Bill Cosby’s sentencing hearing has opened with a debate over whether the 81-year-old comedian should be branded a “sexually violent predator”.

Such a designation would make him subject to mandatory lifetime counselling and community notification of his whereabouts.

Cosby, who faces up to 30 years in prison for drugging and molesting a Temple University women’s basketball administrator in 2004, fought the prosecution’s effort to classify him as a predator under state law.

Kristen Dudley, a Pennsylvania state board psychologist, said that Cosby has an uncontrollable urge to violate young women and would probably commit another offence if given the chance.

Ms Dudley added that Cosby’s assault of Andrea Constand fits a long pattern of predatory behaviour by the former Cosby Show star.

Andrea Constand arrives at Bill Cosby's sentencing hearing
Andrea Constand arrives at the sentencing hearing (David Maialetti/The Philadelphia Inquirer via AP)

Cosby often befriended women, then betrayed their trust by sedating them with drugs or alcohol and violating them for the “sole purpose of his sexual gratification”, Ms Dudley said.

Trying to avoid the predator designation for their client, Cosby’s lawyers argued that the state law itself is unconstitutional.

Politicians in Pennsylvania and elsewhere have repeatedly rewritten their sex offender reporting laws after courts found them vague and unfairly punitive.

Prosecutors told Judge Steven O’Neill the law is necessary for public safety, and the judge allowed the hearing on Cosby’s status to proceed.

The legal wrangling came at the start of a hearing that will determine how the comedian will be punished for knocking Ms Constand out with pills and assaulting her at his suburban Philadelphia home more than 14 years ago.

Cosby was the first celebrity to go on trial in the MeToo era and could be the first to go to prison – perhaps for the rest of his life – after being convicted in April.

He walked into the courthouse on the arm of his longtime spokesman as protesters shouted at him.

Ms Constand arrived a short time later.

At the end of a hearing that could last two days, the judge could sentence Cosby to as much as 30 years in prison or send him home on probation.

Bill Cosby arrives at Montgomery County Courthouse
Cosby arrives at Montgomery County Courthouse (Matt Slocum/AP)

The state guidelines for someone like Cosby, with no prior convictions, call for about one to four years behind bars.

Cosby is legally blind and uses a cane, something his lawyers are certain to point out along with his achievements and philanthropy.

In the years since Ms Constand first went to police in 2005, more than 60 women have accused Cosby of sexual misconduct, though none of those claims have led to criminal charges.

Two of those women, Lise-Lotte Lublin and Chelan Lasha, said they want prison for him and hope they get to make impact statements at the sentencing.

“I really think it’s important that he spend some time behind bars,” said Ms Lublin, who alleges Cosby assaulted her in 1989 when she was 23.

“At some point, he should acknowledge what he’s done, and do the time for the crime.”

Ms Lublin and former model Janice Dickinson – another Cosby accuser – were among those in the courtroom.

Janice Dickinson arrives at the sentencing hearing
Janice Dickinson arrives at the hearing (David Maialetti/The Philadelphia Inquirer via AP)

Prosecutors had hoped to have some of the other accusers address the court at sentencing to paint Cosby as a serial sexual predator deserving of prison.

But the district attorney’s office said they would not be taking the stand.

It remained unclear whether Ms Constand herself would speak at the sentencing.

Just a few hours before the hearing began, she tweeted a Bible verse about letting go of anger: “Be wrathful, but do not sin; do not let the sun set while you are still angry; do not give the Devil an opportunity.”

Cosby, who grew up in public housing in Philadelphia, became the first black actor to star in a prime-time TV show, I Spy, in 1965.

He remained a Hollywood A-lister for much of the next half-century, hitting his peak in the 1980s with the top-rated Cosby Show as the warm, wisecracking father Dr Cliff Huxtable.