ gunshot ] one final secret, uncovered by science. >> you start peeling the layers back with acid until the number is visible.

she had a job she loved. a baby daughter she adored and her life ahead of her. she was shot dead in her home. her killer thought he covered his tracks. exposing a plot, it defied imagination. >> reporter: across the spectrum of love is there any more precious than that of a mother for her daughter? ♪ you are my sunshine our story tonight is about that maternal tie that endures from generation to generation. it begins in a military town near the mexican border. del rio, texas, a small city anchored by the laughlin air force base. karlyn ramirez grew up there.

she was an easy going child says her mom, susan garcia ramirez. >> karlyn, when she was young, she was real calm and quiet. karlyn loved to sing. she would sing all the time. ♪ whenever she was out with her friends, you know, she would sing for them. >> reporter: rosanna flores was one of those friends. what was it about karlyn that you wanted to be her friend? >> her smile, her voice. a very big heart. i can honestly say she never saw any bad in anyone. >> reporter: her friends anais ibarra and valerie mckechnie say it wasn't all about singing. >> we would go to the -- the local bar here, and we would dance. >> reporter: and they say the dancing could literally happen anywhere. that's karlyn in black. >> i was, like, fun -- fun times at the walmart parking lot. >> reporter: only in a small city, right? she went to college in del rio,

started in nursing and then transferred to criminal justice. nothing that prepared her mom for what she did at 22, enlist in the army. >> she didn't ask me. she didn't get my opinion. she told me after she had done it. >> reporter: your family is a military family? >> we are. my dad was air force. my sister is retired air force, and then i was in the army reserves. >> reporter: after specialty training in information technology, the army sent karlyn to south korea. off-duty she found time to give back. >> she found herself volunteering at an orphanage. >> reporter: that's so nice. >> she starts -- well, she starts sending me pictures of a little boy that she's in love with, and she says, "mom, i want to adopt him." i said, "no." >> reporter: in korea, karlyn found another kind of love, she began dating a handsome sergeant named maliek kearney. >> she was attracted to his confidence, to his air, and the way he carried himself. >> reporter: he was a decorated soldier? did she like that about him? >> yes. >> yes, they worked out together

and they ran. they were very competitive. >> reporter: karlyn gushed about maliek to her friends. >> she said that he was a great man, that he treated her right, and then she told me they were engaged. >> reporter: engaged and expecting. pregnant, the army transferred her to fort meade, maryland, home of the national security administration, and one of the nation's most secret and secure facilities. was she happy? was she excited? >> she was excited. she started working and absolutely loved it. >> reporter: top secret, some of it? >> she would say, "mom, i can't share anything about what i do"" >> reporter: meantime, the army moved maliek to fort jackson, south carolina, where he trained recruits in chemical warfare. the couple was 500 miles apart. while living by herself in maryland, karlyn became friends with another soldier, marissa manthe. marissa loved working with karlyn. >> she was the light of the office. she was loving. everyone loved her. >> reporter: marissa was a

single mom with a young daughter, so when karlyn was nearing the end of her pregnancy, they decided to share a house together. >> it had a backyard. it had a decent sized kitchen, and it was right by base. >> reporter: did you ever have security concerns about the townhouse or the area? >> we did have. karlyn had mentioned that she came home one day, and felt like stuff was moved around in the house. >> reporter: really? >> yeah. >> reporter: if somebody says that to me, i'm -- >> yeah. >> reporter: i'm getting worried. the two women kept the doors and windows locked, and worked together to make their townhouse a home. marissa helped karlyn set up a nursery, and then, on april 23, 2015, kattaleya vale ramirez was born. grandma susan was on the first flight from texas. what was it like for you seeing karlyn, and her new daughter vale together? your baby's -- >> yes, it was amazing. >> i got her, and i wouldn't share her with anybody. >> reporter: vale was healthy and beautiful.

