if i could talk to her right now? if that little sliver of hope is still out there. i'm going to bring you home. somehow, some way, i'm bringing you home. we've said it every time. we're not giving up. never going to give up. it doesn't matter what it takes. everything else takes a backseat. it really does. life does not go on. people around you, life goes on. but you're still stuck. you're holding on to the hope. that's all for this edition of "dateline." i'm andrea canning. thank you for watching. [music playing] hello, i'm andrea canning, and this is "dateline."d ha. we used to tell each other that if somebody ever tried to hurt us, we would do everything

we can to leave something behind, so the other one can figure it out. i believe that she was murdered. this is a very bizarre death. andrea canning: it was baffling from the start-- a young woman, dead, at her millionaire boyfriend's mansion. my heart started racing. you found her hanging. i did. andrea canning: detectives ruled it a suicide. but was it? at the scene-- knives, ropes, a cryptic phrase. mary zahau-loehner: her hands were tied. her feet were tied. she was naked. this was sending a message. andrea canning: that wasn't the only suspicious death here. dina shacknai: no mom wants to hear that her son was a victim of a homicide. something happened at the top of the stairs. andrea canning: what really went on in that mansion? hear from the man at the center, in his first television interview. you thought you had nothing to hide. i knew i had nothing to hide.

the worst shock in, probably, my entire life. hello, and welcome to "dateline." victims' families have often described their feeling of loss simply as surreal. and so it was for both the shacknai and zahau families. their tragedies were tangled into one riveting mystery that captivated the nation. at the center of the story-- two puzzling deaths and lingering suspicions. the search for the truth would pit the families against each other in a battle, sparking more questions than answers. here's josh mankiewicz with "the mansion on ocean boulevard." josh mankiewicz: some places feel secluded, insulated, secure. dina shacknai: i can remember saying that and feeling that, and saying, nothing bad

could ever happen here. josh mankiewicz: here is coronado, california, just over a bridge from san diego-- a town of beautiful beaches, people, and homes, like this one on ocean boulevard-- except that in the summer of 2011, this mansion became ground zero for a mystery. this is a very bizarre death. there's no doubt about it. josh mankiewicz: well, actually, there's been plenty of doubt and plenty of theories. my sister was dead. and did a lot of thing go through my mind? yes. josh mankiewicz: secrets-- both suspected and imagined. is it possible that other people know more than they're saying? yes. josh mankiewicz: it's certainly possible. beyond that, it's hard to say for sure, especially when it seems everyone has a story to tell. and those stories lead to accusations, often with zero proof. people are going to believe what they want to believe,

with no evidence. josh mankiewicz: paradise valley, arizona, was home for the shacknai family. but the summers they spent in coronado were special for dina and her son, max. dina shacknai: max loved the beach. he loved the water. and he used to tell me on the way to coronado, mommy, this is our place. josh mankiewicz: she and max's dad, jonah, met in 1997. dina shacknai: we had an instant connection. it's very rare you meet someone like that. josh mankiewicz: they married in 2001-- a second marriage for jonah, who was already the father of two. he'd gotten rich owning a pharmaceutical company, called medicis. she went back to school to get a phd in developmental psychology. and then, along came max. and then, along came maxie. he's almost to the edge. oh, my, he did it! [gasps] how do you feel, max shacknai? josh mankiewicz: he was an active kid who loved sports and performing for his mother

and her camera. mom! this is my song, right? dina shacknai: it is, yeah. josh mankiewicz: during one of those summers in coronado, the mansion on ocean boulevard was on the market. and i said, well, let's just go by and look. josh mankiewicz: they bought it in 2007. but soon, there was trouble in paradise and a bitter divorce in 2009, when max was four. they shared custody and worked to be civil, and it wasn't long before jonah met someone new. dina shacknai: maxie he told me about it, and i said, well, maybe i should meet her. and he said, that would be great, mommy. josh mankiewicz: rebecca zahau was 32, born in myanmar. she'd moved to the us in her 20s. you were ok with her spending time with max. well, max said he had feelings for her. he liked her. at that time, i had no concerns, because i trusted that jonah-- based on our history, max would be safe there.

