A Wellington coroner has criticised police and Capital and Coast District Health Board (CCDHB) over the 2007 disappearance and death of a mental health patient.

Andrew Perkins, 43, of Plimmerton in Porirua, suffered from paranoid schizophrenia and was receiving compulsory daily treatment at Porirua's Kenepuru Hospital.

Mr Perkins, who had a history of absconding, fled from hospital staff on the morning of July 11.

In a Coroner's Court report released today, mental health nurse Lynda Simeona said she did not think Mr Perkins was going to kill himself and that he needed to be picked up by police.

Ms Simeona completed the hospital's "awol procedure", notifying police of Mr Perkins' disappearance via fax.

The same procedure was carried out the day before when he disappeared for several hours in the afternoon.

The report said police received the awol notice but it was passed from officer to officer and not actioned for several days.

Due to the delay, the use of police search and rescue dogs was not viable.

Mr Perkins' body was eventually found by members of the public in a creek on hospital grounds - 19 days after he disappeared.

CCDHB psychiatrist Laurence Thomson told the court that Mr Perkins had a 16-year history of mental illness and had been admitted to hospital 21 times.

He suffered multiple delusions, including a belief that he was Jesus Christ and the victim of UFO activity.

Wellington regional coroner Ian Smith ruled Mr Perkins died of accidental hypothermia and made a number of recommendations to both police and the CCDHB.

"It is clear that there were some shortcomings with respect to the expected level of care that Mr Perkins should have received from the Mental Health Agency Services and also with respect with the actions of police," he said.

Mr Smith recommended police and CCDHB work closely to established clear protocols for dealing with missing persons.

He also recommended CCDHB undertake an independent review of its awol procedure, and criticised it for previously abandoning an investigation.

"There appears to be a myriad of specialist mental health subsets that must make coordination very difficult as to who is responsible for what activity. The process might well improve with an independent review."

A fence around the hospital's boundary should also be considered, he said.

Both police and CCDHB identified "areas of concern" and made a number of changes as a result of Mr Perkins' death.

Police made changes to their risk assessment procedures and vowed to work closely with the DHB on its procedures for reporting missing patients.

In a written statement today, CCDHB mental health clinical director Alison Masters said Mr Perkins' death occurred three years ago and a number of changes had been made in that time.

"While the initial review was not completed, our patient safety officer has subsequently carried out another review of the events so we can learn from these and improve the way we deal with such situations in the future," she said.

"We have developed a new missing persons policy, which we are currently consulting on. It includes changes to the way we report missing persons, what our response is, and how we communicate the circumstances relating to individuals so action can be taken."

Dr Masters said CCDHB wanted to draw up a memorandum of understanding with police "to establish a joint way forward".