karlyn radiant. their townhouse was filled with the joyful sounds of karlyn singing to vale. she particularly loved, "you are my sunshine." ♪ you'll never know dear how much i love you ♪ >> she was happy. it looked like she found her purpose in life. >> reporter: three months after vale was born, karlyn and maliek married in a small ceremony in south carolina. after the party karlyn went back home to fort meade in maryland with the baby. she said it was hard, the distance and not seeing him all of the time. susan stayed in touch with her daughter. >> i spoke with karlyn every day. sometimes twice a day. >> reporter: but tuesday, august 25 would be different. susan called karlyn that morning -- >> and she doesn't answer. >> reporter: is that, i mean you two have such a close relationship. >> that's unusual. so i waited, and i called her again, and she didn't answer. so i sent her an email to her work email. never got a response to that. called her on my lunch break, and she didn't answer, and i

said, "if you do not call me back or message me, i'm going to call the police." >> reporter: a now frantic susan reached karlyn's commanding officer at his home. he promised to have someone on the base find her. >> i hang up with him and i put the phone down, and i hear a ruffle our front yard we have river rock, and so i looked out and i saw three uniformed soldiers. >> reporter: oh, gosh. that -- >> and i knew. >> reporter: that just made me -- >> yeah, sick. that's what it did -- >> reporter: sick. >> to me too. >> reporter: ugh. it's what any relative of somebody in the military dreads. i mean, i'm a marine corps.s wife myself. >> that's the last. >> you don't ever want to have to see that. and -- i yelled my husband's name. and i just -- i dropped to my knees, and i said, "something happened to karlyn." and then they knocked. >> she was right, something had happened to karlyn. now this mother was about to

hear the words every military family dreads. >> reporter: what did they say? >> "we regret to inform you." just like they always say. >> when we return, what the soldiers said next would leave this mom horrified and confused. >> i couldn't even imagine what could have possibly happened. broken windshield... take 1... hey guys, my windshield just got broken, i feel like i need to blow off some steam. let's go... 1, 2, 3, 4... mr. blanks? there's no need to be stressed. geico makes it easy to file a claim online, on the app, or over the phone. yeah, but what if i never hear back? that's gonna make me want to go jab...jab! nope! your geico claims team is always there for you. that makes me want to celebrate with some fireworks. 5,6,7 go... boom, boom, boom, boom boom boom boom boom

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susan ramirez's husband opened their door to an army casualty notification team, and the worst news imaginable. their karlyn was dead. what did they say? >> "we regret to inform you," just like they always say. the same words. they had a chaplain with them, and they couldn't give me any specifics. i asked for the baby. they said that she was in the hospital. >> reporter: so what scenarios are running through your mind? >> i couldn't even imagine what could have possibly happened. >> reporter: the answers would come seventeen-hundred miles away, at karlyn's townhouse in maryland. homicide detectives kelly harding and dan myers of the anne arundel county sheriff's office were on the case. >> a maintenance person saw a dog walking around into an open back door of the town homes. he called 9-1-1, and the officers got there. and karlyn ramirez had been murdered. >> reporter: patrol officers lead the detectives to a second

floor bedroom, and an appalling scene. it was karlyn and her 4-month old daughter. together. >> she was laying in the master bedroom, and a little girl was -- they thought initially also had been murdered, but it turns out that she was just sleeping alongside her mom. the baby was unharmed. >> reporter: the investigators began their search for clues with karlyn's body. >> she was laying on the floor, near the crib. her pants and her underwear had been removed. >> reporter: did that suggest to you that there may have been a sexual assault? >> it's something that you have to consider. >> reporter: the crime scene investigation ramped up. csi's dusted for fingerprints, and collected hair and dna samples. karlyn had been shot three times. ballistics experts traced the bullets trajectory and recovered a bullet from the floor. they were able to narrow down the weapon to a few different models. >> the caliber of the projectile was .357, .38 special.

>> reporter: of course, a hard look at the spouse is homicide investigation one-on-one. so, the day after they found karlyn's body, detectives flew to south carolina to talk with maliek. >> he'd been placed in an interview room and he was waiting for us. >> reporter: they started by asking about karlyn. >> what can you tell us about her? >> she was the love of my life. >> reporter: maliek's superior officer had given him only the vaguest of details about what happened to karlyn. >> he tell you how she passed away? >> they said, "you guys would answer all my questions." i don't know what happened. i still miss her. >> maliek, she was murdered. >> why? >> that's what we're hopin' you could help us with.

