Pennsylvania's highest court has overturned Bill Cosby’s sexual assault conviction.

AP has reported that the decision was reached after finding an agreement with a previous prosecutor that prevented Cosby (pictured) from being charged in the case.

Cosby has served more than two years of a three-to 10-year sentence at a state prison near Philadelphia, the AP added.

He had vowed to serve all 10 years rather than acknowledge any remorse over the 2004 encounter with accuser Andrea Constand.

The Pennsylvania Parole Board in May turned down Cosby's petition to be released from the 10-year prison sentence for aggravated indecent assault, citing his refusal to participate in a therapy programme for sexually violent predators.

Laura Treaster, a spokeswoman for the state parole board, confirmed the decision, which was made on May 11 and first reported by Nicole Weisensee Egan, author of the book "Chasing Cosby," on her Facebook page.

Cosby spokesman Andrew Wyatt said his client expected to be turned down. “We knew he was going to be rejected. He called me and told me that if he didn’t take the course, he would be denied," He has maintained his innocence from the beginning.”

Cosby, now 83, would have become eligible for parole on September 25 after completing the three-year minimum term of his sentence. He was designated a sexually violent predator on September 25, 2018, after being convicted earlier in the year for the rape of Constand, his former friend at Temple University, in 2004.

The once-beloved comedian known as “America’s Dad” has been serving his sentence in the State Correctional Institution at Phoenix, a suburb in Philadelphia.

Treaster said the board would not consider Cosby for parole again unless he completes the sexually violent predator therapy. He must have also overcome a recommendation against parole from the state Department of Corrections and maintained a clear conduct record. Cosby was also told to develop “parole release plan.”

She said the reasons for the negative recommendation by the Corrections Department, and Cosby’s prison conduct record, are not public information.

Cosby had a hearing before the Pennsylvania Supreme Court in December on his appeal of his conviction. 

Wyatt at the time said Cosby was doing as well in prison as can be expected.

“He’s hopeful,” Wyatt said of the Supreme Court appeal. “He’s cool as a cucumber."