Fifty-three police officers have been disciplined after failings surrounding missing person investigations in Northern Ireland, the Ombudsman said.
Some PSNI members did not properly assess reports and there were further problems with supervision and searches plus missed opportunities to gather evidence, the watchdog said.
Police Ombudsman Dr Michael Maguire said the force needed to rethink how it handled such investigations, but acknowledged very few of the 13,000 reports it deals with a year reached his office.
He said: "Yet some of the failings we identified in 2010 were still happening in 2015, which represents a real risk to public confidence in the way police deal with missing persons investigations."
Between 2010 and 2016, the ombudsman's office investigated police handling of six separate missing person reports and recommended 55 officers be disciplined.
Fifty-four were disciplined, one overturned it on appeal. Another officer retired before the sanction could be administered.
Dr Maguire said the PSNI should establish a central unit offering specialist help.
He also urged the force to consider reminding officers of guidance that anyone whose whereabouts are unknown must be recorded as a missing person and not as a concern for safety or suspicious issue.
The watchdog established a string of lapses in how police responded to reports that Geng Feng Shi, a 23-year-old Chinese man, was missing.
His body was found in the River Lagan at Belfast Harbour in March 2015.
Ombudsman investigators found that although it was likely that Geng Feng was no longer alive by the time he had been reported missing, the way in which police responded to concerns about him included some common failures.
Geng Feng had been assessed by a psychiatric doctor in hospital.
Police had seen him twice behaving abnormally, once lying in the street singing and once at a cemetery refusing to communicate.
Despite this, when his family rang them to say they could not contact him he was not logged as a missing person.
The Ombudsman said: "This decision was a fundamental failure, given PSNI guidance. It resulted in an unacceptable delay in police undertaking proactive and robust enquiries."
The investigation recommended 14 officers be disciplined.
A senior officer said new guidelines to police officers and staff were issued after this case.
Assistant chief constable Alan Todd said: "This is not just a challenge for the police service but also other statutory agencies, who, like the PSNI are faced with an increasing number of people suffering from mental health issues and decreasing resources and facilities to deploy in relation to them, and indeed the very many other demands on daily service provision."
Work with other agencies will focus on prevention, early intervention and risk management and in improving safeguarding in such cases.
In the financial year 2016-17, PSNI investigated 12,821 reports of missing persons - an increase of 5.2% from the previous year and a figure which is increasing year on year.
On average there are approximately 35 missing person reports made daily to police.
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