Bill Cosby was charged Wednesday with drugging and sexually assaulting a woman at his home 12 years ago – the first criminal charges brought against the comedian out of the torrent of allegations that destroyed his good-guy image as America’s Dad.

The case sets the stage for perhaps the biggest Hollywood celebrity trial of the mobile-all-the-time era and could send the 78-year-old Cosby to prison in the twilight of his life and barrier-breaking career.

Prosecutors accused him of plying former Temple University employee Andrea Constand with pills and wine, then penetrating her with his fingers without her consent, while she was drifting in and out of consciousness, unable to resist or cry out.

She was “frozen, paralysed, unable to move,” Montgomery County District Attorney-elect Kevin Steele said. In court papers, prosecutors said the drugs were the cold medicine Benadryl or some other, unidentified substance. Steele noted that Cosby has admitted giving quaaludes to women he wanted to have sex with.

The TV star acknowledged under oath a decade ago that he had sexual contact with Constand but said it was consensual. Calls to his attorneys were not immediately returned.

He was to be arraigned in the afternoon on a charge of aggravated indecent assault, punishable by five to 10 years behind bars and a $25,000 fine.

The charges came down just days before the 12-year statute of limitations for bringing charges was set to run out.

The case represents an about-face by the district attorney’s office, which under a previous DA declined to charge Cosby in 2005 when Constand first told police that the comic violated her by putting his hands down her pants at his home in the Philadelphia suburb of Cheltenham.

Prosecutors reopened the case over the summer as damaging testimony was unsealed in Constand’s related civil lawsuit against Cosby and as dozens of other women came forward with similar accusations that made a mockery of his image as the wise and understanding Dr. Cliff Huxtable from TV’s “The Cosby Show.”

At that point, “reopening this case was not a question. Rather, reopening this case was our duty as law enforcement officers,” Steele said.

He urged any other alleged victims to come forward as well.

Constand, who is now 42, lives in Toronto and works as a massage therapist. Her attorney, Dolores Troiani, welcomed the charges.

“She feels that they believe her, and, to any victim, that is foremost in your mind: Are people going to believe me,” Troiani said.

The case adds to the towering list of legal problems facing the TV star, including defamation and sex-abuse lawsuits filed in Boston, Los Angeles and Pennsylvania. But as for criminal charges, many of the alleged assaults date back decades, and the statute of limitations has expired in nearly every case.

Cosby in 1965 became the first black actor to land a leading role in a network drama, “I Spy,” and he went on to earn three straight Emmys. Over the next three decades, the Philadelphia-born comic created TV’s animated “Fat Albert” and the top-rated “Cosby Show,” the 1980s sitcom celebrated as groundbreaking television for its depiction of a warm and loving black family headed by two professionals – one a lawyer, the other a doctor.

He was a fatherly figure off camera as well, serving as a public moralist and public scold, urging young people to pull up their saggy pants and start acting responsibly.

Constand, who worked for the women’s basketball team at Temple, where Cosby was a trustee and proud alumnus, said she was assaulted after going to his home in January 2004 for some career advice.

Then-District Attorney Bruce Castor declined to charge Cosby, saying at the time that the comedian and his accuser could be portrayed in “a less than flattering light.” This year, Castor said that if the damning allegations in Constand’s lawsuit had been known at the time, “we might have been able to make a case.”

Castor tried to make a comeback as district attorney in the November election but lost.

After the criminal case went nowhere, Constand settled her lawsuit against Cosby in 2006 on confidential terms.

Her allegations and similar ones from other women in the years that followed did not receive wide attention at the time but exploded into view in late 2014, first online, then in the wider media, after comedian Hannibal Buress mocked the moralising Cosby as a hypocrite and called him a rapist during a standup routine. (AP)

•Photo shows Bill Cosby.