Editor's note: This report includes graphic and disturbing descriptions of sexual assault.

The victim couldn't tell anyone what happened that night. She was a woman with an intellectual disability who doesn't speak words. So the alleged rape was discovered, according to the police report, only by accident — when a staff worker said she walked into the woman's room and saw her boss with his pants down.

Early in the morning on Nov. 13, 2016, police were called to the cottage at the Rainier School, a state institution in rural Washington, for adults with intellectual disabilities. They arrested Terry Wayne Shepard and took him to the police station. Shepard, the longtime supervisor in the building, denied that he'd had sex with the disabled woman. Police wanted a DNA sample for testing; Shepard said, according to the documents that charged him in court, that he had already given his DNA sample "in regard to a previous sexual assault allegation 2 to 3 years ago."

NPR investigated sexual assaults against people with intellectual disabilities. We found that they are some of the easiest and most frequent victims of sexual assault. Their risk is at least seven times the rate for people without disabilities. That comes from unpublished U.S. Department of Justice data obtained by NPR. And that estimate is almost certainly an undercount. For one thing, many victims — such as the woman at the Rainier School — can't talk or have difficulty speaking. So they can't report a crime.

Another reason the real number is likely higher: The federal data do not include the 373,000 people who live in group homes. Nor do the data count people who live in state institutions — where other research shows the risk is higher. So the woman at the Rainier School would not have been counted.

"It's a crime scene"

It's a long trip for Cathy McIvor, from her home in Arizona to the state institution in rural Washington where her sister, Maryann, lives. It's a sunny morning, and Mount Rainier looms, large and luminous, as McIvor drives down the long road to the Rainier School in Buckley, Wash. And when she gets there, the staff has Maryann dressed and ready — and waiting by herself outside the one-story cottage where she lives.

Maryann doesn't communicate with words. But when she spots her sister driving down the road her face lights up and her whole body moves with excitement, and she makes sounds of joy.

But McIvor refuses to go inside this cottage where her sister lives. She doesn't want to see her sister's room — because of what happened there months before. "It's a crime scene. Let's get real here. It's a crime scene. For how many years? Who knows? Who will ever know?"

Maryann is the woman who was the victim of the alleged rape on that November morning. NPR does not use the last names of survivors of sexual assault, unless they prefer their full name be used.

McIvor stays outside. But Maryann wants to show her room. She is thin, almost fragile. Her hair is short, her shoulders hunched forward. She keeps her elbows bent and her hands close to her chest or face. She takes radio producer Anna Boiko-Weyrauch by the hand and leads her down the hall to a small room with a sign on the door that says "Maryann." It's the room she shares with another woman. Maryann is 58. She has lived at the Rainier School since she was a teen.

Maryann wants to show the journalist her pink bedspread. It's new since what happened here in November. And the framed pictures of magnolias on the wall. They're new, too. A staff person, who has cared for Maryann for decades, took her to the store to buy them.

A speech pathologist here taught Maryann a few dozen signs. Hungry. Thirsty. Hamburger. Maryann puts her hands just under her eyes and flips them. It's her sign for "happy." And she lets out a loud, hearty laugh.

"What did I do?"

It was just Hunter Shear's second week on the job, covering the night shift at the small building that was home to a few dozen adults with intellectual disabilities. She was just 20 years old, and after a couple weeks of training she had been assigned to the overnight shift of the cottage called 2005 House. These details come from the police report. At around 1 a.m., Shear went looking for her supervisor to get permission to take a break.

Terry Wayne Shepard, the night supervisor, had worked at the Rainier School for 34 years, 20 of them in this small cottage. He had assigned Shear to the men's wing. He took the women's wing.

Shear told police she walked down the hall and found Shepard — in Maryann's room. She said her shoe squeaked on the floor. She said her supervisor — startled — turned around. According to the prosecution's document that charged him, he saw her, and said: "Oh, s***."

When officers from the Buckley Police Department arrived, Shear's eyes were red and watery, and she was taking short, shallow breaths. Shepard was sitting calmly on a couch. "What did I do?" he asked the officer.

The police report details what Shear says she saw. An officer wrote: "Shear advised me that Shepard had his pants and underwear down around his knees. Shear advised me that Shepard had the client's legs pinned up to her chest and that he was making back and forth movements like he was having sex. ... Shear told me that she saw Shepard's erect penis come out from between the client's legs when he turned around ..."

Police arrested Shepard for suspected rape and took him to the station. There, he denied what Shear said she had seen. He "denied all allegations of sexual contact" with the disabled woman.

