The prosecution claims that Cosby drugged his accuser, leaving her paralysed. Cosby's lawyers say there are numerous inconstancies in her case and ask why a violated woman would make 72 calls to her alleged attacker after the assault.
The first witness to testify in Bill Cosby's sexual assault trial said on Monday that the comedian had drugged her before sexually abusing her in 1998 - the same method prosecutors say he used in the alleged 2004 attack that he is on trial for.
Cosby, once one of the most beloved entertainers in the United States, is accused in both instances of inviting a young woman to visit him for career advice, offering her pills that he said would help her "relax" and then sexually abusing her once she was incapacitated by the drug.
The 79-year-old entertainer is charged with sexually assaulting Andrea Constand, an employee of his alma mater Temple University, at his home in the Philadelphia suburbs in 2004.
Constand is one of dozens of women who have accused Cosby of sex assault but hers is the only case recent enough to be subject to criminal prosecution. The allegations, all of which Cosby has denied, have essentially ended his long career.
The first witness at his trial, Kelly Johnson, described an incident that she said took place at Cosby's hotel suite in Los Angeles in 1996. Her emotional testimony was intended to persuade jurors that Cosby demonstrated a pattern of behavior when he allegedly attacked Constand in 2004.
A tearful Johnson, who worked at the time for Cosby's agent, said she initially hid the pill under her tongue but that Cosby checked to see if she had swallowed it. She later woke up disoriented and partially clothed in Cosby's bed with the comedian behind her, grunting, before he forced her to touch his genitals, she testified.
"I was trying to say something," she said. "I don't know if I was actually speaking."
Constand filed a police complaint in 2005 over the encounter at his home. The district attorney at the time said the case was too weak to prosecute. But a new set of prosecutors charged Cosby a year and a half ago after the deposition became public and numerous women came forward.
Talked 72 times
Defense lawyer Brian McMonagle immediately attacked what he said were inconsistencies in Constand's story, disputed that Constand was incapacitated, and made the case that she and Cosby, who was married, had a romantic relationship. McMonagle said Cosby gave her the cold and allergy medicine Benadryl only after she complained she couldn't sleep.
McMonagle said Constand changed the date of the encounter from mid-March to mid-January of 2004. And he said Constand initially told police that she and Cosby had never spoken afterward, when, in fact, phone records show the two talked 72 times after mid-January — and two-thirds of the calls were initiated by Constand.
On Monday, McMonagle suggested Constand and the other accuser set to testify were seeking payouts over the allegations. And he told jurors that Cosby apologized to Constand's mother in a phone call the year after the encounter not because he had assaulted her, but to say, "I'm sorry, I'm a married man, and I never should have done it."
Cosby's lawyers tried repeatedly to get the case thrown out. They said Cosby testified in the lawsuit only after being promised he could never be charged. And they argued that the delayed prosecution makes the case impossible to defend, given that witnesses have died, memories have faded and Cosby, they say, is blind.
People who say they are sexual assault victims are not usually identified unless they grant permission, which Constand has done. The case is continuing.
Cosby is charged with three counts of aggravated indecent assault. He could get 10 years in prison if convicted.
Cosby's wife, Camille, was absent as the TV star, carrying a wooden cane and grabbing his spokesman's arm for support, walked past dozens of cameras into the courthouse. He chatted with actress Keshia Knight Pulliam, who played his daughter Rudy on the top-rated "Cosby Show," as they walked.
Cosby smiled but said nothing when someone asked how he was feeling. Pulliam told reporters she came to the trial to support her TV dad.
"I want to be the person that I would like to have if the tables were turned," she said. "Right now it's the jury's job and the jury's decision to determine guilt or innocence. It's not mine or anyone else's."
Cosby built a good-guy reputation as a father and family man, on screen and off, during his extraordinary 50-year career in entertainment. He created TV characters, most notably Dr. Cliff Huxtable, with crossover appeal among blacks and whites alike. His TV shows, movies and comedy tours earned him an estimated $400 million.
Then a deposition unsealed in 2015 in a lawsuit brought by Constand revealed that Cosby had a long history of extramarital liaisons with young women and that he obtained Quaaludes (Methaqualone) in the 1970s to give to women before sex. Dozens of women soon came forward to say he had drugged and assaulted them.
The statute of limitations for prosecuting Cosby had run out in nearly every case. This is the only one to result in criminal charges against the comic.
"Power and fame"
In her opening statement at the start of the famed comedian's trial on Monday, Assistant District Attorney Kristen Feden said Bill Cosby used his power and fame to sexually assault an employee of Temple University's basketball programme.
Feden told jurors that celebrities like Cosby are seen as "larger than life."
"We think we really know them," she said. "In reality, we only have a glimpse of who they really are."
Prosecutors had wanted to call as many as 13 of Cosby's more than 60 accusers as witnesses, but Montgomery County Judge Steven O'Neill ruled that only Constand and the other woman could take the stand.
Celebrity attorney Gloria Allred, who showed up for the first day of the trial, told reporters she is hopeful "there will be justice in this case."
Allred represents several of Cosby's accusers, including the one who will testify for the prosecution — a woman who worked for the comedian's agent at the William Morris agency.
"I'm not going to predict what the outcome is," Allred said. "We'll see what the evidence is. But this case is not going to be decided on optics, it's going to be decided on the evidence, and finally, it's Mr. Cosby who's going to have to face that evidence and confront the accusers who are against him."