>> i don't know. i didn't know anybody that didn't like her, had anything against her. >> reporter: they wanted to know maliek's whereabouts the day of the murder. he told them he worked his usual shift monday, leaving around 2:00 p.m. he said he stayed in his apartment until he reported for duty tuesday morning. >> didn't go out monday night, go anywhere, talk to anybody? >> no, i mean, i stayed home, text on my phone. stuff like that. >> reporter: the questions got personal. detectives had been told karlyn was planning to divorce maliek. >> i'm telling you, as an outsider, it looks like y'all were done. she was done with you, right? she had moved on. >> i didn't know. >> reporter: they'd learned about a brief relationship karlyn had with another soldier at fort meade shortly before she married maliek, and asked him how he felt about that. >> it was before we were married, and i forgave her, and i told her, "i forgive and forget. >> you ever cheat on her when

you were in a exclusive relationship with her? >> cheat? no. >> reporter: the detectives cut to the chase. >> you didn't kill her, right? >> no. >> did you have somebody else kill her? >> no. >> reporter: was he being really cooperative with you? >> he appeared to have nothing to hide. >> reporter: maliek let them download his phone, and that wasn't all. he volunteered his bank records, offered fingerprints, and provided a dna sample. he gave police permission to search his apartment and car. the detectives got to work. >> right away, we talked to neighbors that -- in his apartment building. they said that his car never left. >> reporter: maliek kearney's apartment and car, a distinctive jaguar xjl, came up clean, and all his electronics, his cellphone and netflix account put him at home that night. 500 miles from the crime scene. police checked toll plazas and license plate readers between south carolina and maryland. there was no sign of maliek's jaguar anywhere on what would

have been a 15-hour round trip. would you say that he had a good alibi? >> yes. >> reporter: maliek kearney was free to go. the maryland detectives were back to square one. at the beginning of what would become an incredibly complex homicide case, an investigation that would span a half-dozen states, involve hundreds of witnesses, multiple government agencies and a mountain of forensic evidence. >> coming up. could karlyn's top-secret work have cost her, her life? >> i wondered if she was targeted, or knew something she wasn't supposed to know. >> i remember specifically them telling me did she come into a lot of money she couldn't explain? get a hobby. you should meditate. eat crunchy foods.

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>> reporter: a little more than a week after she was killed, private first class karlyn ramirez was buried with full military honors. flags were presented to her parents, husband and daughter. susan had little time to mourn. she was busy caring for karlyn's daughter vale in texas while her father, maliek, was on active duty in south carolina. susan was also doing everything she could to help solve the case. investigators asked again and again, who would want kalryn dead? >> i would say, "you know, i am racking my brain.

and i wish i could tell you, but i -- i just cannot think of anyone." >> reporter: detectives cast a wide net. they spoke with karlyn's roommate, marissa, multiple times. they were curious about the soldier karlyn had the brief relationship with before she married maliek. could her death have been the result a love triangle gone bad? >> their line of questioning made me think that they were looking at the soldier that she was involved with. >> reporter: the guy she was having the fling with at work? >> yes. >> reporter: what kind of questions did they ask about him? >> what the relationship was like. did he love her? did she love him? did maliek know? >> reporter: did you have to check into this soldier that she had the little side thing with? >> certainly, and he was devastated that this happened. he provided his phone. his whereabouts. we concluded that he was telling the truth, where he was during the time. >> reporter: with the boyfriend cleared, some of karlyn's

friends and family thought the murder might be connected to her top secret work at ft. meade. >> i wondered if she was targeted, or knew something she wasn't supposed to know because of her job. >> reporter: the detectives were looking for any sign that karlyn might have been recruited as a spy by foreign agents. >> i remember specifically them telling me, "did she come into a lot of money that she couldn't explain to you?" "no, she didn't." >> reporter: maybe she was selling secrets? that's, like, out of a spy novel. >> yes, yes. >> reporter: that theory. what did you learn about karlyn ramirez's role in the military? >> she was a intelligence specialist. >> reporter: did you have to explore the fact that maybe this has something to do with her job? >> there was no evidence of a handler, or any sort of misbehaving with her information. >> reporter: espionage was ruled out. weeks went by without a break in the case. >> our homicide detectives are still conducting interviews. we're still processing evidence from the scene. >> reporter: the crime scene investigation intensified. >> they had my house taped off for almost a month.

just going through evidence, going through the house, trying to find things. trying to find leads. >> and marissa lived in fear, remembering karlyn's concerns about someone creeping around their townhouse. >> reporter: karlyn had said she thought maybe somebody had moved things around. did your mind go at all to the possibility that it could've been someone random? >> it even almost seemed like a hitman had did it, because it was so meticulously planned out. >> karlyn's roommate told us that they had security concerns. that someone had maybe been in the townhouse at -- at some point. >> it was always something we kind of kept in the back of our minds. >> reporter: did you have to consider the possibility that maybe karlyn had a stalker, someone who was watching them, watching her? >> yeah. we -- it looked extensively into her background and into her communication. >> reporter: investigators pursued the few leads they had. all the while, susan was pushing them for answers. >> two or three times a week, you know, they would hear from me.

