A former Iowa state lawmaker is set to appear in court Wednesday to face charges for allegedly sexually assaulting his 78-year-old wife while she was in a nursing home.

According to prosecutors, Donna Lou Rayhons was incapable of consenting to have sex with her husband, Henry, due to Alzheimer's and Dementia.

After previously being widowed, Henry and Donna met in church and got married seven years ago when they were both in their 70s. During their time together, Donna was diagnosed with Alzheimer's and was put in a nursing home by her family members. Eventually, Henry was told by staff that his wife was no longer mentally capable of legally consenting to have sex. However, state prosecutors say the former Iowa House of Representatives ignored that message.

According to a state affidavit, Henry confessed to having "sexual contact" with his wife on May 23. A state crime lab also found semen stains on Donna's quilt and a sheet that matched Henry's genetic profile, Bloomberg News reported.

Two months later, Donna lost her four-year battle with Alzheimer's and died at the facility last August, just days before her 79th birthday. A week later, Henry was arrested on charges of sexual abuse, reports The Washington Post.

Experts say that Henry's trial is a rare and possibly unprecedented case that will explore the question of when a previously consenting spouse suffering from dementia is no longer able to say yes to sex.

Mark Kosieradzki, a Minneapolis-based attorney who has tried numerous cases of sexual abuse in nursing homes, said he has never seen a rape case in which a previously consenting spouse could no longer legally acquiesce.

"This is the first one I've seen," he said, according to The Associated Press. "It's a case that's going to be focusing on the rights of the vulnerable. Just because you're married, it doesn't mean you need to check your consent rights at the door."

Likewise, Katherine C. Pearson, a professor of elder law at Penn State University, told Bloomberg News that this is the first case of its kind she's seen in more than 20 years of working in the field.

"This is maybe the last great frontier of questions about capacity and dementia," she said. "... Any partner in a marriage has the right to say no. What we haven't completely understood is, as in this case, at what point in dementia do you lose the right to say yes?"

Iowa law defines an act as sexual abuse in the third degree if the two parties are not living together as husband and wife and if one person "is suffering from a mental defect or incapacity which precludes giving consent."

However, Elizabeth Edgerly, a clinical psychologist who serves as chief program officer for the Alzheimer's Association, said determining capacity is challenging.

"Is the person capable of saying 'no' if they don't want to do something? That's one of the biggest pieces," said Edgerly. She added that "For most people with dementia, even long into the disease, they take comfort in being with people who love them."

In a statement, Henry's relatives dismissed the notion that any contact between him and his wife could be considered rape.

"Donna's location did not change Dad's love for Donna nor her love for him. It did not change their marriage relationship. And so he continued to have contact with his spouse in the nursing home; who among us would not?" it read. "... Accusing a spouse of a crime for continuing a relationship with his spouse in a nursing home seems to us to be incredibly illogical and unnatural, as well as incredibly hurtful."