josh mankiewicz: and safe in coronado, where nothing bad is supposed to happen. josh mankiewicz: july 11, 2011, max was staying with his dad and rebecca. dina was in coronado, too, at a home just down the street. that's when jonah called her. dina shacknai: he said, dina, you've got to get here right away. josh mankiewicz: as rebecca explained it to police, jonah had been at the gym. six-year-old max was home with her. rebecca said she heard a crash and found max on the floor near the staircase. the mansion's heavy chandelier had fallen to the floor next to him. rebecca said max wasn't breathing, and she started cpr. rebecca's 13-year-old sister, xena, who was visiting, called 9-1-1. josh mankiewicz: police and paramedics arrived within minutes. jonah called dina from the hospital.

and he tells me, thank god that she was able to give him cpr. i think to myself, my god, like, thank you, thank god. he's going to be ok. he's going to be ok. josh mankiewicz: max was unconscious. dina and jonah took up a vigil at the hospital. jonah's brother, adam, flew in from his home in tennessee. you came out to support jonah. correct. how well had you known max? i knew max well. he was a really wonderful kid. josh mankiewicz: at max's bedside, jonah asked one of the doctors for his prognosis. dr. peterson looked at him and said, well, i don't know. i don't know. i'm not sure if he's going to walk or talk. that sounds like about the worst news you can get. dina shacknai: but it wasn't real. i would have bet my life on it at that time that max was going to be ok. josh mankiewicz: there was more bad news on the way.

what had happened in that house? police uncover some disturbing clues. coming up-- they located a female on the property. the victim's hands and feet were bound. i guarantee you, my heart started racing. andrea canning: who was this victim? andrea canning: soon, detectives would be investigating not just one puzzling death here, but two. dina shacknai: it was the worst shock in, probably, my life. andrea canning: when "dateline" continues. finish ultimate, engineered for the toughest conditions. dry, burnt-on stains, old dishwashers, very hard water. finish ultimate with cyclesync technology helps deliver the ultimate clean. (♪♪)

life has twists and curls. but you define them and make them bounce. tresemme flawless curls defining mousse.

24 hour. hydrating curl definition. style your life the way you want. ♪♪ tresemme, style your way. let's go boys. the way that i approach work, post fatherhood, has really been trying to understand the generation that we're building devices for. here in the comcast family, we're building an integrated in-home wifi solution for millions of families, like my own. connectivity is a big part of my boys' lives. it brings people together in meaningful ways.

♪ ♪

josh mankiewicz: the early morning hours of july 13, 2011-- as family members kept a vigil by the hospital bed of six-year-old max shacknai, a breathless man called 9-1-1. josh mankiewicz: once again, police raced through the streets of quiet coronado island. and once again, their destination was the mansion on ocean boulevard. jonah's girlfriend, rebecca, was staying there. jonah's brother, adam, had spent the night in the guest house. you wake up, you walk out. tell me what you see. a woman, hanging. at the time, i didn't necessarily think to myself,

oh, my goodness, she's bound or whatever, but just, rebecca's hanging. josh mankiewicz: naked, bound hand and foot, rebecca zahau was hanging by the neck from a second-floor balcony. i said, i guarantee you, my heart started racing. this is actually happening. josh mankiewicz: even as he called 9-1-1, adam says he thought she was dead. but you tried to do something. i tried to do something, absolutely. and it was not-- never even occurred to me that somebody would look at this as, like, a crime scene or something like that. i mean, that was the furthest thing from my mind. so you cut her body down? yeah. josh mankiewicz: and? uh, started cpr. to no avail. to no avail. when the coroner units arrived at the scene,

they located a female on the property, who appeared to be deceased. josh mankiewicz: rebecca's sister, mary zahau lohner, was hundreds of miles away in missouri when her husband, doug, came to her work to bring her the awful news. i remember him saying, rebecca's gone. and-- and i said, what do you mean? i just talked to her last night. josh mankiewicz: in that phone call, rebecca told her sister about what happened to max. it was the same story she told police. mary zahau-loehner: she said she was in the bathroom, and she heard a loud noise, a loud crash. and when she came out, max was there on the floor. and the chandelier was close to him, and he was unconscious. how'd she describe jonah during those days? that he was upset. and it broke her heart to see him upset. josh mankiewicz: they'd met when rebecca worked for an eye doctor, and jonah was a patient. he came in for an appointment, and-- that's correct. josh mankiewicz: --talking, and next thing you know, they're going out. apparently, yes.