>> reporter: it must've been getting frustrating that she was murdered, her killer is out there, and her daughter is with you. you must've just felt that fear. >> constant fear. vale was not out of our sight. >> reporter: but she heard nothing. in april, on what would have been karlyn's 25th birthday, the family took vale to visit her grave. >> happy birthday mommy. >> reporter: by that time, maliek was living nearby. the army had allowed him to transfer from south carolina to fort sam houston. he had gotten orders to get closer to the baby. and as close as he can get was san antonio so he can come and spend time with the baby on the weekends. the ramirez family struggled to find normalcy. back in maryland, the investigation seemed to have stalled. anne arundel county offered a $20,000 reward for information about the case. the reward generated no promising leads, and homicide detectives wondered if karlyn's

death could be part of a larger, even more sinister crime. coming up -- investigators pursue a stunning new theory. >> there's no likely suspects. so the first thought is, serial killer or some unknown individual. >> reporter: and then, an eye-brow raising revelation about karlyn's estranged husband. >> she said that they had been intimate, for several years. com? almond breeze starts here with our almond trees in our blue diamond orchard in california. my parents' job is to look after them. and it's my job to test the product. the best almonds make the best almondmilk. blue diamond almond breeze. special guest flo challenges the hand models to show off the ease of comparing rates with progressive's home quote explorer. international hand model jon-jon gets personal. your wayward pinky is grotesque.

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good evening. the united states closed out 2020 with the deadliest and most infection month of the pandemic. 77,000 lost their lives to covid-19. 6.4 million contracted the virus. the u.s. has had more than 20 million covid cases. senate democrats along with the independent senator sanders pushed again without success for

the senate vote on $2,000 stimulus checks. back to "dateline." welcome back. police cleared her exboyfriend and phone records showed her husband was hundred of miles away when she was shot. it was time to broaden the search for answers. investigators make a remarkable discovery buried in a trail of electronic clues. >> reporter: it had been months since karlyn ramirez had been found murdered at home with her infant daughter in her arms. with all leads exhausted, homicide detectives wondered if karlyn's death might be part of a pattern. they reached out to profilers with the fbi's behavioral analysis unit. fbi special agent jonathan shaffer would join the team.

>> the story is that the husband's in south carolina. there's no apparent likely suspects. so the first thought is, serial killer or some unknown individual. that's where they'd requested the profilers. >> reporter: had there been any serial killers in the area that could possibly tie to this then? >> no, there -- there wasn't at -- at that time. it was a longshot. >> reporter: did this lead anywhere? contacting the bau? >> their opinion was that probably somebody close to her did this. >> reporter: with no obvious progress in karlyn's case, friends began to despair. >> it scared me that karlyn was never gonna get her justice. >> reporter: but what they didn't know was maryland detectives and the army's criminal investigation division had been quietly collecting a massive amount of electronic information. of course, police had initially talked to karlyn's estranged husband, maliek, but his phone records had indicated he was at home, 500 miles away when karlyn was murdered.

but, months after they'd asked for it, police finally had not only maliek's data, but the data of everyone who had been contacted from his phone. >> we then requested and received information from the people that maliek was communicating with. >> reporter: all their tedious digital searching paid off. it was a development that took them in a whole new direction. buried in maliek's phone records were numerous calls and texts with a woman named dolores delgado, a former soldier living in florida. investigators pored over her phone records, a dramatic discovery. >> we had learned that dolores was actually in south carolina during the time of the murder. >> reporter: that phone data not only had dolores in south carolina, it placed her in maliek's apartment complex. this must've been a big break. >> this was a huge break. >> reporter: on a wednesday afternoon in march

2016 detective harding turned up unannounced on dolores's doorstep in cocoa beach, florida. >> knock on the door, and i say, "hi. i'm detective harding. i'm from anne arundel county, maryland. i'd like to talk to you." and -- >> reporter: that's a shock. >> -- and she was very shocked, and she said, "about what? maliek?" and i said, "yes actually." >> reporter: in an interview room at the sheriff's office, the detective asked dolores about the night of the murder, if she was in maliek's apartment, and, if he was with her. >> she admits that she was there that night. >> reporter: what happened at maliek kearney's house? >> she was in the living room, and he went to bed. as far as she knew he was there the whole time. >> reporter: was this a sexual relationship? >> she said that they had been intimate, you know, for several years. >> reporter: so she's the long-time paramour. >> they definitely had a long relationship. >> reporter: the detectives now knew one thing for sure after talking to dolores delgado, maliek kearney had lied to them.

