be there. >> reporter: autumn had always intended to be a care-giver. her cousin, close as sisters, sharon king, remembers that even as a little girl she administered playtime tlc. >> we had a doctor's office. and our patients were our stuffed animals. >> and dr. autumn klein was holding clinic hours, huh? >> she was the doctor. >> reporter: it was an interest that took root early for autumn and never left. always a top of her class student in the baltimore area, she later got her undergraduate degree in neuroscience from amherst. >> helping people was the main thing. she was just so smart, so intelligent, so thoughtful and so caring. >> you and -- and your husband must have been very, very proud of her. >> we were. >> reporter: lois klein is autumn's mom. >> we knew that she was putting her mind on her studies, and we were giving her the best education we could possibly give her, and she was taking advantage of it. >> reporter: med school was a certainty. autumn announced she was heading to boston. her mother worried the city's

crime-rate was too high. >> she said, "i'm goin' to boston university medical school." and i said, "no, you're not." and she said, "yes, i am." and i said, "no, you're not." and she said, "yes, i am." and she went to boston university medical school. she had a mind of her own. >> reporter: in medical school, autumn developed a romantic thing for a research colleague and he for her. robert ferrante, bob to his friends, held a phd in neuroscience and was hunting for cures to devastating brain illnesses like lou gehrig's and huntington's diseases. he was also more than 20 years her senior, divorced with two grown kids. >> i simply told her that that was a little bit too old for her. i didn't think that that was the right age. >> reporter: but two days before graduation from med school, a determined autumn, wasting no time, was walking down the aisle with her much older bridegroom. >> and what was your impression of him, sharon? >> i -- nice guy, a charming guy. a bit heady, you know? >> egg head? >> yeah. >> nerdy? >> yeah. [ laughter ] and she kind of was.

and she kind of wasn't, you know. >> reporter: the couple made a home just outside boston. in a few years, a baby girl arrived into their hectic lives. autumn took it in stride. >> a 2:00 a.m. diaper change is nothing for her. she's, you know, i mean, a 2:00 a.m. call from the hospital, "you have to come in to take care of this patient." you know, she's used to that. >> reporter: the new mother was becoming a sought-after specialist in neurological ailments in women. because of her expertise, she was interviewed for an educational video distributed by the discovery channel. >> women with epilepsy really need to be started on a seizure medication in advance of pregnancy. >> reporter: but autumn was growing frustrated with boston. and professionally she felt as though she'd crested there. that's when pittsburgh loomed into view. in 2011, the university of pittsburgh and its renowned sister medical center offered an ideal career move: for bob, a new research lab, for autumn a chance to head her own department.

>> autumn was not just a rising star; she was a shooting star. she was nationally recognized as a leader in her field at a very young age. >> reporter: but still something was gnawing at her, a kind of emotional vacuum. she wanted to have another child. by now in her early 40's, she was taking fertility treatments, hormone injections. but nothing was happening. >> was it really eating away at her that she wasn't getting pregnant, time was going by? >> yes. and, you know, just speaking from experience, fertility treatments are the loneliest place a woman will ever go. >> reporter: looking back, her mom, lois, recognizes now some worrisome signs. changes in her daughter. >> i kind of saw that she wasn't herself too much anymore, that she was kind of a little, what do you call it, kind of a little down, maybe, here and there. >> reporter: then in early

2013 the couple tried a new approach to the baby problem. a fertility doctor thought the body-building supplement known as creatine just might help autumn get pregnant. as it turned out her husband bob had been using the stuff in his research. so, on april 17th autumn klein seemed ready to give creatine a try. she texted her husband that day: "i ovulate tomorrow." he answered "perfect timing. creatine." smiley face. these are hospital security camera pictures that show autumn throughout the day and leaving work late that night. ten minutes later she was home. and minutes after that her husband bob ferrante was on the phone to 911. >> allegheny county 911, what's the address of your emergency? >> hello. hello. please please please! >> reporter: his wife slumped on the kitchen floor, gasping for breath. the dispatcher asked the husband what he was seeing. >> i think my wife is having a stroke. >> reporter: paramedic steve mason and his partner