um-- you are making an expression that makes me think that you thought that wasn't a particularly good idea. i never approved of the relationship, if that's what you're asking me. because? first of all, he is almost twice her age. josh mankiewicz: her free-spirited sister fell for jonah anyway. did they seem happy? they seem in love? i think my sister loved him in her way. to her, she was somewhat in awe of him, i think, to a certain extent. josh mankiewicz: mary says that while rebecca and max were close, rebecca gave the impression she didn't get along well with max's mom. and when max had his fall, mary said, rebecca worried how dina would react. she was upset about it. and she said, dina is going to kill me. she said dina's going to kill me. that's correct. rebecca seemed upset? stressed? you get any sense that she blamed herself for what had happened? she seemed stressed, but not inappropriately so.

because everybody was stressed. everybody was stressed, and i actually sympathized with her and maybe even mentioned that of, just, got to be tough on you. how terrible. josh mankiewicz: soon, rebecca's death became national news, in large part because of details revealed by sheriff's investigators. the victim's hands and feet were bound, and she was completely nude. it has yet to be determined if this will become a criminal matter or will remain as a death investigation. josh mankiewicz: in other words, did rebecca hang herself, or was someone else involved? a neighbor reported hearing screams the night before. was that rebecca? there was a scream that somebody heard. you hear that? well, my windows were closed. i did not hear a scream. josh mankiewicz: meanwhile, at the hospital, dina says she was only focused on max. she kept watch by his bedside, willing him to open his eyes.

it was saturday, july 16, 2011, five days after max's fall. dina shacknai: and i noticed that his eeg was just flat. and i thought-- i thought the machine was broken. and i'm shaking the machine, and i'm thinking, it's not working. it's not functioning. i'm shaking. and then, i'm saying, you know, the eeg machine is not working. the eeg is not working. josh mankiewicz: but it was working. six-year-old max was gone, and dina was devastated. (crying) i mean, it was the worst shock in, probably, my entire life. josh mankiewicz: a mother, in shock and in mourning, but also questioning, how exactly had max's fatal fall happened? others ask what led to rebecca's hanging. the mystery at this mansion was only getting deeper. andrea canning: coming up-- ropes, knives, a curious phrase at the scene.

there was a message painted in black paint on the door leading to the room. andrea canning: but to some, the most curious thing of all-- the police theory of what really happened. this is a very unusual circumstance. we conducted an experiment to determine if it is possible for a person to secure their hands behind their back in the fashion we found. andrea canning: when "dateline" continues. take an ekg from anywhere, but with 6-times the data. can your smartwatch do that? introducing kardiamobile 6l, the fda-cleared ekg that provides six-times more heart data than any smartwatch. and it detects three of the most common arrhythmias in just 30 seconds, including atrial fibrillation, bradycardia and tachycardia.

kardiamobile 6l, the world's most advanced personal ekg. get yours today at kardia.com or amazon. can you save water using a less than full dishwasher? we do it every night... do it with cascade platinum plus. one load of dishes in the sink uses 24 gallons of water while a dishwasher uses less than 4 per cycle. so do it with cascade... the surprising way to save water.

josh mankiewicz: so doin july, 2011,de... a private funeral was held for six-year-old max shacknai in arizona. just a few days later, rebecca zahau was laid to rest in missouri. back in coronado, the mansion on ocean boulevard was the focus of overflowing numbers of both questions and rumors. there's roughly 200 years of experience in the sheriff's homicide unit. they all agree this is a very unusual circumstance. josh mankiewicz: rebecca was found hanging, naked, bound, hand and foot. if it was suicide, it looked like a highly unusual one. and remember, rebecca was in the house when max shacknai fell. right now, we don't see any connection between the two incidents. the sheriff's department investigated for two months. coronado held its breath. then, at a news conference, sheriff bill gore laid out the facts as his investigators saw them.

was max's death a homicide? the answer is no. it was a tragic accident. was rebecca's death a homicide? again, the answer is no. it was a suicide. josh mankiewicz: sergeant dave nemeth said the evidence told a sad tale in which one tragedy led to another. when rebecca checked her voicemail just before 1:00 am, sergeant nemeth said, she heard a grim message from her boyfriend-- max's dad, jonah. that message that was left on her phone was to inform rebecca of max's grave condition and imminent death. josh mankiewicz: did rebecca blame herself for the child's severe injuries, and then take her own life? the sergeant showed photos from inside the bedroom where rebecca spent her final moments. there was a rope tied to the bed. the other end had been looped around rebecca's neck.