about being faithful to karlyn for starters. >> do you have a girlfriend now? >> no. >> reporter: but most critically, about what happened the night of karlyn's murder. >> didn't go out monday night, go anywhere, talk to anybody? >> no, i mean, i stayed home, text on my phone. if you have somebody that can account for your whereabouts during the time of the murder why wouldn't you offer that to us? why would you keep that secret? >> reporter: the detectives had to consider that maybe maliek just didn't want to admit he was cheating on his wife with dolores. they took a closer look at this girlfriend, who'd told them she and maliek hooked up when they were both serving in kuwait years earlier. then, when harding and myers examined dolores' phone data they learned she also lied, about owning a gun. >> she told me that she was almost ignorant about firearms, but in her phone i could see that she was looking for a very particular firearm.

>> reporter: on her phone there was a text that read," my last .357 i paid 400. so i wanna stay in that range." detective myers dove deeper into dolores's life. >> my data guy here starts going through her facebook. >> there were some things going on with firearms, some information about where where she purchased firearms previously. >> reporter: this is the woman who had no knowledge of firearms. >> right. >> reporter: the posts led myers here, to a gun shop near dolores' home. the shop had a sales receipt and a federal firearms transaction record for a taurus .357 revolver. both forms were made out to dolores delgado. the revolver dolores bought matched the caliber of gun that had killed karlyn. >> we saw that this gun was one of the ones on the list. >> reporter: of itself, this purchase of gun wasn't a smoking gun, but the detectives had to wonder why dolores would lie to them about owning a weapon, and there was something else.

myers soon learned that dolores had put a box of .38 caliber ammunition up for sale on facebook. >> now that's obviously can't say it's the same bullets. but it matched all the characteristics. >> reporter: all this sleuthing took months, and while the detectives were working, dolores moved to san antonio, texas into an apartment not far from maliek kearney. 150 miles west, on their farm in del rio, karyln's mom knew nothing about this new person of interest, despite staying on the detectives. >> it's me again. i just don't want you to forget my daughter because she was very much loved. >> reporter: the investigation now encompassed a half-dozen states. maryland detectives and fbi agents were homing in on dolores delgado. what were all learning about the relationship between maliek kearney and dolores delgado? >> just how, for lack of a better term, weird it was. they -- they were friends. they were friends with benefits. they were lovers. but not really romantically

involved, they were just sort of, best friends with a romantic bent. >> reporter: there was another weird thing. dolores delgado's phone was full of texts between her and maliek kearney that weren't on his phone, and what a twisted story those texts would tell. >> coming up. a tip from a complete stranger, could blow the case open. >> he said, "one night, we got rid of a gun. i think that was your murder weapon." >> this is pretty remarkable. >> when dateline continues. introducing a revolution in the world of pain relief:

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♪ we are farmers. bum-pa-dum, bum-bum-bum-bum ♪ (burke) start with a quote at 1-800-farmers. >> reporter: it was a bittersweet day in august, 2016 when karlyn ramirez's loved ones celebrated her life on the first anniversary of her murder. back east, lead detectives kelly harding and dan myers had developed two prime suspects -- karlyn's husband, maliek kearney and his long-time mistress dolores delgado. as they studied the couple's text messages, the detectives found something curious. maliek had wiped a lot of texts off his phone that still existed on dolores's phone.

her texts made them look at the night of the karlyn's death in a whole new light. >> we saw that they were communicating her gas mileage. you know, what a weird thing to do. >> reporter: not only that, they were talking gas cans as well. the detectives had dolores's bank records, which showed a purchase at this florida home depot. >> we were able to get a copy of the receipt of her purchase which included two -- two gas cans. >> reporter: finally, they saw the pieces of their puzzle coming together. at the start of the case, harding and myers thought it was unlikely that maliek would have been able to travel all the way to maryland, kill karlyn, and return undetected. but this new evidence changed everything. >> take us through what you believe happened that night. >> dolores is providing all of the tools, the firearm, the ammunition, a vehicle and really, the important alibi of her staying and -- and using his phone. >> reporter: the detectives saw it as an elaborate plot.