arrived at the ferrante home to find a woman in very bad shape. >> she was lying on her back on the kitchen floor. her eyes were open and she was unresponsive. >> reporter: an hour after walking home from the medical center where she worked, dr. autumn klein, seen here in hospital surveillance footage, was back as a gravely ill patient in its emergency room. and whatever was happening to her was a medical mystery to the team trying to keep her alive. then they saw the blood. so neon red, so out of their experience. when we come back -- autumn is surrounded by some of the best doctors in the country. but no doctor can work miracles. >> to them, this was out of this world. just couldn't make sense of it. >> reporter: maybe someone else could. so, what brings you to jersey? well, geico's the #1 auto insurer in new jersey, new york and connecticut. so i just came by to say "thanks." #1, huh? that's great.

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>> reporter: dr. autumn klein had been rushed by ambulance to the er of the university of pittsburgh medical center after slumping to the kitchen floor of her home. >> we thought that there was definitely a possibility of a stroke. and we knew she was in critical condition. >> reporter: now the trauma team surrounding her was trying desperately to keep her vital signs going. >> reporter: reporter alan jennings with nbc's pittsburgh affiliate wpxi covered the story. he recounted what doctors later

said about that night. >> she had this blank stare in her eyes. barely a pulse. >> and they didn't know what had happened to her? happened to her? >> no, they didn't. >> reporter: autumn was struggling to breathe. >> and then in comes the ventilator. >> the ventilator, the machines are now taking-- >> machines -- >> --over. >> --taking over to -- to keep her alive so they can -- until they can determine what in the world was going on. >> at some point, alan, did they realize that this is one of their own? this is that brilliant, young doctor that works in the women's neurology unit? >> they did at one point. i don't know that they would have treated anyone any -- any differently. but she was one of them. one of the team. >> reporter: when autumn's husband, medical researcher bob ferrante, arrived in the trauma room, he tried to give the team some of his wife's medical history. he explained she'd been on fertility hormones. >> she had headaches, fainting spells, and that she generally was expressing that she hadn't been feeling well. >> reporter: he told the er doctors he thought his wife had suffered a stroke, though

diagnostic tests said otherwise. by then, bob ferrante had already called his father- and mother-in-law at their home near baltimore with the bad news. autumn's mother lois klein said they got in the car immediately to drive through the night to pittsburgh. she was counting out the exits. >> and i said, "please, let me get to frederick. then please let me get to hagerstown. please let me get to hancock. please let me get to pittsburgh." >> reporter: back in the er, a resident, trying to rally autumn's failing body, stuck an iv into her and noticed something quite odd -- her blood in his tube showed shocking red. >> and the observation of that doc at the bedside that, "this blood is too red. why am i seeing blood this brilliantly red saturation?" >> to them this was out of this world. just couldn't make any sense out of it. >> reporter: eventually, autumn went into cardiac arrest. doctors managed to bring her back, barely.

>> they actually took turns -- doing chest compressions to try to get some reaction from her, to try to get her heart -- moving and pumping again. >> reporter: another doctor reviewed autumn's symptoms and ordered up a test. he wanted a toxicology screen of her blood. hours passed. her blood was being pumped into a machine that was doing the oxygenating work of her heart and lungs. at some point, word had reached her cousin sharon, now living in washington state. sharon talked by phone to autumn's frantic husband bob and was grateful for his medical background. >> he was, you know, calling his colleagues. you know, he knows this neurologist or this person, this -- you know, "great." you know, "use your resources." you know, i had no idea what was going on. >> reporter: eventually, though, autumn lost brain function. by the time her parents finally made it to the hospital, they could see there was little hope for their daughter. >> they had a lotta tubes and things hooked up to her.

and i held her hand, and i talked to her. and i told her, "you heal everybody else's brain, why can't you heal your own?" >> reporter: sharon wanted desperately to fly out from washington state to see autumn. but her aunt lois told her to wait. >> that's my other half in that hospital bed. i need to be there. >> reporter: doctors managed to keep autumn alive for two full days. at some point, sharon could tell that autumn's grieving husband had run out of hope. >> and he did say to me, "i'm gonna go spend the last night with the love of my life." and at the time i thought, "it's not over yet." >> reporter: but in the er suite, everyone knew it was. autumn's little girl was brought to her bedside. >> she made some comment to somebody about, "i don't think mommy's ever gonna come home again."

