Bill Cosby's chief accuser has begun testifying at his sexual assault trial, telling jurors that the entertainer drugged and violated her at his suburban Philadelphia home in 2004 after earning her trust as a mentor.

Andrea Constand said Tuesday that she felt paralyzed and helpless as Cosby groped her breasts, penetrated her with his hand and placed her hand on his penis.

The 79-year-old comedian stared down at the defense table, resting a hand across his forehead, as Constand described the encounter. The TV star once dubbed America's Dad could get 10 years in prison if convicted.

She says Cosby assaulted her after giving her three blue pills he claimed were a natural remedy to ease her stress about a looming career change.