A profoundly disabled man who died at a nursing home in Northern Ireland may have been strangled, a pathologist has said.
Wheelchair-user Seamus McCollum, 56, had cerebral palsy and was fed through a tube.
He died at the Maine Nursing Home in Co Antrim in September 2011 and marks were found on his face and neck after his death, a doctor told his Belfast inquest.
Northern Ireland's assistant state pathologist Dr Peter Ingram said there were "a considerable number of worrying injuries, principally to the neck or face, for which no satisfactory plausible explanation has been proffered".
He said: "The possibility of strangulation cannot be excluded. The possibility of smothering needs also to be considered."
He said it was highly unlikely some of the injuries were sustained during attempts to resuscitate Mr McCollum.
The keen Manchester United football club supporter spent most of his life in care, from age five.
He had been in the Randalstown home for almost a decade after being moved from Muckamore in Antrim.
He was fed through a peg as he had difficulties swallowing and lifted in and out of bed using a hoist.
Mr McCollum could not control his head and used a board to communicate. Despite his challenges, he was in good form before his death, his sisters said.
Differing accounts have been given of the circumstances of death by care workers at the home.
Ireland's State Pathologist Marie Cassidy was asked to examine post-mortem findings.
She said no satisfactory explanation had been provided for some marks.
There were deep bruises to the neck but no trauma to the skeleton and the cause of death was undetermined.
Professor Cassidy said: "It cannot be excluded that the injuries were caused by a third party."
Staff nurse Mary Harraghy, who carried out CPR, did not notice any marks on him bar a blemish on his collar bone before she handed him over to paramedics.
She believed elastic from the oxygen mask could have caused the damage when he was moved from the bed to the floor by the emergency team.
Another possibility coroner Joe McCrisken is investigating is whether Mr McCollum fell from his bed.
A fit could be another explanation, Mr McCrisken added.
Claire Thompson was one of the last people to see Mr McCollum alive and in a statement she said she noticed yellow marks on his neck after she returned from calling an ambulance because he had became poorly.
She said: "They shocked me and made me feel uneasy."
She was unable to remember many of the details.
Other staff said they had not noticed any bruising on his neck before his death and his sisters Molly Gilbert and Bernadette McFall had no complaints about his care up to that point.
Nurse Valerie McKinney wrote in a risk assessment that "Seamus would be unable to protect himself and others from danger."
She told the Belfast coroners' court: "Seamus would be considered a vulnerable adult."