LOS ANGELES » A man has been charged with raping an 18-year-old mentally disabled woman in the back of a Los Angeles County transit bus last week.

Prosecutors say 20-year-old Kerry Trotter pleaded not guilty Wednesday to one count each of forcible rape and rape of an incompetent person, and two counts of sexual penetration by a foreign object. If convicted, Trotter faces more than 20 years in prison.

Authorities say Trotter and the woman boarded the bus at the same stop last Wednesday and he allegedly raped her in the back of the bus. Trotter was arrested thanks to an anonymous tip by someone who saw an image from a surveillance camera.

He was ordered to remain jailed in lieu of $285,000 bail. It’s not immediately known if Trotter has retained an attorney.