But the state’s top court has now ruled that the current District Attorney should have stood by his predecessor’s decision to not charge Mr Cosby, who went on to make allegedly incriminating statements at a later civil lawsuit deposition.
His trial was told that Ms Constand had known Mr Cosby for two years when in 2004 he invited her to his mansion outside Philadelphia for career advice.
Ms Constand, then 29, had met Mr Cosby, in 2002 when she was the director of operations for the women’s basketball team at Temple University, where the star ran track and field and played football in the 1960s.
Mr Cosby testified in his 2005 civil suit deposition that he had “a romantic interest” in Ms Constand, who is gay and had a girlfriend at the time of the incident.
Over the next 14 months Mr Cosby, who is 35 years older than Ms Constand, stayed in touch with her by “inviting her to my house, talking to her about personal situations dealing with her life, growth, education, access and thoughts to how to acquire a more aggressive attitude, protecting oneself in business,” he stated in his deposition.
Ms Constand said that Mr Cosby had invited her to his Pennsylvania estate in January 2004 to discuss her career plan.
According to a probable cause affidavit, Mr Cosby says that he had made three prior romantic advances towards Ms Constand, which he said she had not rebuffed, while she said that she rejected them.
On the evening of the alleged incident, Mr Cosby admitted that he had given Ms Constand some Benadryl to help her relax.
She said that Mr Cosby had told her it was a herbal medication and that it left her unable to speak or move as he was “fondling her breasts, put his hand in her pants … penetrated her vagina with his fingers” and “took her right hand and placed it on his penis”, the arrest affidavit stated.
Ms Constand told investigators that she had “no interest whatsoever” in a romantic relationship with Mr Cosby, but that they had a “sincere friendship” and she viewed him as a “mentor”.
Almost exactly one year after the alleged incident, Ms Constand went to the police and filed a criminal report.
But in February 2005, then Montgomery County District Attorney Bruce Castor, who defended Donald Trump at his second impeachment trial earlier this year, decided not to bring charges against Mr Cosby, citing “insufficient credible and admissible evidence”.
Ms Constand then filed a civil lawsuit against Mr Cosby, following which 13 other women came forward to make similar claims against him.
The civil lawsuit was settled out of court by Mr Cosby for more than $3m in November 2006, and the testimony it created was kept under seal until 2015, when a federal judge unsealed it as part of a defamation suit filed by seven women who claimed Mr Cosby drugged and sexually assaulted them.
The investigation into Ms Constand’s criminal case was then re-opened because during his deposition Mr Cosby admitted buying Quaaludes, a sedative pill, to have sex with women.
Mr Cosby has claimed that his encounter with Ms Constand was consensual, and was denied parole earlier this year for refusing to take part in sex offender programmes in state prison. He had said he would rather serve the maximum 10 year prison sentence than acknowledge wrongdoing.
One of the women who has claimed she was attacked by Mr Cosby reacted angrily to the decision to overturn his conviction.
Beth Ferrier, 63, has alleged that Mr Cosby attacked her in 1984, and called his release “bulls**t.”
“It’s money and power. He’s so guilty of what he did. It doesn’t matter, and it sets a precedent,” she said in the phone call. “It’s not okay,” she told The New York Post.
“Is it because of power and money that he gets to do this? I’m floored by it. He’s guilty. We got him in prison.”