Russell Brand's raunchy British humor and bad-boy image helped launch his career, but now he's facing criminal charges of sexual assault and rape, which he denies. 

The criminal trial of Sean "Diddy" Combs has begun. Prosecutors allege he engaged in a dark underworld of sex trafficking, prostitution and more. The mogul denies all accusations, maintaining his innocence. "IMPACT x Nightline" goes inside the case.