there were also two knives in the bedroom, apparently used to cut the rope. everything was swabbed for dna. dave nemeth: dna profiles were only from rebecca. josh mankiewicz: so what about rebecca's hands and feet being tied? didn't that show another person was involved? sergeant nemeth said it did not. we conducted an experiment to determine if it is possible for a person to secure their hands behind their back in the fashion we found. josh mankiewicz: they even showed a video demonstration. and while tying one's hands in a suicide is uncommon, the medical examiner said it's not unheard of. people do it. the thinking is that they bind themselves, so that they won't change their mind midway through. it's unusual at first glance, but it does happen. josh mankiewicz: the location of the apparent suicide note was also uncommon. dave nemeth: there was a message painted in black paint on the door leading to the room. i am going to show you a picture of the door. we will not be revealing what the message said.

josh mankiewicz: the investigation left some people unsatisfied-- none more so than rebecca's family. i know in my heart she did not commit suicide. josh mankiewicz: also unsatisfied-- dina shacknai. sheriff's investigators illustrated their findings with this graphic. they said max was riding his scooter on the second-floor landing, somehow fell over the railing, then hit or grabbed the chandelier, and took it down with him. that sounds to me like, is max some sort of a stuntman? bruce lee? that's ridiculous. why is it ridiculous? he's six years old. kids that age do crazy things. when i was seven years old, i jumped off the roof of the garage, holding an umbrella as a parachute. no. no. i'm absolutely positive. he was a very smart six-year-old. he was very athletic. he was very coordinated, and he was a very careful person, a thoughtful person. josh mankiewicz: dina didn't just insist something wasn't right. she opened her checkbook and hired her own experts,

including dr. judy melinek, a respected forensic pathologist who reviewed the autopsy report and photos, and who also disagreed with the official conclusion. judy melinek: max had too many injuries to be explained with a simple accidental fall. josh mankiewicz: dr. melinek thought max's injuries indicated he'd been assaulted before he fell. what's more, she questioned whether the fall itself could have happened as the sheriff's department described it. measurements showed the railing was 32 inches high. six-year-old max was only 45 inches tall. judy melinek: his center of gravity was too low. even on the razor scooter, his center of gravity is too low to go over that banister. josh mankiewicz: it all pointed to a chilling alternate scenario. according to dr. melinek, someone assaulted max, and then he somehow went over the banister. in other words, this was a homicide. i would much rather have them to say, you know what?

this was an accident, and here's why. no mom wants to hear that her son was a victim of a homicide. josh mankiewicz: and if someone killed max, dr. melinek's theory focused on one person. i think rebecca was somehow involved. but how much she was involved, and to what degree, she took that to the grave. josh mankiewicz: that alarming suspicion was only the beginning. because it wasn't just dina who was investigating. rebecca's sister, mary, was equally convinced rebecca would never hurt max or kill herself out of guilt. two women coping with terrible tragedies, neither willing to accept the sheriff's department's conclusions. mary was about to make some incredible accusations, and she wouldn't back down. could rebecca have been killed? a second autopsy magnifies the mystery. coming up-- some deep bruising and internal bleeding, which couldn't be explained by the hanging.

but could be explained by what? by somebody knocking her down from behind and hog-tying her-- something along those lines, a struggle. andrea canning: a twist was coming. josh mankiewicz: did you have anything to do with rebecca's death? absolutely not. you thought you had nothing to hide. i knew i had nothing to hide. andrea canning: when "dateline" continues. subject 1: who's coming in the driveway? subject 2: dad! dad! dad, we missed you! daddy, hi! subject 3: goodness! my daughter is being treated for leukemia. i hope that she lives a long, great, happy life and that she will never forget how mom and daddy love her. st. jude, i mean, this is what's keeping my baby girl alive. announcer: you can join the battle to save lives by supporting st. jude children's research hospital. for just $19 a month, you'll help

us continue the lifesaving research and treatment these kids need-- now and in the future. subject 4: cancer makes me feel angry. not in the feel on the outside, just the inside i'm angry at it. subject 5: when your kid is hurting and there's nothing you can do about it, that's the worst feeling in the world. announcer: 1 in 5 children diagnosed with cancer in the us will not survive. subject 6: those that donate to st. jude, i hope that you will continue to give. they have done so much for me and my family. announcer: join with your debit or credit card now, and we'll send you this st. jude t-shirt that you can proudly wear. [speaking spanish] subject 7: are you ready to go have some fun?

subject 8: yeah! subject 7: yay! subject 9: when we came here, we didn't know what tomorrow would hold. st. jude showed us that tomorrow there's hope for our little girl to survive. announcer: let's cure childhood cancer together. please donate now.