Other allegations

Maryann's sister, Cathy McIvor, got a phone call at her home in Arizona, telling her it was feared her sister had been assaulted.

She then tracked down Maryann at the hospital, where she had been taken to be examined for rape. McIvor called the aide who was with Maryann. And the very first thing the aide did was to express her suspicion about Shepard. McIvor remembers the woman telling her, "I don't know why they've left him on the hall; he's had a prior sexual allegation."

That angers McIvor. "So why would they leave this man on a hall, with developmentally [disabled] female residents, at night? On the graveyard shift?"

Indeed, there had been suspicions about Shepard, but until that night, never a formal charge against him.

Prosecution documents show that at the police station early that morning, officers wanted a DNA sample from Shepard.

Shepard said: You've already got my DNA. From another sexual assault allegation two or three years ago. That's according to prosecution documents.

Washington state officials, with the Department of Social and Health Services, said they can't talk about the alleged rape of McIvor's sister because it's a pending legal matter.

But Lisa Copeland, a spokeswoman for the department, said that in the earlier rape allegation, several male staffers — including Shepard — were asked to submit DNA samples. No match was found, for Shepard or any other staffer. Shepard and the others were cleared.

Copeland says that happened not a few years ago as police say Shepard said, but in 2006.

The state agency took all allegations seriously, Copeland says. And she told NPR about a previously undisclosed allegation against Shepard: The state got an anonymous tip that Shepard "had an affair" with a resident at a private nursing home, where he also worked as a bus driver. The spokeswoman says: "The allegation was investigated and found to be untrue." That one, too, was about a decade old, from 2007.

The day after Shepard was charged with the rape of Maryann, the Washington state agency in charge of regulating state institutions — the Division of Residential Care Services — sent a team of investigators to the Rainier School.

And right away, they found more allegations against Shepard. The report from RCS was first uncovered by Disability Rights Washington, part of a national and congressionally funded network of lawyers who represent people with disabilities. The report describes the alleged rape that night of Maryann and how she was taken to the hospital for a rape exam, although it doesn't use her name.

NPR showed the state agency's report to McIvor, the first time, she said, she had learned of it.

According to the report, state investigators showed up at the Rainier School and, right away, another woman with an intellectual disability who lives there came forward and said the same man assaulted her. Prosecutors say this woman — 66 years old — said Shepard hit her in the head, that he had touched her breasts and what she called her "private spot." Still, the woman was nervous and "very worried" that she would get in trouble for telling on Shepard.

And that wasn't all. The report says staff at the institution told the investigators that they suspected there were other potential victims. They said, according to the report, that Shepard cared for a couple of women who had been acting out lately, and that one of the women was getting extra attention from Shepard. According to the report: "One potential victim received 'treats' and 'extra showers' from the staff member."

Copeland, the Social and Health Services Department spokeswoman, says those suspicions were then investigated, but no proof was found.

Shepard was charged with rape of Maryann and for taking "indecent liberties" with the second woman who came forward.

Shepard's trial is scheduled to begin on Jan. 25. McIvor brought a separate lawsuit — a civil suit for damages — against the state, and that goes to trial next year. State officials say they can't comment on the civil lawsuit.

Shepard, who is sitting in jail awaiting trial, did not respond to a letter from NPR. His attorney says the allegations will be "fully contested" in court.

The state oversight agency's investigation faulted the Rainier School for failing to protect residents. In a report, it said administrators knew there was a problem but didn't take basic steps to prevent more abuse. Staff wasn't trained to spot abuse. And when assaults were discovered or suspected, the victims got no therapy or support.

The institution was forced to make changes. Its "correction plan" included better training of staff and more monitoring of the night shift, including unannounced visits.

And federal auditors, separately, have found other widespread problems at the Rainier School — including poor medical care that led to illness and possibly deaths. In December 2016, federal Medicaid stopped reimbursing the institution for any new resident it admitted.

NPR collected data from state agencies that are tasked with providing services and protecting people with intellectual disabilities. We asked how often these state agencies got reports of suspected sexual abuse of someone with an intellectual disability. States have an obligation to then try to determine whether those allegations can be substantiated.

In Texas, fewer than 1 percent of allegations were confirmed. In Florida, about 5 percent were verified. In Ohio, 23 percent were substantiated between 2012 and 2015. In Pennsylvania, 34 percent of allegations were confirmed.

Across the country, we found multiple cases of victims who couldn't speak or say what happened. Cases where a suspected rape was uncovered only because of some unexpected proof.

In Charlotte, N.C., a mother gave her daughter a bath and found bruising.

In Missouri, an intellectually disabled woman went to the doctor, who discovered she was pregnant.