dolores was in maliek's apartment pretending to be him. texting on his phone and streaming his netflix account, creating an electronic alibi, while he killed karlyn. this scenario explained why they didn't find maliek's jaguar on any license plate readers. if he did that long drive in dolores's car, and carried extra fuel to avoid gas station security cameras, there wouldn't be any trace of him. >> so he drives straight there. you believe he kills karlyn ramirez relatively quickly? >> at the most he woulda been there for ten minutes. >> and then turns around and -- >> goes back, and only stops the one time. just on the roadside, in a dark area, to fill up the car. and then immediately gets back in the car and continues to drive. >> how cold-blooded this was. >> he had a will the of time along the way to say never mind.

what am i doing? this is crazy. driving eight hours by yourself with your own thoughts in a car. you have a lot of time to change your mind. he was determined. >> reporter: thirteen months after karlyn's death, maliek kearney and dolores delgado were arrested in san antonio. >> outta the blue, i get a phone call at work. and they ask me if i could come to san antonio that evening. and i said, "for what?" they said, "there's been an arrest in your daughter's case." but he didn't tell me who. >> reporter: susan and her husband made the long drive across west texas. >> that's when i first met the federal prosecutor. they're the ones that -- that told me that -- that maliek had been arrested. and -- and his girlfriend -- >> what were you learning about dolores? >> i didn't know anything about her. she was no one. she was no one to me. >> reporter: assistant u.s. attorneys jim warwick and ken clark met with dolores and maliek. >> i introduced myself to mr. kearney.

>> and you also got a chance to speak with miss delgado? >> we presented to her the facts that we had, and the evidence that we had complied against her at that point in time. >> reporter: after the arrests came a new lead. a tip to detective harding from an ex-boyfriend of dolores's in florida. >> he called me and said, "hey, one night i was hanging out with dolores, and we got rid of a gun." and he said, "i think that was your murder weapon." >> i mean, do you get calls like this every day? this is pretty remarkable. >> i wish. but we don't. >> reporter: investigators met with the tipster in merrit island, florida. he said that not long after karlyn's murder, he and dolores delgado had burned some clothing and sneakers here. and that wasn't all. he said he destroyed a revolver for her -- dismantled it. and that the two of them threw the pieces of the gun off this pier.

an fbi dive team out of miami was soon on the scene. the water was gin-clear that day, and divers found forensic sunken treasure. there on the bottom -- rusted, covered with seaweed, and encrusted with barnacles -- were the pieces of a handgun. the parts were rushed to the fbi crime lab in quantico, virginia. "dateline" was given rare access to the fbi's world renowned crime lab. in his first ever interview, firearms expert brett mills told us how he examined and reconstructed the weapon. first, he carefully cleaned the frame of the gun. >> when i finished cleaning it, there was no serial number there from our reference collection, i -- i knew where the serial number should be. >> reporter: it was gone because delgado's ex-boyfriend had ground it away -- totally obliterated it or so he thought. mills had a plan. >> we call it "serial number restoration."

there are still compressed layers underneath that still has that impression of the serial number. using acid, we can restore that number. >> reporter: he demonstrated the process on a gun from the fbi collection. >> once you've polished it, you go in, and you literally start peeling the layers back with the acid until the number actually is visible. >> it's amazing how it just reappears, the serial number. >> sometimes it does. other times, you might not be able to restore any type of number at all. >> reporter: there was another way to determine if they had found the murder weapon. mills would try to match the tell-tale markings on the bullets that killed karlyn to the gun from the river. >> these fine striations that you see are the equivalent of a human fingerprint. >> reporter: but there was no way the recovered weapon would ever fire again. so mills removed its barrel, gently cleaned it, and attached it to a working revolver for a test firing.

he demonstrated that process with a similar revolver. mills was able to do six test firings with the recovered gun. everything he found was added to the evidence. now, prosecutors would have to see if it would hold up when the defense pointed the finger at someone else in baltimore federal court. coming up -- trial begins. could a major twist, tip this case? >> it was right before christmas. >> so it was like an early christmas present? >> yes. >> reporter: and then -- the verdict and the emotional fallout. one of the worst things about a cold sore is how it can make you feel. but, when used at the first sign, abreva can get you back to being you in just 2 and a half days. be kinder to yourself and tougher on your cold sores.