i am christina ruffini with the top stories. police are investigating a suspected terror attack. truck rammed into a bus stop near a military base. one person was killed and more than 30 injured. a spokesperson for mcdonald's said e. coli was found in samples of their beef patties and ruled that out as a source of the outbreak. they have step getting onions from the facility that is likely the source of the contamination. for now, back to dateline.

a zahau's hanging a suicide. but neither max's mom nor rebecca's sister were convinced. each woman suspected foul play, and one of them was about to make an explosive accusation. continuing with our story, here's josh mankiewicz with "the mansion on ocean boulevard." josh mankiewicz: the official investigation was over. the crime scene tape and evidence markers-- long gone. that said, an unofficial search for clues was just beginning. online message boards buzzed with theories from the far-fetched to the implausible. through it all, rebecca's sister, mary, didn't buy the official finding of suicide. was she fragile? was she easily upset? is she the kind of person who would fall apart after a crisis? not at all. josh mankiewicz: so when detectives said that voicemail, the one jonah shacknai left for rebecca

with the grim news about max, may have caused rebecca to hang herself, mary wasn't having it. i was not about to have my sister's name smeared and the world remember her as this crazy woman who committed her suicide because of a phone call. josh mankiewicz: was all this just about how rebecca would be remembered? after her death came some revelations, things even mary hadn't known about-- like in 2005, in california, when rebecca didn't show up for work and just vanished. her boyfriend reported her missing to the local police department. rebecca turned up a few days later, saying it was just a misunderstanding. you're persuaded that if she did sort of mysteriously disappear back then for a day or two, it was something that she willingly did, and not some sign of mental fragility? i really don't know what happened at that time.

josh mankiewicz: now, she said, she needed to know how rebecca died. she had rebecca's body exhumed, and media-friendly forensic pathologist dr. cyril wecht performed a second autopsy. his conclusion-- homicide. was rebecca murdered? her family thought so. and eventually, the case found its way to this man. it was intriguing from the beginning. josh mankiewicz: san diego attorney keith greer. keith greer: dr. wecht did identify some deep bruising and internal bleeding, which couldn't be explained by the hanging. wait one second. it couldn't be explained by the hanging, but could be explained by what? by somebody knocking her down from behind and hog-tying her-- something along those lines, a struggle, a struggle. josh mankiewicz: plus, greer says the force of falling feet from the balcony should have caused more severe injuries to rebecca's neck. greer, like dr. wecht, believed someone killed rebecca, and then placed her body

at the end of the rope. and he began to develop a theory as to who. the writing on the door is the key to the case. josh mankiewicz: remember the message painted on the bedroom door? sheriff's investigators initially declined to reveal what it said. greer eventually found out, the message scrawled in black acrylic paint read, "she saved him. can you save her?" greer believed the message was not written by rebecca. it was written about her. who'd she save? she didn't save max. she saved max. she did save max. at the time, you have to look at this in context. josh mankiewicz: remember, rebecca said she did cpr on max after he fell. so at the time those words were written, max was still alive. max was alive. and maybe because of her efforts. it wasn't maybe because of her efforts. it was exactly because of her efforts. and that's why it's the key to the case. because i know, whoever committed the murder knew that rebecca had saved max. josh mankiewicz: it was, he said, a small circle--

mostly, family. i had an eyewitness who put dina shacknai at the scene of the murder that evening. josh mankiewicz: dina, the grief-stricken mom-- could she have blamed rebecca, and then sought revenge? remember, mary recalled her sister saying, dina's going to kill me. where were you when rebecca zahau died? i don't know what time rebecca zahau died-- during that time. but i was at the hospital all night. josh mankiewicz: in 2013, keith greer filed a civil wrongful death lawsuit on behalf of the zahau family. based on his eyewitness, he named dina as a defendant, along with her twin sister, nina. there was also a third defendant-- the man who called 9-1-1, jonah's brother, adam shacknai. did you have anything to do with rebecca's death? absolutely not. josh mankiewicz: greer disagreed.