>> reporter: on the third day after she'd been wheeled into the er, autumn's exhausted colleagues pronounced her dead and turned off the machines keeping her alive. >> a lot of my life feels like it doesn't make sense without her. you know, she was there for everything. >> reporter: autumn's husband and family now had funeral plans to make -- and even darker days to get through. but one person wasn't done with the mysterious case of autumn klein. his work was just getting started. dr. todd luckasevic, associate medical examiner for allegheny county, performed the autopsy on autumn. >> it was regarded as a sudden, unexpected death. >> reporter: which meant the county needed to figure out why this otherwise healthy woman was dead. there was no reason to suspect fertility hormones, vitamins or supplements, like creatine, could have led to her collapse. her brain showed no signs of a stroke. though an examination of the heart did reveal an abnormally shaped heart valve. >> it's a congenital anomaly

found in approximately 2% of the population. >> does it lead to early death? >> not in your 40's. you need to be symptomatic. >> reporter: at the conclusion of autumn klein's autopsy, the medical examiner was perplexed as to what killed this woman. >> i'm seeing a healthy, white female that for all intents and purposes, should be alive. >> reporter: on the form that asked for cause of death -- dr. luckasevic wrote "pending" -- no definitive answer. but in a few days time he would have more information. the blood work was back from the lab. autumn klein had suffered a very unnatural death. coming up. what exactly had killed autumn? >> i was shocked. and i couldn't say anything. >> reporter: or is the question -- who?

>> reporter: two days after allegheny county's associate medical examiner performed his autopsy on autumn klein, the phone rang. the voice on the other end was from the hospital. autumn's blood tests were back. dr. todd luckasevic was startled to hear what the lab found. >> lethal, deadly amount of cyanide. >> reporter: what did that tell you? >> that told me that i have a cause of death now. >> reporter: cyanide. the poison of the nazi death camps and the jonestown massacre of the '70s. lethal fast killing stuff, not a common cause of death. >> i have done approximately 3,500 cases in my career. and this is my first case of cyanide poisoning. >> reporter: the lab's toxicology work found cyanide levels of 3.35 milligrams per liter in autumn's blood. so this is a lot of cyanide. >> that is correct. >> reporter: still, he needed to confirm the results with his own tests. he wanted to re-examine autumn's remains to see if he could find cyanide in other

parts of her body. but by then, he had released it to the funeral home. >> reporter: so here's an, an easy solution. you go back to the body and you take a second look. >> would love to. when we got the phone call on tuesday that she had a lethal level of cyanide in her blood, i called immediately the funeral home, and she had already been cremated. >> reporter: but the me still had samples of autumn's blood. its toxicology unit performed its own test for cyanide. analyst alesia smith added a simple solution to the blood. if cyanide was present in the sample, it would turn the center well of this disc purple. she and luckasevic demonstrated what they found. >> this example that we used today is, is very representative of autumn klein's sample. it's, it's almost identical. >> reporter: sure enough, the sample changed color. >> her color change was a deep, kinda dark purplish-pink. and it was obviously positive for cyanide. >> reporter: does that saturation of color tell you got a lethal amount?

