A 25-year-old man who was an aide at a mental health center has been arrested on charges he had a sexual relationship with a 13-year-old patient.

Elzie Karlo Harty, 25, was arrested Tuesday on a felony charge of child molesting. Authorities say he met the girl in March 2005 when she began seeking treatment at the Anderson Center and that the two were having sex within a month.

"He used his position to take advantage," Madison County Prosecutor Rodney Cummings said. "It's really, really disappointing and a pretty serious betrayal of trust."

Harty was being held in the Madison County Jail under $35,000 bond. He shook his head "no" while the charges against him were being read during an initial court appearance.

Harty worked until May 3 as a therapist assistant at the mental health center, which provides adolescent residential treatment for those ages 11 through 18 with emotional and behavioral difficulties.

The center's staff notified investigators of the case and has been cooperating with the police, said Jennifer Atkinson, a spokeswoman for the center's parent company, St. John's Health Services.

Anderson police Detective Joel Sandefur said the teen's counselor turned over handwritten notes between her and Harty to Madison County Child Protective Services, which then contacted the police. The teen told investigators that she and Harty had sex in her room at the center about 10 times while he was conducting room checks.

"When the victim received a weekend pass, Harty would call the victim, make arrangements to pick her up in his vehicle, and then take her to his residence in Muncie where the two would have sex," Sandefur said.