he pointed to those knots tied around rebecca's wrists and ankles. figuring 'em out in the first place is really hard. tying them-- almost impossible. josh mankiewicz: greer believed whoever tied the knots had to be an expert, possibly, a sailor. and adam shacknai worked on the mississippi river as a tugboat captain. when he ties things off, he uses a figure eight, and then closes it with a single hitch or two. guess what knots are tied on both her legs and her hands? figure eights, tied off with a single hitch or two. josh mankiewicz: sheriff's investigators had questioned adam extensively after rebecca's death. you didn't hold anything back from investigators. nothing. you helped them to the extent that you could. yeah, exhaustively. you thought you had nothing to hide. i knew i had nothing to hide. josh mankiewicz: and when investigators determined there was no evidence placing adam at the scene--

they cleared you. they did. did you think this was over at that point? yeah, i did. josh mankiewicz: it wasn't over. rebecca's sister was determined to hold someone accountable. i'm guessing that somebody said to you that filing a lawsuit, a civil lawsuit, to find answers in a criminal matter is generally an extremely unsatisfying way of pursuing justice. that may be, but my only recourse was the lawsuit. josh mankiewicz: soon, they would start to get answers, just not the ones they expected. andrea canning: coming up-- where was dina the night of rebecca's death? keith greer: this eyewitness was adamant. he was very clear, no doubt about it. andrea canning: powerful new video evidence, and the dna evidence-- where was it? adam shacknai admits that that morning, he cut rebecca down. he loosened the ropes on her wrist to check her pulse.

he gave her mouth-to-mouth resuscitation. and there's no dna. zero. andrea canning: when "dateline" continues. growing old is part of the journey, even when you have heart failure. but when he had shortness of breath, carpal tunnel syndrome, and lower back pain, we wondered, could these be warning signs of something bigger? thank goodness we called his cardiologist because these were signs of attr-cm, a rare and serious disease... ...that gets worse over time. if you see any of the warning signs, don't wait, ask your cardiologist about attr-cm today.

business just to keep the lights on. you're here to sell more today than yesterday. you're here to win. lucky for you, shopify built the best converting checkout on the planet. like the just one-tapping, ridiculously fast-acting, sky-high sales stacking champion of

checkouts. that's the good stuff right there. so if your business is in it to win it, win with shopify. sleep more deeply and wake up rejuvenated. purple mattresses exclusive gel flex grid

draws away heat, relieves pressure and instantly adapts. sleep better. live purple. visit purple.com or a store near you today josh mankiewicz: seven years after the death of her son, max, dina shacknai lives alone in the arizona home she once shared with her family. how are you even standing upright today? max, my son.

my love for him was so great. we were a perfect fit. we were lucky. i still feel lucky. even though he's gone. yeah. josh mankiewicz: in the years following max's death, dina continued to investigate, and hired a woman named tara schneider. you're convinced that max died, not as the result of an accident, but a murder. yes. homicide. josh mankiewicz: tara has no law enforcement background. she calls herself an intelligence analyst. she and dina have floated several theories over the years. the current theory-- whoever killed max, it was not rebecca zahau. these days, their suspicion is focused on information from a neighbor that's never been verified-- a story of a wild party at the mansion the night before max's fall. he has not been interviewed by the police, and he's not come forward. but what connection it might have to max's death-- you have no idea what that is. i don't. but i think it should be explored.

josh mankiewicz: she said police never spoke with the neighbor, but we did, and he doesn't remember anything about a party. and max's dad, jonah shacknai, who was in the house that night, told us there was no party. jonah says he never doubted the official investigation, but wanted to rebut the theories offered by dina and others. his lawyers hired the highly regarded investigative firm, kroll. the resulting report says, the evidence is consistent with an accidental, tragic fall. and there is no evidence of foul play, malice, or other non-accidental occurrence. how many people said to you, you need to let this go and move on? many. so many. josh mankiewicz: even if she'd wanted to move on, it really wasn't possible. because dina, remember, was being sued by the family of rebecca zahau, who blamed dina, in part, for rebecca's death. through it all, dina stuck to her story--

that she'd been at max's bedside at the hospital the night rebecca died-- even though the zahaus' attorney, keith greer, had an eyewitness willing to testify that he saw dina outside the mansion that night. keith greer: and this eyewitness was adamant. he was very clear, no doubt about it. and turned out to be dead-bang wrong. and turned out to be wrong. josh mankiewicz: in april 2017, after four years of litigation, this security camera video came to light. it's from the hospital where max shacknai was being treated, the same night rebecca zahau died. clearly visible-- dina shacknai. at some point, you look at that footage from the hospital, and you realize, i'm wrong, and my witness is wrong. dina wasn't there. she was at the hospital, provably. absolutely. i got mad. i got really mad. josh mankiewicz: greer called a press conference to publicly eat some crow. keith greer: when these pictures come out, though, you can't refute 'em. josh mankiewicz: he removed dina from the lawsuit,

