The trial of US comedian and actor Bill Cosby for sexual assault has begun in Pennsylvania.
Former university employee Andrea Constand alleges he drugged and molested her in 2004.
Mr Cosby, 79, says he is innocent and the encounter was consensual. The trial is expected to last about two weeks.
It is being seen as the biggest US celebrity court case since the murder trial of former American football player OJ Simpson in 1995.
Several of Mr Cosby’s co-stars from the 1984-1992 sitcom The Cosby Show are expected to attend the trial in Norristown, outside Philadelphia. One of them, Keshia Knight Pulliam who played his daughter on TV, accompanied him into court.
His wife of 53 years was not seen with him as he entered the suburban courthouse.
More than 100 journalists are expected to cover the trial.
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Christine Cornell
Cosby sat at the front of the court throughout the opening proceedings
In the courtroom: BBC’s Courtney Subramanian
The courthouse, in Norristown, about 20 miles (32km) outside Mr Cosby’s home city of Philadelphia, swarmed with reporters as the celebrity arrived, emerging slowly from the back seat of a black SUV.
Inside court he reappeared, dressed in a navy suit and a striped tie, never turning towards the packed courtroom behind him.
He sat stoically, facing forward and periodically leaning over to confer with one of his lawyers. At one point he spoke out to no-one in particular, as one of his associates had walked away, perhaps revealing his issues with poor sight. But as members of the jury entered, Mr Cosby – like everyone else in the room – turned his attention to their corner.
Judge Steven O’Neill appealed to the courtroom full of reporters to “let the trial play out”, before spending the first hour explaining to jurors their job.
What is Cosby accused of?
Mr Cosby faces three counts of aggravated indecent assault. Each count carries a maximum sentence of 10 years and a fine of up to $25,000 (£19,500).
In 2004 Ms Constand was 31 when she visited Mr Cosby’s home seeking career advice after befriending him through Temple University in Philadelphia, where he served on the board of trustees.
She said Mr Cosby gave her three blue pills which made her legs feel “like jelly” and that he then began to touch her inappropriately.
Mr Cosby’s defence lawyers argued on Monday that the pair had multiple romantic encounters, and that Mr Cosby only offered her drugs after she complained of trouble sleeping.
In 2006, the comedian settled with Ms Constand after providing an undisclosed cash sum to her.
At least 50 women have accused Mr Cosby of sexual assault, but he only faces charges in Ms Constand’s case because of statutes of limitations.
What is the evidence against him?
Prosecutor Kristen Feden called upon jurors to look beyond his role as Dr Cliff Huxtable.
That the wholesome TV image “will be shattered”, she said, accusing Mr Cosby of “heinous crimes”.
By drugging women and making them legally unable to consent to sex, Mr Cosby put them in a position “so that they couldn’t say no”, Mrs Feden told jurors.
She also frequently referred to Mr Cosby’s own admission in 2005 that he had used drugs as part of his efforts to have sex with women.
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Reuters
Ms Constand says she was drugged and assaulted
The drugs, called Quaaludes, are a sedative that was widely used recreationally in the US in the 1970s.
However Judge Steven O’Neill has ruled that the court will not hear about the 2006 civil case. Neither will jurors hear from Mr Cosby’s many other accusers.
What is Mr Cosby’s defence?
Mr Cosby says his encounter with Ms Constand was consensual, and his lawyer pointed to evenings spent sipping cognac at his home as proof of their friendship.
He also says he offered women drugs as a way to encourage them to relax rather than a way to render them helpless.
On the night of the alleged sex assault, Mr Cosby says he gave Ms Constand some Benadryl, an anti-allergy medication that can cause drowsiness, because she appeared stressed.
Mr Cosby’s lawyers asked on Monday why Ms Constand returned to Mr Cosby’s house after she said he had made previous unwanted sexual advances on her.
They also presented evidence that the two had more than 70 phone discussions after the alleged incident, and accused Ms Constand of changing her story to police at least three time.
They also questioned why the case is being brought now, more than 10 years after a previous district attorney decided there was not enough evidence to go to trial.
Will he testify?
No – Mr Cosby has said he will not testify and last month told Sirius-XM radio that he feared prosecution lawyers could twist his words on the stand.
“When you have to deal with examination, cross-examination, et cetera, et cetera, more than two sides to every story – sometimes it’s four or five,” he said.
He has also speculated that some of the allegations against him could be motivated by racism.
Who is on the jury?
The jury is made up of seven men and five women. They include two black people and 10 white people, the New York Times reported.
The jurors are from the Pittsburgh area, 300 miles to the west of the court in Norristown, because Mr Cosby’s defence team argued that jurors there could have been affected by pre-trial publicity.
The jurors will be kept away from media reports for the duration of the trial.
Why is Bill Cosby important?
Mr Cosby is best known for his role as the father in the television hit The Cosby Show, which was a huge hit in the US and around the globe.
At one point he was the highest-paid actor in the US.
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United Archives / Alamy
At its peak, some Cosby Show episodes were watched by half of all US TV viewers
He was born in Philadelphia and started his career as a stand-up comedian in 1962, debuting on NBC’s The Tonight Show in 1963.
In 1965, he became the first black actor to star in a drama series in the US, in the espionage show I Spy. He earned three consecutive best actor Emmys for his role, at a time of high race tensions in the US.
In 2013 he did a national stand-up tour and received rave reviews. After that, several women began to come forward with allegations of sexual assault, some going back nearly 30 years.
Bill Cosby’s trial for sexual assault begins in Pennsylvania