Transcript for From 'America's dad' to sexual assault allegations: Bill Cosby's fall from grace
It is 1984. And the very first episode of "The Cosby show" is premiering. Let's put on some music around here. ?????? Reporter: It is the show that would catapult its star and creator Bill Cosby into America's collective consciousness, branding him one of the most famous and beloved TV dads. We knew him for his comedy. ?????? Reporter: His shows. Hey, hey, hey, it's fat Albert! Reporter: And the Jell-O. You know how the kids love Jell-O pudding. He was an enormously admired man. It seems there was so much about him we really didn't know. Reporter: Heidi Thomas knew a different man. In 1984, the same year the show launched, she alleges Bill Cosby sexually assaulted her. My name is Heidi Thomas. I was 24 years old when I first met Bill Cosby. Reporter: As seen in A&E's documentary "Cosby: The women speak," Thomas alleges Cosby drugged her when she was invited to Reno for acting coaching. He said, let's try a cold read. So he handed me a script. And the person I'm supposed to be clearly is intoxicated. I do remember him saying, Heidi, have you ever been drunk? And I said, no, not really. And he said, well, how do you expect to play a role like this? So he poured a glass and he said, all right, this is your prop. You're going to sip on your wine. And I literally -- I don't remember anything other than one sip. Reporter: She says the next four days are a drug-induced blur. But she says she does remember mental snapshots. My clothes were on, his were not. And I was lying down. And he was forcing himself in my mouth. Then the next snapshot is I hear his voice basically telling me that we're going to be doing this again. And I thought, this isn't why I'm here. Reporter: Cosby has denied any nonconsensual relations. She waited until three years ago to tell her story publicly in detail. I knew that if I made this allegation against the squeaky-clean Bill Cosby, who's she going to believe? In the battle of public opinion alone, he was teflon. What's Bobo's temperature? Zero. Reporter: Because of his adoring public he was not only a guest in their homes, he was already a cultural trail blazer. Hello, sir. Reporter: In 1965, Cosby broke through as the first black actor to star in a lead role in a network show "I spy." And in the 1980s, the eponymous "Cosby show" streaming into over 20,000 households each Thursday night, the most-watched show of the decade. He made people, especially in the African-American community, feel that the depiction of a dad who was a doctor, who was married to a wife who was very accomplished and who he loved, depicted something about themselves. They were the huxtables. Reporter: Post-cosby show, he transitioned from everyone's favorite father to perhaps everyone's crotchty grandfather, especially in the black community. Everybody knows it's important to speak English, except these knuckleheads. He was sharply critical with the way some people were bringing up their children. Sharply critical the way some young people were behaving. Reporter: Before he cleaned up his image, there have been signs of a darker side to Cosby, at least in his comedy routines. You know anything about Spanish fly? Reporter: One of his more popular gags he started in the '60s, a joke about giving a woman an afro Dees I am. There's this girl, crazy Mary, he put should in her drink, man. Reporter: In 2015, to the 13 women sitting down for that A&E documentary "Cosby: The women speak," there's nothing funny about Cosby's alleged behavior. He put a pill next to my wine glass "Here, take this, this will make you feel better," Victoria and other accusers offer shockingly similar accounts of coercion throughout the height of Cosby's fame. He said, no, no, you need to drink it to loosen up. He said, just relax, have a drink first. Reporter: Alleged acts of sexual assault. And then all of a sudden I realized everything was very, very silent. So I opened my eyes and looked around. And he came over to me and at that point extracted his pound of flesh. If there is any question about why women don't report rape is because it's so damned humiliating. You don't want to ever talk about it again. Reporter: I sat down with Cosby in 2015. Good to see you. Reporter: As he promoted a nonprofit organization. He was defiant in the face of the women's claims and the effect they may have on his legacy. Are you concerned at all that given the allegations, that that may overshadow your message? It's interesting. This is a situation that's unprecedented. My family, my friends, I have been in this business 52 years. And I will -- I've never seen anything like this. And reality is -- the situation. And I can't speak. A young person comes up to you and says, my mom says you've done some bad things. How will you answer them? If they are pressing you, are you guilty, did you do it, are the allegations true? I am prepared to tell this young person the truth about life. I'm not sure that they will come like that. I think that many of them say, well, you're a hypocrite. Reporter: But two months bombshell civil deposition was released. In it, the description of a 2004 encounter between Cosby and Andrea constand, Cosby's own words creating the first real cracks in his public image. Cosby's legacy at one point bolstered by the women's silence. Today it has been shattered by all of their voices. Justice has been done. It has to start with people stepping up and speaking out. You have to speak your truth. You have to go to the police. You must get a rape kit. You must do it. Because they won't be held accountable. Reporter: The judge now has up to 90 days to decide Cosby's fate. But whether Cosby spends the rest of his life in jail or not, for the women who have waited so long for this day, they say they've already been set free. But today, this jury has shown that the "Me too" movement, what the "Me too" movement is saying, that the
This transcript has been automatically generated and may not be 100% accurate.