>> oh yes, definitely. any amount, even the one milligram per liter, even the light pink color change means there's cyanide there, a significant, toxic, if not lethal, amount of cyanide present. >> reporter: autumn klein had died of cyanide poisoning, no question about it, he said. he grew even more confident when he reviewed the details of how she had collapsed and suffered. cyanide, once ingested, can quickly starve the body of oxygen. >> so oxygen's on the blood, but it's not being utilized by the body. >> reporter: it was the trapped oxygen that had turned the blood in autumn's veins that vivid red. he also considered the 911 call. as her husband is begging for help, autumn could be heard moaning in the background. >> now she's, like, having a seizure, like she's, jesus christmas, sweetheart!" >> reporter: luckasevic says that was likely autumn struggling to breathe, another important sign that cyanide was in her system. he knew he had a bizarre death on his hands and contacted the police. >> i call the detectives and i let them know, "cause of death

is cyanide poisoning. you need to help me with a manner of death." >> reporter: he wanted to know if autumn had committed suicide or been poisoned, in other words, murdered. >> there was a note on my desk saying that the coroner's office had a woman come in who had a lethal level of cyanide in her system. >> reporter: cyanide poisoning. >> yes. >> reporter: how many of those have you seen in your career? >> this is my first one. >> reporter: soon autumn's mom was given the news about the blood results. she then called her niece sharon king out in washington. >> she said, "are you sitting down?" i was like, "okay." and she said it was cyanide. >> reporter: just like that. >> and i was shocked. and i couldn't say anything. i couldn't catch my breath. >> reporter: when autumn's colleague dr. karen roos heard about it, she knew, right away, her friend had suffered an agonizing death. >> as a medical professional, i know about how people die of cyanide poisoning, and i

couldn't dwell on that. >> reporter: and just as in an old agatha christie cozy murder mystery about a cyanide poisoning in the village, the inspector was about to call. pittsburgh's senior investigators were enroute to talk to robert ferrante. did he have any idea how cyanide found its way into the bloodstream of his late wife? coming up. a husband's theory of how, and why, his wife died. so what'd he say? "why would she do this to herself?" >> reporter: what was he suggesting? and did he know something that police didn't? ing neutrogena hydro boost water gel. instantly quenches skin to keep it supple and hydrated day after day. formulated with hydrating hyaluronic acid which retains up to 1000 times its weight in water. this refreshing water gel plumps skin cells with intense hydration and locks it in. for supple, hydrated skin that bounces back. new hydro boost.

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>> reporter: five days after doctors turned off the machines on dr. autumn klein, pittsburgh police detectives made their way

to the three-story brick house where she made a home with her daughter and husband, medical researcher robert ferrante. veteran detective jim mcgee took the lead. ferrante greeted him and his partner. >> we start talking to him, what he can tell us about what happened to his wife at that point. >> reporter: ferrante told the detectives how his wife had arrived home that night a little before midnight. >> and how she came through the door and just collapsed on the floor. >> oh, god. >> reporter: he then recounted what he'd told 911. >> i think my wife is having a stroke. >> reporter: he thought his wife had suffered a stroke. the detectives informed him he was wrong about that. >> we ask him if he knew that his wife died of cyanide poisoning. >> he kinda gasped and said, "why would she do this to herself?" >> why would she do that to herself? >> that's correct. >> reporter: to the cops the man looked visibly shaken. it seemed he was suggesting his wife had committed suicide. ferrante then told the story about autumn trying, and failing, to get pregnant. he said she'd recently been taking the supplement called creatine in the hopes it would

help with fertility. veteran detective harry lutton understood the late wife's emotional agony. >> she's trying to have another child. and that's a lot of stress on a woman when they're trying to have children and they can't have children. >> repor distressed state of mind have led to suicide? detectives had to consider that as a theory. but cyanide? that's an unusual way to kill yourself. and it's a hard-to-get poison. how could autumn have gotten her hands on it? >> well, we looked into the labs that, you know, where she worked. she didn't work in a lab. she worked with patients. >> she was a clinic doctor, right? >> yes. >> she was working hands on? >> yes. >> reporter: but there were others labs at the medical complex, labs stocked with poisons, including cyanide. maybe autumn wandered into one of those. detectives pulled hospital security cam footage from that last day. and here's what they saw. that's autumn as she's getting ready to leave work. she goes up a set of escalators, disappears for roughly six minutes before coming back down

and heading home. question, in those missing minutes from the camera's eye had she found her way into a lab with toxins? >> and maybe this is where she goes to get her hands on cyanide to inexplicably kill herself. >> that's correct. >> reporter: yet there was a problem with that scenario: a big one. the investigators learned that to get into any of those labs, autumn would have needed a special access card. >> is there any sign that she had a card swipe that put her in an area where -- >> no. >> another researcher, or somebody might have had cyanide? >> no. there's no card swipes at the time that she left work. >> reporter: the more they dug, the less detectives believed this unexpected death was a suicide. true, autumn was frustrated by her infertility, but disappointment was all it was, thinks her cousin sharon. suicide was never on her radar. >> that was not autumn. that was just not autumn.

