A Massachusetts man already accused in Maine state court of raping an intellectually disabled woman at his family camp in Sebago pleaded guilty Tuesday to a new federal charge of possession of child pornography.

William Duffy, 58, of Attleboro, appeared in U.S. District Court in Portland and waived his right to have the federal case against him presented to a grand jury.

As the Cumberland County Sheriff’s Office investigated the allegations that Duffy had raped the disabled woman at his parents’ camp last May, they seized his laptop computer and discovered it contained many child pornography images and videos, according to a prosecution document filed in federal court.

His sentencing date was not immediately available. He faces up to 20 years in federal prison on the child pornography charge.

Although Duffy has pleaded guilty in the federal case, he still faces a 54-count indictment on state felony charges. He is next scheduled to appear in court on the state charges, which range from gross sexual assault to possession of sexually explicit material, on June 14.

In the state case, Duffy is accused of having an online chat with the 31-year-old woman over three weeks last year on a website for abused women. The woman complained of being abused and denied medication at her group home in Carver, Massachusetts.

Duffy offered to help her escape, the sheriff’s office said. She sneaked out and the pair drove to a camp in Sebago.

Police said Duffy then had sex with the woman, who told an investigator she did not feel she could say no.

Police said the alleged victim appeared to have the intellectual capacity of a 9-year-old. Still, she was able to surreptitiously call police on a cellphone last May 2 and hide the phone under her pillow as she and Duffy were having sex.

Cumberland County sheriff’s deputies working with the Regional Communications Center in Gray traced the call to Northwest River Road in Sebago where they found Duffy and the woman.

Deputies executing a search warrant discovered a backpack containing sexual devices and other items, including heavy-duty plastic zip ties, a “pet safe” shock collar, two rolls of duct tape and two 100-foot lengths of rope.

During the encounter, Duffy threatened the woman and said if she did not have sex with him he would tie her up and have sex with her anyway, the sheriff’s office said. Duffy also told her he was taking her to Rhode Island, which is where she thought she was, the sheriff’s office said.

Police say other items they found have led them to investigate whether Duffy molested any other victims.

Police found a plastic bag from the store Amazing Intimacies that contained, among other things, a “Hello Kitty” child’s nightgown and a pair of panties that had been worn.

Each of the gross sexual assault charges and the unlawful sexual contact charges is punishable by up to 10 years in prison. Each of the charges of possession of sexually explicit materials is punishable by up to five years in prison.

Scott Dolan can be contacted at 791-6304 or at:

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Twitter: @scottddolan