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erin moriarty and i have been covering these trials. >> all right. thank you. >> reporter: there could be no sense of closure at the end of the sensational sexual assault trial of bill cosby. the judge declared a mistrial after the jurors reported they were hopelessly deadlocked on their sixth day of deliberations. >> whenever you have a case like this, where it's an in a sense a he said/she said situation, they're the only two witnesses there -- >> reporter: university of pennsylvania criminal law professor david rudowski. >> she gives a story. through cross-examination, though, the defense is able to show that she did certain things that might be inconsistent with what she said on the witness stand. those are the things that sometimes give jurors significant pause. >> reporter: jurors were unable to reach a unanimous vote in the case in which accuser andrew constand, a former temple university employee, claimed cosby, once known as america's tv dad, drugged and sexually assaulted her at his home in 2004. >> it's an old case. many years ago. raises

erin moriarty now on the savage murder of amy gellert. >> the gellert case is one that's kind of hauntedi think we have is really trying to figure out why it happened. >> reporter: on the evening of march 20, 1994, bunny and bob lehton returned from church to find a masked intruder in their cocoa beach, florida, home. >> basically, we had to crawl through here on our hands and knees, and he took us to this area right here. something switched in him. he just lost it, and he starts stabbing me in my neck, and it's going in so deep, i can feel the bones crunching. 21 reporter: miraculously, they both survived, but bunny's 21-year-old daughter, amy, who happened to come home during the attack, did not. amy's brother, ryan gellert: >> my first thought was i just couldn't believe it. it just didn't make sense. >> reporter: it's hard to think about her, isn't it? for the family, it's all the more painful because this more-than-20-year-old cold case has never been solved, but this cam of investigators in the brevard county sheriff's office is determined to catch the killer, or killers, who got a

erin moriarty of "48 hours" was in the massachusetts courtroom for the verdict. >>> there court havingiewed the evidence and applied the law thereto now finds you guilty. >> reporter: the defendant, 20-year-old michelle carter, lost her composure as judge lawrence monez announced his verdict in the death of her friend, conrad roy, who died in a kmart parking lot nearly three years ago from carbon monoxide poisoning. the judge found a stream of text messages and phone calls from carter persuaded 18-year-old roy to take his own life, even as he had doubts. >> this court finds that instructing mr. roy to get back in the truck constitutedconstit and reckless conduct. >> reporter: in the last week of roy's life, carter sent dozens of texts urging him to call himself, all part of what prosecutors say was an attempt to gain sympathy and attention from classmates. "you're ready and prepared. all you have to do is turn the generator on and be free and happy." but it was this text from carter to her friend sent two months after roy's death that sealed her fate. "i could have stopped him. i was o

many messages encouraged him to kill hirs. ""48 hours'"" erin moriarty is at the courthouse right nowod morning, erin. >> reporter: good morning, gayle. they're still trying to make sense why he didn't talk to them about his suicide plans but turned to someone else. the person he did reach out to woman he befriended on a florida vacation. both teenagers were struggling emotionally. michelle suffered from an eating disorder while conrad had previously tried to take his own life. he spoke about his depression in this video he made. >> i'm 18 years old and i still haven't recovered from social anxiety, depression. it's confounding me. >> they bonded over text messages. he confided he had suicidal thoughts and many the weeks before his death, michelle's responses were disturbing. i thought you really wanted to die, but apparently you don't. i feel played and just stupid. and then eight days later conrad got into his truck. you can't think about it. you just have to do it. he died from carbon monoxide poisoning after purposely breathing in prosecutors indicted michelle carter for involunta

she is a hours" erin moriarty is outside the courthouse in taunton, massachusetts, where the trial isis morning. >> reporter: good morning. they have to prove the defendant's action were wanton and reckless enough to cause her friend's suicide. although, keep in mind she was 35 miles away. the real question is was her virtual presence powerful enough, rea enough to push conrad roy into taking his own life. >> she put him in that car that night. she listened to him as he died. >> reporter: prosecutors say michelle was on the phone with conrad roy while he was taking his own life but never alerted the police. they accused the then 17-year-old from manipulating her friend who was dealing with depression. >> from july 6th through july 12th, she asked conrad 40 times when was he going to kill himself. >> reporter: in one text she told him to inhale knox shus car exhaust. she said you don't feel pain. roy seemed to have second thoughts and said why am i so hesitant lately. carter respond you keep overthinking it and keep pushing it off. you just need do it, conrad. roy's body was found in h

conrad roy with texts and urged him to take his life because she wanted attention. "48 hours" erin moriartye trial. good morning. >> good morning. prosecutor introduced video into evidence. they showed conrad roy speaking candidly about his inner turmoil, but that's something that could also help the defense. michelle carter's attorneys argue he was already suicidal long before he met her. >> this is conrad henry roy iii reporting about social anxiety. >> reporter: at times conrad roy seemed brimming with hope from his videos. >> i just got a job to captain their boat. that's a huge accomplishment. >> reporter: but later his despair came into focus. >> it's no good. trash. will never be successful. i' i'd have a wife, never have kids, never learn. >> reporter: in july to 14 roy died inside his truck from carbon monoxide poisoning. as he was dying, prosecutors say he was on phone with michelle carter for 46 minutes. days before numerous texts, carter, then 17, offered roy suggestions on-on-how to take his own life and lex tured him when he wavered. i'm tired of you not taking it seriously. i