Comedian Bill Cosby goes on trial for sexual assault on Monday in Pennsylvania, the culmination of years of allegations that have torpedoed his show business career.

Cosby, 79, once a beloved entertainer known for his family-friendly brand of comedy, is accused of drugging and sexually assaulting Andrea Constand at his home in 2004.

Constand, a former basketball player at Cosby's alma mater Temple University and more than three decades his junior, will appear as the prosecution's key witness during the trial, which is expected to last two weeks.