>> reporter: family, friends and colleagues agreed. autumn was a woman with plans to live, not die. she had a daughter she adored and was scheduling vacations and new research projects just before her death. >> so if she didn't take it, and your theory is that she hasn't killed herself, the only place to go is homicide. >> that's correct. >> reporter: who would want to murder autumn klein? the spouse is almost always a suspect till they're not. but the husband here, bob ferrante, was a renowned medical researcher. he didn't seem to fit the bill. >> professional guy. >> yes. >> well regarded. they're don't seem to be any money issues in the household. >> that's true. >> reporter: in fact, the marriage of ferrante and klein appeared to outsiders to be a good one. still, detectives had to consider the husband's line of research. he worked routinely with toxins in his lab. but not with cyanide. more than a week after they first interviewed the husband, detectives began talking to his lab associates. >> the people that we talked to said that there was no research

with cyanide. >> reporter: yet detectives were just getting started with their investigation. they combed through labs and laptops, interviewed friends and colleagues, re-analyzed hospital footage. >> i think we -- once we got all that together, and got all the pieces of that puzzle together, we had our picture. >> reporter: a picture that revealed only one person who had the motive and the means to kill autumn klein. her husband, bob ferrante. though the evidence was largely circumstantial, three-months after autumn's death, the cops were ready to make an arrest. at the time, bob ferrante was visiting his sister in florida. pittsburgh p.d. detective lutton headed south to make the arrest. but when he got there, the sister said ferrante was gone. >> she said that he got a phone call from an attorney, and he got in a car and said, "i gotta go." and he left. >> did you think that dr. ferrante was doing a runner on you? he was trying to get away? >> yes. yes. i mean, we were told that he was

goin' to his attorney. but he's runnin' from us. he knew we were comin'. >> on your books, he's a fugitive? >> yes. >> reporter: but not for long. as it turned out, ferrante was on his way back to pittsburgh to turn himself in, says his attorney, when he was pulled over by state police in west virginia. >> reporter: and later handed over to pittsburgh authorities. police had their man. now they and the commonwealth of pennsylvania had to prove to twelve men and women that he was the right one. >> they heard a clean case? >> they heard a very clean case. >> reporter: to jeffrey a. manning, the judge who would preside over it all, the case against bob ferrante, far from a sure thing, could well leave jurors scratching their heads. >> and i'm not one for predicting verdicts, but i would not have predicted one here. >> it could have gone either way and you wouldn't have been surprised? >> that would be correct. >> reporter: coming up -- was jealousy a possible motive for murder? what had dr. ferrante discovered about his wife? >> if this was somebody that she

was remotely interested in, she would have told me. >> reporter: when dateline continues.

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university of pittsburgh and its medical center. at one time it all seemed enviable. >> did you think they were a good couple? >> yeah. yeah, i did. >> reporter: and then it all went so wrong. autumn -- dead from apparent cyanide poisoning. her husband now -- a year-and-a-half later -- standing trial for her murder. even to the presiding judge -- with years on the bench -- this was a first. >> you had -- a very intelligent man, who's accused of poisoning his wife. you have experts who argue with one another. and -- >> and tip-top good lawyering going on-- >> ver -- very good lawyering. very good experts. >> reporter: and it would be up to prosecutor lisa pellegrini to explain what drove an otherwise mild-mannered scientist to kill the wife he supposedly loved -- and in such a cruel manner. she opened by describing a man infuriated -- one losing control of his more successful wife who had in turn grown tired of him. >> reporter: nbc affiliate wpxi's alan jennings was in the courtroom. >> the prosecutors say that he was obsessed -- jealous.

