PORTLAND — Steven Ricci, a Portland man whose violent sexual desires have alarmed authorities, was convicted today on the misdemeanor charge of indecent conduct.

Ricci, 47, was arrested in August after a woman reported that a man was masturbating on a trail in the Fore River Sanctuary.

Because Ricci has had two prior convictions for indecent conduct in the past 10 years, he faces a penalty of a year in prison rather than six months in the current case.

Ricci has previously described to authorities his plans to commit sexual assault. In 2006, he was charged with attempted sexual abuse of a minor but eventually pleaded guilty to the lesser charge of indecent conduct.

Ricci’s family says he was born with cerebral palsy and has other mental disabilities. Ricci has expressed a desire to receive treatment to deal with his impulses.