In one of America's biggest celebrity trials in years, the 79-year-old pioneering black comedian faces three counts of aggravated indecent assault, which each carry a maximum sentence of 10 years in jail and a $25,000 fine.
Around 60 women have publicly accused the Emmy-winning television star and comedian of being a serial sexual predator in remarkably similar accusations that span four decades, ending his career and shredding his reputation.
But his fate rests on the allegations of just one, 44-year-old Canadian massage therapist Andrea Constand, who alleges that he drugged and sexually assaulted her at his Philadelphia mansion in January 2004.
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On Wednesday, Constand's mother, Gianna, told the third day of trial in Norristown, Pennsylvania that she and her daughter spoke to Cosby for more than two hours by telephone about a year after the alleged assault.
"I wish I had recorded it," she testified. During the conversation, Cosby admitted to giving her daughter pills and touching her private parts, but was "trying to lead me to believe that it was consensual," Constand's mother said.
She accused the actor of having tried to "manipulate" her and offering to pay for Andrea to go to therapy. "I got very aggressive. I was very rude. I wanted to know what he gave her," she said.
"She viewed him as a father," she added. "He betrayed her."
"The only thing I'd like from you is an apology," she said she told him during their conversation.
'Changed your story'
"I apologize to Andrea and I apologize to you mommy," she quoted Cosby as having said in reply. "He admitted that he was a sick man." After an hour on the stand, Constand broke down in tears, burying her head in her hands.
Cosby, one of the towering figures of US popular culture in the second half of the 20th century, was once adored by millions as "America's Dad" for his seminal role as a lovable father and obstetrician on hit TV series "The Cosby Show."
The defense grilled Andrea Constand earlier on Wednesday for nearly five hours, focusing on inconsistencies in her past testimony, on which much of the case rests in what experts say will boil down to her word against his.
THE COSBY SHOW -- "Off to See the Wretched" Episode 23 -- Air Date 04/05/1990 (Photo by NBC/NBCU Photo Bank via Getty Images) (NBC) Source: Getty Images
Constand says she went to his home to seek career advice after coming to regard the pioneering black comedian, movie actor and television star as a mentor.
Cosby says that he gave Constand the antihistamine Benadryl only to relieve stress, insisting that their sexual relations were consensual and accusing her of lying.
Defense lawyer Angela Agrusa zeroed in on statements Constand gave to police in early 2005.
She originally said the alleged assault took place on March 16, 2004 and initially failed to disclose other meetings with Cosby.
"You changed your story," Agrusa told Constand in the Montgomery County Court as Cosby sat in court, averting his gaze from his accuser.
During breaks, the defendant -- who maintains he is legally blind -- appeared upbeat and exchanged pleasantries with the aide accompanying him.
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'Bath Salts?'
Just weeks after the alleged assault, Constand joined Cosby at a dinner with other guests and gave him a present on behalf of one of her friends.
"You're coming to the man that assaulted you and you're bringing him bath salts?" Agrusa asked.
Constand kept her cool, correcting statements she thought inaccurate, speaking firmly, often looking at the 12 jurors directly and smiling regularly.
"Mr Cosby never disclosed to me that he was interested in a romantic interaction with me," said Constand, dressed in a white jacket and a light blue top.
After the defense had finished, assistant district attorney Kristen Feden counter-attacked, hammering home certain key points.
Asking Constand to read passages from her evidence in 2005, she emphasized that if she made various mistakes and omissions here and there, her detailed account of the alleged assault itself had not changed.
"You did not consent," Feden said three times, to which Constand replied in the affirmative each time.
Thirty years old at the time, Constand was director of women's basketball at Temple University, where Cosby sat on the board of trustees.