that his marriage -- he realized he was gonna be dumped by his wife. >> reporter: the prose asserted that the marriage was in freefall at the time of her death. autumn believed her husband had emotionally checked out -- especially when it came to the issue of having another child. she more or less told her cousin sharon he was a cold fish. >> my husband's a psychologist. and she said, "i need you to ask him -- if there's such a gene as for compassion. because if there is, then bob is lacking it." >> wow. that just describes acres of sadness, doesn't it? >> yeah. yeah. >> reporter: the prosecutor showed an email autumn had sent her husband in the months before her death. she wrote: "i realize now i have been alone in this entire emotional journey." "i can't even speak to you without getting angry." >> did she ever say, sharon, "i'm gonna leave him," "this isn't working"? >> yes. she did -- >> she said that to you? >> --to me. she did to me. yes. >> reporter: and he was positively rattled to the core, said the prosecutor, when he found out autumn was texting and

emailing a male colleague she'd spent time with at a conference in san francisco. bob ferrante, said the prosecutor, suspected his wife was having an affair. autumn's cousin was certain that wasn't true. >> if this were somebody that she was remotely interested in, she would have told me. >> so, you don't think anything physical is happening, certainly. >> no. no. >> reporter: but as the prosecutors told it, the defendant believed otherwise. rather than shoring up a crumbling marriage, the embittered scientist -- his wife the new rising star -- came up with a cold-blooded solution. he poisoned her. >> the motivation. just jealousy. that if he couldn't have her, no one was gonna have her. >> reporter: ferrante, the prosecutor said, thought he could get rid of his wife quickly by slipping her cyanide. when she didn't die immediately he had to come up with a plan b -- to mislead the paramedics and doctors. the prosecutor played that 911 call.

>> i think my wife is having a stroke. >> the prosecution was establishing dr. ferrante's attempts to lead everybody that he encountered, starting with the 9-1-1 operator. and he said, "i think she's had a stroke." >> so steering it. >> steering it. >> reporter: then when autumn finally died, according to the prosecutor, ferrante said something that he thought would keep the cause of death secret. lois klein testified that her son-in-law said flatly he did not want an autopsy. >> i said, "i'm her mother, and i want an autopsy." >> because you wanted to know the cause of death? >> i said, "i can't believe you don't wanna know what happened to her." and his response was that -- people do that. they do autopsies, and then the people don't wanna know the results of it. so that was that. >> reporter: the prosecution had described a man who'd lost control of his wife -- killed her -- and then tried

desperately to cover it up. defense attorneys bill difenderfer and wendy williams. >> you get this picture of a jealous guy who's career is un -- is being eclipsed by his wife, thinks she's got a lover. and bang, she's dead. >> well, that's the spin that the commonwealth put on this thing. and obviously, we think the reality is that's not the case. >> reporter: they said the prosecutor's alleged motive here made for great melodrama -- but it was miles away from the truth. >> reporter: bob was very successful. huntington's disease, als, on the verge of some big breakthroughs. >> reporter: bob ferrante, they countered, was a brilliant researcher and a loving man devoted to helping his wife -- not hurting her. and to sell that image, they flabbergasted the courtroom by calling the defendant himself to the stand. >> so in this case, the defendant made that choice. i've often said that it's -- risky at -- at best. the minute the defendant takes the stand, we now have the government's proof versus the defendant's credibility. >> reporter: a gamble, his defense team said, ferrante was willing to make. he wanted jurors to see him for

the man he was -- one who loved his bright, complicated, wife. >> he wanted to help the jury understand what was going on in their marriage. and -- and, you know, tell them how badly his wife wanted to have a child. >> reporter: yes, he conceded, he had been a jealous husband -- for a brief moment. but then he and autumn had kissed and made up in the weeks before her death. >> they go on a trip to puerto rico with their daughter. as the neighbors describe, when they come back, they're glowing, they're in love, they're holding hands. those actions speak a thousand words. >> reporter: in the moments after his wife collapsed, he said, he honestly thought she was having a stroke. when she died, he wanted simply to honor her wishes -- and donate her organs. that's why he didn't want an autopsy. >> he was aware that if an autopsy is done, a full autopsy is done, it will destroy the ability to donate the organs, which was his wife's request. >> reporter: a loving and loyal husband to the end, according to the defense. not a mad scientist treating his

