Cosby's legal team seek to halt trial by claiming comic was granted immunity
The criminal sexual assault case against Bill Cosby may be in jeopardy after his defence said the prosecutor who examined the same claim in 2005 gave his word that the comedian would not be charged.
Mr Cosby's lawyers have asked for the aggravated sexual assault charges to be dismissed, contending that they "violate an express agreement" with the district attorney at the time, which they say constitutes an immunity deal.
The comedian was charged in December with drugging and sexually assaulting Andrea Constand, then a basketball player with Temple University, at his home in 2004, in a case that could see the 78-year-old face up to 10 years in jail.
Ms Constand first brought the charges against Mr Cosby in a 2005 civil law suit, which was presided over by Bruce Castor in Pennsylvania.
No criminal charges were brought and Mr Cosby settled for an undisclosed sum.
The deposition in Ms Constand's 2005 suit has been cited by prosecutors as the impetus for reopening the case in a criminal court.
In it, Mr Cosby admitted giving her wine and sedative pills before performing a sexual act, but said the sex was consensual. He also admitted to using Quaaludes (a sedative) as a seduction tool in the 1970s and to paying off other women to keep them quiet.
Mr Castor, who has been called by Mr Cosby's legal team as a defence witness, said he had guaranteed the comedian that the deposition would not result in criminal charges.
He made the immunity deal in a "verbal agreement" with Mr Cosby to encourage him to speak and thereby help the civil suit against him, he said.
But Kevin Steele, the current district attorney, said there was no evidence of a signed immunity agreement through traditional, agreed channels.
Dolores Troiani, an attorney for Ms Constand in 2005, told CNN on Friday she had never been told of such an agreement.
The network reported that Mr Castor wrote an email to his successor last year, warning that the deposition could not be used.
"I can see no possibility that Cosby's deposition could be used in a state criminal case," he said, explaining that he would have to testify about his promise.
"Unless you can make out a case without that deposition and without anything the deposition led you to, I think Cosby would have an action against the county and maybe even against you personally."
Last week, Mr Cosby's lawyers filed a motion asking for the charges against the comedian to be dismissed on the grounds that they were brought "illegally improperly and unethically" by Mr Steele, the district attorney and his office because they "violate an express agreement made" by the county in 2005.
The trial judge will consider the motion on February 2.
Mr Cosby has steadfastly denied wrongdoing in this case and the dozens of other allegations. As many as 49 other women have accused him of sexual assault in allegations that date back to the 1970s, though none ever resulted in a charge in a court of law.