And in Boynton Beach, Fla., detectives reopened the cold case of a woman who got pregnant 13 years ago. Last June, detectives ran a DNA test, got a match and arrested a man. But in November, a judge threw out the case because the statute of limitations had expired.

"She can't tell us what's wrong"

Natalie's family was worried and puzzled when Natalie stopped sleeping through the night. It was 2011, and Natalie's mother and sisters could tell something wasn't right. In her room, filled with over 100 dolls and stuffed animals lining the bookshelves, bureau tops and corners, Natalie moaned through the night. She has a significant intellectual disability and is unable to use words.

She couldn't sleep. She'd sit up on her knees in bed. She couldn't lie down.

Natalie, who is 35, spends her days at the family's house in Northern California. Her mother and her sisters do pretty much everything for her — feed her, dress her, put her on the toilet, give her medication — all day and night.

"There was something she couldn't tell us," says her mother, Rosemary. "But we had her multiple times at the doctor's. Almost every month there was something going on with her. And she can't tell us what's wrong."

Doctors treated Natalie for sinus infections, for yeast infections — for more than a year. But the pain kept coming back.

Until one day, a new doctor at an urgent care center — a woman — tried a test no one had thought of before.

The doctor's office called Natalie's sister Julie Neward. "I'll never forget when I got the news," she says. "It was right after I got off of work. Probably left early that day due to traffic. Maybe around 4 o'clock and I was on ... Mission Boulevard."

The news shocked her. "And they said, 'Julie, you need to bring your sister Natalie in.' And I said, 'OK, why?' 'She's been diagnosed with gonorrhea.' And I'm like: 'What? No, that's not possible.' She's like a baby. She doesn't even kiss people. I cried the entire way home."

Police did investigate. They interviewed men at an outside care facility. There were no men at the house where Natalie lived. Natalie couldn't tell detectives what happened. The investigation went nowhere. No one was ever punished. No one was ever stopped.

The assault continues to haunt Natalie and her family. Natalie continued to have nightmares. Rosemary took on the full-time care of her daughter. And another daughter, Patricia, put her own career on hold, to help out with the round-the-clock care. Julie co-founded the California chapter of the Sibling Leadership Network, an advocacy and support group of people who have a family member with a disability.

"But she has feelings"

Cathy McIvor struggles, too, with what's best now for her disabled sister. She thinks about moving Maryann away from the Rainier School, away from the cottage where she was allegedly raped.

The reason McIvor has driven to the Rainier School on this day is to talk to the staff psychologist. She wants to know how he thinks Maryann would react to a move. But while she's in the car, the psychologist calls. He says he can't meet with her.

McIvor thinks of moving her sister out of Washington state and to Arizona where McIvor lives with her husband. But it's not easy. Maryann gets Medicaid services in Washington state. She would have to establish residency in Arizona to become eligible for similar services there.

And the Rainier School is Maryann's home, the place she has lived for around 40 years. She has had the same roommate for 20 years. It angers McIvor that a staff person is charged with raping her sister. But McIvor knows there are also many staff people here, too, who care about her sister and whom her sister relies upon. One aide has worked with Maryann for 25 years and is the person who knows her best. She was the one who took Maryann shopping for the new bedspread and pictures to put on her wall.

And it was that aide who took Maryann to see her mother as she was dying.

Three weeks after the alleged assault, Maryann's mother died. Cathy McIvor never told the dying woman about what happened at the Rainier School that night.

But the mother's death was another trauma, right away, for Maryann. Before her mother died, Maryann went home every month for a few days to stay with her. But when her mother died, the house was sold. McIvor says Maryann can't understand why she doesn't see her mother anymore. Even though she went to the funeral. Even though McIvor takes her to the cemetery. And Maryann can't understand that her home is gone.

"Home." It's one of the few words Maryann can sign. And on this day, Maryann signs it over and over. Her fingers and thumb together, moving from cheek to ear.

And then she signs another word she knows: "Mom."

"No Mom," McIvor says, looking into her sister's eyes.

"She's still doing that," McIvor says, and sighs. "I'd hoped that ... going to the cemetery to see the cemetery plot would have helped."

Maryann spreads her hand, with her thumb to her chin.

"That's the sign for Mom," McIvor says. And then to her sister: "And where is Mom? You know. We won't see Mom ever again. You know that."

McIvor explains: "But she has feelings.

"Don't you, honey?

"Like everybody else. Don't you? Sad and mad and angry. I know you do.

"She does."

Then McIvor drives with her sister to Maryann's favorite restaurant, for a hamburger, her favorite lunch.

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