along with her sister, nina. and the zahau family attorney apologized to you. was that enough? he made a public apology. and i would say that not as many people saw the public apology as who saw continuous accusations against us. josh mankiewicz: greer pushed forward anyway, with just one defendant-- adam shacknai. that says, to me, this is some scattershot attempt, and you are pursuing everybody that comes into your line of sight, looking for a sympathetic jury. that's it. and a lot of people looked at it that way. why shouldn't that shatter the credibility of the rest of your case? i think the reality of it is that we always had adam involved, all through the process. josh mankiewicz: in the lawsuit, greer outlined quite a detailed and unsubstantiated narrative. he argued, rebecca was killed not to avenge max, but instead, during a sexual assault. greer's theory is that it began when rebecca stepped out of the shower and found adam in her bedroom,

watching her. she then gets uncomfortable and tries to escape. she screams for help, about 11:30 that night. josh mankiewicz: greer says that explains the screams heard by a neighbor. right after that, to silence her, adam hits her on the back of the head, knocks her at least partially unconscious. then he has time to think, and he grabs the black paint, and he paints this phrase on the door. josh mankiewicz: "she saved him. can you save her?" if i'm going to kill somebody and try to make it look like a suicide, i'm not going to write a cryptic phrase behind. i'm going to write a phrase that says, "i'm sorry, i'm guilty, i did it." it wasn't staged to be a suicide. josh mankiewicz: even greer says evidence placing adam at the scene is weak. adam shacknai have any marks or scrapes or cuts on him that would suggest he'd been in a struggle with someone? none. none. josh mankiewicz: same with adam's dna. it's pretty hard to get rid of your dna. hard to get rid of dna. all right?

adam shacknai admits that that morning, he cut rebecca down. he loosened the ropes on her wrist to check her pulse. he gave her mouth-to-mouth resuscitation. he gave cpr pumps to her chest. and there's no dna. keith greer: and how much dna and how many fingerprints are found on the knife, the rope, her body? how much? none. zero. zero. josh mankiewicz: zero of adam's, that is. rebecca's dna and fingerprints were everywhere. according to greer, that means adam, who had no criminal history, knew exactly how to wipe down the scene, somehow removing his own fingerprints and dna, but leaving just rebecca's. of course, it could also mean that adam simply wasn't there when rebecca died, which is exactly what law enforcement came to believe. i'm guessing that if you walked into court on any case and opposing counsel said, there is no evidence here,

there is no fingerprints, and there is no dna, and that is the proof of the case that i am bringing, you would think to yourself, i got a ground ball here. the absence of evidence isn't the evidence of absence. and so we know it's murder, because it's wiped down. we know it's not suicide. josh mankiewicz: would a jury agree? greer had to prove adam shacknai was somehow responsible for rebecca's death, that his own actions made him liable. in a wrongful death civil case, the standard is, more likely than not-- a significantly lower bar than beyond a reasonable doubt, which is the standard in a criminal case. it is, however, still a challenge. and when the case went to trial, keith greer would be up against a top-notch defense team. you feel overmatched? i was so outgunned, it was pathetic. two families connected by tragedy prepare to go head-to-head in a courtroom. coming up-- josh mankiewicz: did you attack her? no. did you sexually assault her?

no. did you tie those knots on her body? no. andrea canning: would a jury believe him? i sat down next to mary, and said, mary, i'm sorry. this is probably not good news. andrea canning: when "dateline" continues.

welcome back. rebecca zahau's death had been ruled a suicide, but her sister, mary, was convinced she'd been murdered by adam shacknai. adam insisted he tried to save rebecca after finding

her hanging from a balcony. now, the two were facing off in a civil lawsuit. a jury would decide who was responsible for rebecca's death, and the verdict would leave both sides stunned. here's josh mankiewicz with the conclusion of "the mansion on ocean boulevard." adam shacknai: the plaintiff's attorney got-- he's got a good imagination. josh mankiewicz: adam shacknai says it's simple. he had nothing to do with the death of rebecca zahau. were you present when rebecca died? no. did you attack her? no. josh mankiewicz: did you sexually assault her? no. did you tie those knots on her body? no. josh mankiewicz: are those the kind of knots that only a sailor or somebody who worked around boats in the water would know? no, those are common knots. josh mankiewicz: sheriff's investigators found no evidence adam was present when rebecca died, and they cleared him. that didn't stop rebecca's family from suing in civil court.