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welcome back. malik was charged in the shooting death of his wife carlin. authorities were convinced he and his girlfriend had an elaborate coverup screheme. investigators found phone records and what they suspect was the murder weapon. the case was headed to court where a surprise witness was about to take the stand. here is andrea canning with the conclusionalibi". in august of 2013, malik's trial began in federal court in baltimore. he was charged with interstate travel for the purpose of domestic violence resulting in

death. the trial would be the caome nation of a three-year investigation that gathered thousands of pieces of electronic and physical evidence in an extraordinary forensic effort. prosecutors wanted to see him not as a super star army sergeant but killer, a soulless executioner who took her life because she wanted to divorce him and endangered his baby daughter believing her in her dead mother's arms. >> he was used to getting what he wanted. relationships could end with malik but they had to end on his terms. >> they show the jurors digital evidence. >> there was electronic data including text messages and photo messages she shared. >> including photos she sent of

her odometer and driving range. >> one particular message was important. he's test firing the gun and he texts her saying this gun is so darn loud. >> this was part of the prosecutor's plan to put her gun in his hands. the serial restoration test he did on the gun recovered from the river. >> i wound up pulling up all by one of the digits. it wound up matching the bill of sale for ms. delgado's purchase of the revolver. >> is that a bingo for you? >> finding out the number i restored was basically the same one on her bill of lateen was awesome. >> and mills had something else to tell the jury. remember, he done a test firing like this one through the barrel of the recovered gun.

what happened when you test fired bullets and compared them to the bullets from the crime scene? >> we identified three bullets being fired from the revolve recovered from the creek. >> the prosecutors introduced the interrogation video. >> i love this woman. i loved her. i love her to death. >> we did that so that the jury would realize that he was being untruthful. >> do you have a girlfriend now? >> no. >> no, okay. >> there was something on the tape that prosecutors wanted to be sure jurors noticed. >> incredibly stupidly he never actually asked how did my wife die? do you want to know what happened to her. >> you told me she passed away. >> but the u.s. attorneys knew their case would hinge on whether jurors believe their star witness dolorus delgado. she agreed to cooperate. >> it was right before christmas.

>> so like an early christmas present. >> early christmas present for 2016, yes. >> prosecutors argued that malik's long-time mistress would do anything for him. on the stand, she backed that up. dolorus testified how she gave malik her gun, her car, the gas cans and packed him a sandwich for the drive and provided him with that crucial electronic alibi. in your directive, you said malik wasn't home that night, was he? she answered no. was that the beginning of the end for his alibi? >> it is. placing him at a location other than where his phone was was critical for this case. >> the prosecution rested. the defense argued they didn't prove anything. they argued someone else did it, that maybe jurors should take a closer look at the government's star witness dolorus delgado.

it was her gun disposed by her boyfriend that killed carlin and with ca arrlin out of the way, have malik to herself. they showed a text sent before carlin's murder. crazy bitch is going to be put out but the jurors didn't buy it. they quickly found malik guilty. carlin's mother had been in court every day. how did that feel hearing -- >> i was so glad because with the guilty verdict, i don't have to worry i'll have any dealings with him. >> at his sentencing, the judge called malik a predator and sentenced him to life plus another ten years on top of that. he's appealing his conviction. dolorus was sentenced to 17

years for her part in the crime. why do you think malik and dolorus did this? >> i think malik killed carlin because she was the first woman in his life that was willing and able to stand up to him and he couldn't handle that. as far as dolorus, she was a pawn that she would just kind of do whatever he said. >> it was important to carlin and the baby and the ramirez family to bring them some justic justice. >> with the trial behind them, the ramirez family and carlin's friends focus on raising vail and teaching her about her mother. ♪ you are my sunshine my only sunshine ♪ >> she sang to her when she bathed her. she sang to her when she dressed her. >> vail could still hear that loving voice. carlin's sister put a recording inside a teddy bear.

♪ you'll never know dear, how much i love you ♪ >> we are at this point the constant in her life. we want her to feel protected, loved, everything that i know her mom would have given her. that's all for this edition of "dateline." i'm natalie morales, thank you for watching. i'm craig melvin. >> i'm natalie morales. >> and this is "dateline." if you admit that she's never coming home, it's like you're admitting defeat. or that she's dead. >> a hard working life, a loving mother and a woman with a complicated love life. >> working and spent sometime after hours together. >> kathy was trying to break off the relationship. >> the secret was out. replaced by a