A former psychiatric nurse-counselor at Taylor Manor Hospital in Ellicott City was sentenced yesterday to two years in prison for sexually assaulting a teen-age girl who had been admitted there for treatment for post-traumatic stress.

Alvin Tyrone Williams, 41, abused a young woman who was vulnerable and could not fend for herself, Howard Circuit Judge Lenore R. Gelfman said before imposing a five-year term, suspending all but two years. Gelfman also placed Williams, who pleaded guilty to attempted third-degree sexual offense in June, on five years' probation.

"The people there are put there because they are vulnerable. They are ill. He's the adult," Gelfman said. "This is a big deal."

Williams, of Gwynn Oak in Baltimore County, had been working at the psychiatric hospital for two years at the time of the incident July 8 last year. The girl, then 15, had been admitted the day before.

Prosecutors said Williams asked the girl inappropriate questions about sex. While the girl's roommate was away from their room, prosecutors said, he entered the room and sexually assaulted her.

Williams later told police that he had a sexual encounter with the girl, and his DNA was found in a sample taken from a hospital gown the girl used, prosecutors said.

Williams was in a "position of trust," said Assistant State's Attorney Amy Hott Somerville, who argued for a full five-year term.

"The defendant took advantage of a troubled child, a child who was at Taylor Manor for treatment, not to be sexually molested," Somerville said. "Her mother put her there for help."

Yesterday, Williams' lawyer, Roland Walker, told Gelfman that his client maintains that the girl instigated the sexual encounter -- a version of the story prosecutors say the girl denies -- and that Williams was never trained to handle such situations.

"He did not have the fortitude to back off and handle it in a more professional way," said Walker, who asked Gelfman to place his client on home detention. "He should have known better. He should've backed off."

Williams, a married father of three, apologized, and said that he was "at a bad place at the wrong time" and made a "terrible decision."

After the hearing, the girl's mother said the whole incident has been "hell." The Sun is not naming the mother to protect the girl's identity. The girl, who is now 17, is adopted and was being treated to help her deal with issues from her early childhood, the mother said.