the lawsuit, the long string of accusations-- what do you think is going on here? it's denial. it's-- they don't want it to be seen that their sister committed suicide. josh mankiewicz: we asked rebecca's sister, mary, about that. a lot of times, families do not want to admit that someone committed suicide, because they blame themselves for not, maybe, having seen the signs. is that what you're doing here? no. and i have been accused of that multiple times, including the sheriff's department. is it possible that rebecca was depressed and you missed it? no. josh mankiewicz: in march, 2018, the wrongful death lawsuit began in san diego. defending adam was dan webb, a former us attorney and a veteran of many courtrooms. there'll be no evidence that shows that adam shacknai had anything to do with the death of rebecca zahau. josh mankiewicz: in particular, no dna or fingerprints from adam

were found at the death scene. plaintiff's attorney, keith greer, called several experts, who testified that the lack of physical evidence could show adam had cleaned up after himself. there was nothing on the doorknobs whatsoever, and-- as far as prints. keith greer: again, that's consistent with it being wiped down? yes. josh mankiewicz: and a handwriting expert who looked at that message on the door. the writing on the door is more-- more comports with adam than it does with rebecca. josh mankiewicz: greer also claimed rebecca had been sexually assaulted with a knife prior to her murder. his expert testified a steak knife found in the bedroom had her blood on the handle. greer said the sheriff's department overlooked that evidence. that's nowhere in any of the sheriff's records. they never considered that. they never analyzed that. josh mankiewicz: the defense called a forensic technician, who testified she did find the blood on the knife, and with it, a simple explanation-- a recent cut on rebecca's right hand.

and when greer asked her if the blood could have come from a sexual assault-- i didn't see any evidence of that. josh mankiewicz: no evidence-- a point the defense hammered home. i saw no fingerprint evidence that was identified or directed towards adam shacknai. of all the items i tested, he was excluded on all the items. josh mankiewicz: adam's brother, jonah, took the stand. he called rebecca's death, "unfathomable," but said adam was not responsible. dan webb: is there anything that adam's ever done in his life that would cause you to believe that he ever would have done the acts that he's accused of in this case? never anything. it's inconceivable. josh mankiewicz: adam took the stand, too. keith greer: did you hit rebecca on the head? i never hit rebecca on the head, or anywhere else, for that matter. keith greer: and then, did you devise this scheme to try and cover up your wrongdoing by painting this saying on the door and making it look like she had been hanged by someone else?

absolutely, positively not. josh mankiewicz: the case went to the jury. did you feel confident as deliberations began? i felt we could possibly win very convincingly. josh mankiewicz: less than four hours later, a verdict. keith greer: i sat down next to mary, and said, mary, i'm sorry. this is probably not good news. josh mankiewicz: this was it-- a decision. and even keith greer would be in for quite a plot twist. number one, did adam shacknai touched rebecca zahau before rebecca zahau death with the intent to harm her? the answer is yes. number two, did that touching cause the death of rebecca zahau? the answer is yes. josh mankiewicz: yes, meaning that the jury found adam shacknai responsible for rebecca zahau's death. i just broke down. i was just like, ok, i'm not crazy. i'm not the only one who believes

that adam murdered my sister. josh mankiewicz: that's not quite what the jury said. finding someone liable in a civil case is not the same as finding them guilty of murder. what's more-- the verdict in this case did not have to be unanimous, and it wasn't. nine jurors found adam responsible. three did not. the jury did award the zahau family $5 million. courtrooms are supposed to be a place where justice is dispensed. was this about justice? no, it wasn't. josh mankiewicz: since this wasn't a criminal case, adam didn't go to jail. he returned home to tennessee and filed a motion for a new trial, which was denied in january, 2019. then, in february, adam's insurance company and rebecca's family reached a settlement of $600,000, and the case was dismissed. after the civil trial, the sheriff's department took a fresh look at rebecca's death. eight months later, that review also concluded

that rebecca died by suicide. dina shacknai would like to see authorities reinvestigate her son's case. do you think they will reinvestigate max's death? i think it's the right thing to do. do i think it will happen? i really don't know. josh mankiewicz: how does a mother ever truly accept the tragic loss of a child? the ripples keep on spreading to this day, in a place where nothing bad was supposed to happen. that's all for this edition of "dateline." i'm andrea canning. thank you for watching. [music playing] hello, i'm andrea canning, and this is "dateline."ow? if i had to put it into one word, "numb" would be the closest.