Two Gwent Police officers should have done more to assist a deaf man found dead after they helped him home, a watchdog has ruled.
Anthony Lewis, 52, was helped home after officers found him in the street in Newport.
He had speech difficulties which made it difficult to assess what was wrong, the Independent Police Complaints Committee (IPCC) said.
It ruled the officers should have sought family or medical help for him.
The officers were likely to have been the last people to see Mr Lewis alive, the police watchdog said.
A post mortem examination was unable to establish the cause of his death and an inquest recorded an open verdict.
Mr Lewis was seen by a number of people in Wharf Road, Newport, in the morning of 20 October, 2009 holding onto a lamp post.
Two officers stopped to aid Mr Lewis before escorting him home, said the IPCC.
One of the officers, who took lead responsbility for Mr Lewis' care, has been given a written warning.
Mr Lewis was found dead in his armchair by his mother two weeks later. He was fully clothed and the television was on.
IPCC Commissioner for Wales Tom Davies said the officers had failed in their "duty of care to a vulnerable person".
He said: "This must be a very difficult time for Mr Lewis' family and my condolences go to them. This was a tragic case and Mr Lewis' mother had the additional shock of discovering his body at his home.
"The two police officers who went to Mr Lewis' aid had a duty of care which they did not properly discharge.
"Mr Lewis was described as deaf and also had speech difficulties and therefore relied on lip-reading and sign-language to communicate.
"This made the two officers' task in establishing what was wrong more difficult, but meant they should have done more to ensure Mr Lewis received appropriate care and support.
"Our investigation has found that the two officers were probably the last people to have seen Mr Lewis alive.
"Gwent Police has now issued guidance to all front-line officers in how they should deal with vulnerable people."
One of the officers received a written warning following internal disciplinary proceedings.
A Gwent Police spokesperson said they extended their "deepest sympathy" to Mr Lewis' family.
The spokesperson added: "Gwent Police accepts the IPCC inquiry findings relating to Mr Lewis' care and support."