A former employee at a state-run institution in Boulder that caters to the developmentally disabled has pleaded guilty to sexually assaulting a female client.

Allen Whetstone, who worked at the Montana Developmental Center, was arrested after a patient said he lured her into a room and sexually assaulted her in May 2010. As part of a plea deal, the 49-year-old Whetstone acknowledged exposing himself and rubbing his genitals against the victim.

Jefferson County Attorney Matt Johnson says he believed he had enough evidence to charge Whetstone with raping two other clients, but their guardians said it would be too traumatic for the alleged victims to testify.

Whetstone, who is to be sentenced Aug. 10, faces up to 10 years in prison and a $10,000 fine for the felony charge. He also must register as a sex offender.