wife like a lab rat -- killing her with cyanide. speaking of which, they said, the prosecution's claim of how autumn died was all wrong. >> there is not evidence that my client had anything to do with her death -- let alone her death caused by cyanide. >> reporter: an age-old poison -- its connection to a medical researcher -- and his doctor wife were about to be analyzed beneath a very different kind microscope -- the unforgiving eye of the law. coming up. would someone as smart as dr. ferrante use something as obvious, and easy to trace, as cyanide? >> that's like me buying a shotgun, telling everybody, "hey i just bought a shotgun," and two hours later my wife is deceased from a shotgun shot. >> couldn't be that stupid -- >> he woul

>> reporter: the commonwealth of pennsylvania had tried to paint robert ferrante as a jealous husband driven by rage to poison his wife. how did he do it? prosecutors believed he slipped the cyanide inside a drink and gave it to her shortly after she came home that night. a theory, said judge manning, that was tough to prove. >> no one stood there with their two eyes and said, "i saw him put the cyanide in the drink and give it to her." no one said that. >> reporter: and that is a weak point in the prosecution's argument? >> of course it is. >> reporter: they wish they had it. but they didn't. >> of course it is. but keep in mind, circumstantial evidence, even though most people don't believe what it really is, is very powerful. >> reporter: prosecutor lisa pellegrini told the court that ferrante used his wife's vulnerability -- namely, her infertility, to trick her into taking cyanide that night. earlier in the day, autumn had sent him this text, "i ovulate tomorrow." he texted back, "perfect timing creatine."

creatine. >> creatine. >> reporter: this is the solution. >> this is it. >> reporter: ferrante, the prosecutor alleged, had convinced his wife that creatine could help her get pregnant. he whipped up a poison drink, knowing she'd take it as soon as she came home. the poisoned drink theory was corroborated by something told later to a doctor friend of ferrante. >> dr. ferrante told him. he said, "i don't know. she came home. i gave her her creatine drink. she drank it and she passed out on the floor." >> reporter: and no one may have been the wiser for it, if it hadn't been for a lab test that found a sky-high amount of cyanide in autumn's blood. subsequent tests, the prosecutor added, were also positive for the poison. associate medical examiner dr. todd luckasevic underscored that for the jury. what caused this woman's death was? >> cyanide poisoning. period. >> reporter: no doubt? >> no doubt. >> reporter: nor was there any doubt, said the prosecutor, as to who poisoned autumn. police discovered the defendant's laptop hidden in an office safe.

and inside it, a wealth of information that told them bob ferrante had indeed been a very busy researcher in the months before his wife's death. >> dr. ferrante was googling searches concerning cyanide, where to purchase it, how to purchase it, the effects on people. >> reporter: and he didn't stop there. the prosecutor said bob ferrante then made an interesting request to his lab associates, something later relayed to detectives. >> he goes to the purchasing person in the laboratory and he tells this person that he wants to order a bottle of cyanide. >> reporter: has he ever done that before, detective? >> never. >> reporter: better yet, the detectives explained, the doctor asked for the cyanide to be delivered overnight. and when is all this in relation to-- autumn's-- slumping to the floor in her home? >> two days prior.

