KENDALL - A Whatcom County man has pleaded guilty to assault with a sexual motivation, a misdemeanor, in the rape of a mentally disabled young woman he was supposed to be babysitting.

David Wayne "Bear" Pen, 54, had been in jail awaiting trial since his arrest. He has already served a 10-month sentence handed down last week by Judge Steven J. Mura, and is no longer in custody.

On the morning of Dec. 27, 2011, the victim's mother was out of town for the day, so Pen was alone with the woman in a trailer in the Paradise area. Pen started touching the 18-year-old woman's breasts and buttocks, then asked her to go to bed with him, according to charging documents.

The woman hesitated but agreed because she was afraid "something bad would happen if she didn't go to bed," wrote Deputy Prosecuting Attorney Eric J. Richey. Pen undressed her and told her not to tell her mother.

Then he offered the woman an animal in exchange for sex, Richey wrote. When she declined, Pen sexually assaulted her.

Family members later told deputies the woman is "mentally retarded and autistic to a high end." Pen was arrested two days after the assault. At the time he denied having sexual contact with the woman.

In a plea deal, charges of rape in the second degree were dropped to fourth-degree assault with a sexual motivation, a gross misdemeanor.

Pen, who also uses the alias David S. Benson, had felonies on his record for violating protection orders and for hit and run. He's not allowed to be within 500 feet of the sexual assault victim until July 2015.

Reach CALEB HUTTON at caleb.hutton@bellinghamherald.com or call 715-2276.