A pretty nightie, a new lipstick, a fresh toothbrush: Doris Racher noticed that small things she had bought for her 96-year-old mother, Eryetha Mayberry, a dementia patient at a nursing home in Oklahoma City, had been disappearing. Racher assumed the culprit was another resident who sometimes wandered into her mother’s room and fell asleep in her bed.

So in 2012, Racher placed a motion-activated camera in her mother’s room. It looked like an alarm clock, and Racher nearly forgot about it.

About two months later, the family decided to pore through the recordings.

The camera had not caught the petty thief. But it captured something else:

An aide stuffed latex gloves into Mayberry’s mouth, while another taunted her, tapping her on the head, laughing. Hoisting her from her wheelchair, they flung her on a bed. One performed a few heavy-handed chest compressions.

“My niece started bawling and couldn’t watch anymore,” said Racher, 78.

“I was furious.” Mayberry died soon after.

On November. 1, propelled by the outcry over the Mayberry case, Oklahoma became the third state — along with New Mexico and Texas — to explicitly permit residents in long-term care facilities to maintain surveillance cameras in their rooms. In the last two years, at least five states have considered similar legislation.

Although some states have administrative guidelines for electronic monitoring, most legislative efforts have stalled because of questions about liability and, in particular, privacy rights, raised by facility owners, unions, elder care lawyers and families.

Despite such concerns, not only have family members turned to these “granny cams” — a popular nickname that some consider patronising — but even the government has used them.

A year ago, the New York state attorney general’s office, which has relied on hidden cameras in patient abuse and neglect cases for years, demonstrated its methods at a national training program for state investigators.

In June, Mike DeWine, the Ohio state attorney general, announced that his office, with permission from families, had placed cameras in residents’ rooms in an unspecified number of state facilities. DeWine has moved to shut down at least one facility, in Zanesville, where, he said, cameras caught actions like an aide’s repeatedly leaving a stroke patient’s food by his incapacitated side.

The recordings can have an impact. Based on Racher’s videos, one aide pleaded guilty to abuse and neglect. The other appears to have fled the country. Similar scenes of abuse have been captured in New Jersey, New York, Pennsylvania, Texas and other states by relatives who placed cameras in potted plants and radios, webcams and iPhones.

The monitoring is often a last-ditch step by relatives who suspect abuse but feel that the authorities dismiss their complaints.

“Families are witnessing injuries and neglect of loved ones, and the only way to detect what’s happening is to use hidden cameras,” said Wes Bledsoe, the founder of A Perfect Cause, a group based in Oklahoma that tracks such cases around the country.

Although no one tracks its use, the technology is accessible, affordable and widely accepted, said Dan Frith, a lawyer in Roanoke, Va., who represents plaintiffs in neglect and abuse cases against long-term care facilities.

“I’m confident there are numerous granny cams in nursing homes in Virginia that people never discuss with the staff,” he said.

“It’s a cheap, quick way to verify.”

But the secret monitoring of a resident raises ethical and legal questions. Families must balance fears for their relative’s safety against an undignified invasion of their privacy. They must also consider the privacy rights of others who pass through the room, including roommates and visitors.

Proponents of hidden cameras argue that expectations of privacy have fallen throughout society: nanny cams, webcams and security cameras are ubiquitous.

But others say that it is one thing to videotape a nanny in one’s home who is putting a diaper on a nine-month-old, and quite another to record an aide doing so for a 90-year-old.

“This is infringing on someone’s privacy arguably for their own benefit,” said Nina A. Kohn, a law professor at Syracuse University.

“We have to be especially careful that it’s justified.”

A long-term care resident often lacks the capacity to consent to being recorded, so the decision is usually made by a representative, who may not be a relative. That decision maker has to stand in the resident’s shoes, Kohn said: If the resident were mentally capable, would he or she agree to round-the-clock monitoring of many intimate moments — being bathed, put on the toilet, even having sexual relations with another resident?“Racher said she never worried about violating her mother’s privacy.