>> reporter: two days prior? >> yes. >> reporter: ferrante, he said, had even left his fingerprint on the container which, interestingly to them, had 8.3 grams of cyanide missing. what, like a heaping teaspoon full, maybe, of cyanide? >> i think about a teaspoon full would be about eight grams. >> reporter: is that a lethal amount of cyanide? >> yes. >> reporter: prosecutor lisa pellegrini said the defendant thought he was so smart, fooling his wife, and then everyone else by using a poison he assumed was untraceable. >> reporter: she's standing and looking at the jury, points to ferrante, "that man right there was one blood test away from the perfect murder." >> reporter: murder? responded the defense. what murder? robert ferrante, it said, did not commit a crime because there was no crime. >> i said as forcefully as i could, "we don't believe and we will never believe that autumn klein died from cyanide." >> reporter: the defense was attacking the cornerstone of the

commonwealth's case. that blood test with its reading of cyanide could never be trusted it said. >> reporter: there's no way that the result is reliable. throw it out. >> yes. >> reporter: because, the defense said, the lab initially screwed up with that 3.35 calculation, it only caught its error months later, correcting the level to 2.2, a still lethal amount of cyanide in autumn's blood. >> it certainly raises its a real issue of its credibility. >> reporter: and gives the defense something -- >> reporter: to work with? >> and absolutely gave the defense a lot to work with. >> reporter: far more reliable, argued ferrante's attorneys, was another test done in the weeks after autumn's death. it, too, found cyanide in her blood, but at very low levels nowhere near lethal. >> and in this case, that alone, as cyril wecht eloquently articulated, was more than reasonable doubt for this jury to acquit my client. >> reporter: dr. cyril wecht. the defense had introduced into the legal mix a renowned pittsburgh and internationally recognized pathologist of many years. dr. wecht had weighed in on cases from the jfk assassination

to the deaths of elvis presley and jon benet ramsey. he told the court the conflicting tests demanded a tie-breaker. >> what you do is you got to send it in again for laboratory testing. preferably to a third highly respected toxicology lab. that was not done. >> reporter: more compelling, he said, was evidence of scarring around autumn's heart, which could have triggered an electrical malfunction, stopping the organ cold. only on the spot cpr could have saved her. >> and in the absence of somebody hitting you in the chest, somebody knowing what they're doing with training in, in cardiopulmonary resuscitation, you probably will die. >> reporter: in other words, the defense said, autumn could have died of natural causes. they added that crime scene techs processed the house and never did find so much as a trace of the poison. and their client's cyanide google searches were done for research purposes, not murder.

i mean, here he is in january, asking questions of google about the nature of cyanide? >> right. >> reporter: this looks very bad. >> april, he's asking about cyanide, potassium cyanide, neuroscience. >> reporter: the defendant further explained his actions from the stand. he ordered the poison for work and even took it out of the box when it arrived. that's why his fingerprint was on the container. besides, his lawyer added, a man as smart as bob ferrante would never use a weapon that could so easily be traced back to him. >> that's like me buying a shotgun, telling everybody, "hey i just bought a shotgun," and two hours later my wife is deceased from a shotgun shot. >> reporter: couldn't be that stupid -- >> he would the dumbest guy in the universe. >> reporter: in closing the defense begged the jurors to use their common sense, which they later said is exactly what they did. their common sense and the science presented told them autumn klein had died of cyanide poisoning, because the defendant had given it to her. they found him guilty of first degree murder. >> crushing. crushing.

especially in this case. absolutely crushing. >> yep, good description. >> reporter: robert ferrante has since been sentenced to life in prison. he is challenging his conviction in court. for now, though, autumn's family feels they've gotten justice. their anger towards her husband has been overshadowed by all the what ifs. >> not only do i grieve autumn and the loss that she is to me and to us as a family and to our community and our friends, but also her patients. you know, my heart breaks for her patients. >> reporter: it was all dr. autumn klein had ever wanted to do, to help others. now, that chance is gone, swept aw that's all for now. i am lester holt. thanks for joining us. thquake in nepal leaves at least 2,000 dead.

we'll have the latest. also, the drone war. >> we all believed when we lose an american life. >> an american accidentally killed. is our drone war immoral or the only effective way to take out terrorists without endangering american lives. plus same sex marriage reaches the supreme court, again, and perhaps for the final time. i'll be joined by two former bush-gore foes who joined forces to fight for marriage equality. >> reporter: and hillary clinton's cash controversy. how damaging will these new stories be to her candidacy. finally, washington obsession with itself. >> feels ride to have a woman follow president obama doesn't it. my interview