TORONTO -- Mary McAlpine was fiercely independent her entire life. But by the time she was in her 80s, she was getting frail.

"Well, she just got so it was very difficult for her to take care of herself that was the bottom line," said her daughter, Pat Poirier.

So, like many elderly Canadians, Mary came to live at Hillsdale Estates, a long-term care home in her hometown of Oshawa, Ont., a place where she was happy and safe, or so her family thought until a phone call in June of 2008.

Her son, Gaylord McAlpine, remembers the shock. "'We had an incident with your mom. Another patient had assaulted her.' And I thought, you know, he poked her hair or bumped her or something… and then they explained it was sexual assault and I just went, 'Whoa.'"

Mary McAlpine had been sexually assaulted by another resident, a man named Geert Flonk. And she wasn't alone; three other women had been sexually assaulted.

But it was worse. It turned out that Flonk was a sex offender. He had been convicted back in 2003 of sexually assaulting a young woman with a mental health condition in Bowmanville, Ont. He was eventually sentenced to a year in jail and three years probation. In fact, he was still on probation when he ended up at Hillsdale in Oshawa. But no one at the home knew that.

Retired Durham Regional Police officer John Keating investigated those assaults as a member of Durham's elder abuse team.

"When I learned that he had already been convicted of a similar assault, it bothered me immensely," he said. "I kept thinking: if I had a grandmother and that happened, how would I feel about it? I would be infuriated. Especially knowing there is a history."

The Long-Term Care Homes Act in Ontario requires homes to report any violent incidents to the province and call police to investigate. Keating says people have no idea who is living down the hall from their loved ones. And there are a lot more people with criminal records than the public is aware of.

Every staff member working with vulnerable people in long-term care has to agree to a criminal background check. And Keating says the same should apply to residents.

The associate minister responsible for Long Term Care in Ontario, Dikpika Demerl, told W5 that the province has zero tolerance for violence and that they do a careful behavioural and needs assessment of every resident at placement.

But when it comes to background checks, "I really need to be clear that in Ontario to access health care, we don't say you need to provide a police record," said Demerl.

Mary McAlpine's children disagree. They went to court with W5 to get a publication ban lifted which protected the identity of Flonk's sexual assault victims, because they wanted to tell Canadians about what happened to their mother.

Pat Poirier says her mom would expect that. "To make sure the vulnerable people in our society are protected…I believe in privacy. But I do not believe in privacy at the expense of vulnerable people."