Elderly men and woman living in Australian nursing homes are being killed or fatally injured by their fellow residents.
A string of 28 deaths has been uncovered by Melbourne researchers. The cases are not considered murders, but mostly tragedies where people with dementia have become confused and argued with each other, with fatal consequences.
"Some people were classifying these as homicides but we don't believe there is intent behind this," said Professor Joseph Ibrahim from the Victorian Institute of Forensic Medicine and Monash University.
"It's typically two people with dementia getting involved in an argument or concerned about one invading another person's space.
"You have one person that pushes the other. The other person falls, breaks their hip or hits their head, and because they are in their eighties and frail, they don't bounce back.
"They end up dying."
In the largest international study of its type examining coroners' files, at least 15 elderly women and 13 elderly men were found to have died following incidents of "resident aggression" in Australian nursing homes between 2000 and 2013.
With the instigators of the aggression mostly suffering from a mental disorder, the issue has proven to be a fraught one for police and the legal sector.
Only two of the 28 deaths resulted in criminal charges and in both incidents the accused died before the case got to court. In other cases, police found the person not fit to be interviewed, or that pursuing a prosecution was not in the public interest.
Almost 90 per cent of the residents who died, or were the instigators of the assault, had dementia. And about a quarter had schizophrenia - a finding that the Melbourne researchers said was troubling given the rising prevalence of mental health problems in the nursing home population.
Close to 90 per cent of victims were aged 75 or older and most of the deaths happened after a resident fell as result of being pushed or punched.
Researchers warned there are likely to be many serious but non-fatal assaults between residents of nursing homes that go unreported, with other research suggesting that at least 20 per cent of residents exhibit aggressive behaviour.
"[While] 28 deaths nationally over a 14-year period sounds quite small ??? it is just really the tip of the iceberg of other incidents that occur on a daily basis and either don't get reported or don't result in a death," said Monash University researcher, Briony Murphy, who led the study.
Exactly how common these incidents are is unknown, said Professor Ibrahim, who is calling on the federal government to adopt the recent recommendation of the Australian Law Reform Commission to require aged care providers to report any allegation of a serious incident to an independent body.
He said the deaths following disagreements between dementia patients (often sparked by minor encounters such as a person wandering into the wrong bedroom) were all "horrible or sad".
"We have them in residential care where we should be looking after them and we have this awful situation occur.
"It's just tragic.
"What are we doing about this? The frustrating is we don't seem to be doing very much."
However, Pat Sparrow, chief executive of Aged and Community Services Australia said there were protocols in place.
Ms Sparrow said facilities had to report any physical or sexual assault involving aged care residents to the health department and the police within 24 hours.
When a resident has an assessed cognitive impairment such as dementia "the provider doesn't have to report it, but they have to put in care arrangements and that has to be done to manage the behaviour within 24 hours", she said.
"Then the provider keeps a record or log of what the incident is and what they have done to manage the process," Ms Sparrow said.
Aged Care Minister Ken Wyatt said the Turnbull government was considering a recommendation to enact a serious incident response scheme for aged care.
"This recommendation builds on the existing reporting of allegations of abuse in the Aged Care Act to include residents with pre-diagnosed cognitive impairment," he said.