LOS ANGELES (AFP) - Bill Cosby sexually assaulted a teenager at the Playboy Mansion almost 50 years ago, a jury in California found Tuesday, in the first civil ruling against the veteran entertainer following dozens of allegations.

Judy Huth, now aged 64, was awarded $500,000 in damages after the jury in Santa Monica determined that Cosby had molested her in 1975 when she was just 16 years old after meeting her on a movie set and plying her with alcohol.

The case is the only successful legal action against Cosby, 84, who has been accused of using his fame to prey on women over several decades.

The man formerly known as "America's Dad" was jailed in Pennsylvania for drugging and molesting a woman in a separate criminal case in 2018, but was freed last year when his conviction was overturned on a technicality.

Over a two-week civil hearing, which Cosby did not attend, lawyers said he escorted Huth and her then-17-year-old friend, Donna Samuelson, to Hugh Hefner's mansion after meeting them on a movie set.

The jury heard how when Huth was alone with Cosby, the actor began kissing her and tried to put his hands inside her clothes.

They were told how he then allegedly pulled down his own trousers and forced her to perform a sex act on him.

Lawyer Nathan Goldberg said for many years Huth had repressed memories of the assault but that it came to the fore for her when other women began accusing him of assaulting them.

- Much-loved star -
"It was like a cork popped out of a bottle," said Goldberg at the start of the case. "Memories came rushing to the surface... she became overwhelmed by memories of Mr Cosby and what he had done."

She originally filed her lawsuit in December 2014, but the case was put on hold while various criminal investigations played out.

The civil trial was shown a videotaped deposition of Cosby taken in 2015 in which he denied the assault, and insisted that he would never engage in sexual activity with an underage girl.  

His lawyers made much of apparent discrepancies in Huth's story, including that both teens spent up to 12 hours at the mansion after the alleged assault.

They also argued that Huth originally claimed the attack happened in 1974 when she was 15, but later said it had happened the following year.

The case was never prosecuted criminally as the statute of limitations had passed by the time Huth spoke to police.

California law allows adults who say they were sexually abused as minors, but have only recently become aware of the damage, to bring civil cases years after the statute of limitations would normally have expired.

Cosby was a towering figure in late-20th century American popular culture, and hit the big time as affable obstetrician and father Cliff Huxtable on "The Cosby Show," which ran from 1984-92.

But around 60 women, many of them onetime aspiring actresses and models, have publicly branded Cosby a calculating, serial predator who plied victims with sedatives and alcohol to bed them over four decades.