An Independent Police Conduct Authority investigation has criticised the initial police response to the 2005 death of Dunedin teenager Nicholas Munro, saying the investigation "lacked vigour and direction'' and that police did not give the assault "the attention it deserved''.
The outcome of the Independent Police Conduct Authority (IPCA) investigation - carried out in 2010 - was not previously publicly released.
However, a copy of its findings have been obtained by the Otago Daily Times.
• Man whose punch led to teen's death
The release of the authority's investigation comes as coroner David Crerar's findings into the death of Nicholas Munro, released yesterday, exonerate the decision not to charge the man responsible for his death.
Mr Munro (18) died in Dunedin Hospital on March 11, 2005, five days after he was admitted with head injuries stemming from a fight outside a Frederick St bar.
Mr Munro argued with Samuel Richard Scott over a taxi before the altercation early on March 6, 2005.
Mr Munro was knocked to the ground after he was punched in the head by Mr Scott and fell heavily, hitting his head on the road.
The release of the coroner's findings marked the first time in the almost 11 years since Nicholas' death that Mr Scott's name was released publicly.
He sought an order to prevent publication of his name, but Mr Crerar declined to grant the order.
Mr Crerar said Mr Scott's punch was "out of proportion to the threat posed to him by Nicholas Munro''.
Police investigated the matter twice and did not believe charges were justified.
Mr Crerar supported the police investigation's finding.
The IPCA's investigation cleared the investigating officers of wrongdoing, but said they had fallen short of following best practice.
"The original investigation lacked the perceptive eye of a 'canny' investigator,'' the authority's findings said.
"In the early stages, police failed to give the matter the attention it deserved.
"The initial investigation lacked vigour and direction.''
The authority criticised the initial police response.
The altercation between Mr Munro and Mr Scott happened about 1am, but detectives were not informed until 8am and the scene was not secured.
The detective who initially handled the investigation did not treat it as a potential homicide and "exercised insufficient care'' with regards to carrying out a scene examination.
"On its face, the initial police investigation appears not to have been formally structured or documented,'' the authority said.
Detective Senior Sergeant Tony Wakelin took over the investigation following Mr Munro's death, but police paperwork related to the investigation could not be found by the authority.
"It is of concern that documentation ... [has] apparently been lost or destroyed,'' the authority said.
"The existence of such material would have been an indicator of a well managed and structured investigation.''
The authority, in identifying shortcomings, also pointed to witnesses who should have been interviewed but were not.
Mr Scott presented himself to police in the days after the fight, but was allowed to leave as the investigation team was not available.
It was another misstep, the authority found.
"That Samuel Scott presented himself and was told someone would contact him the following day is indicative of a failure to appreciate the level of commitment required for this investigation,'' the authority said.
Police reopened the investigation later in 2005, but the reviewing officer, Detective Senior Sergeant Kallum Croudis, was a close working colleague of Det Snr Sgt Wakelin.
That relationship meant he "could not reasonably be considered to be sufficiently independent''.
The review focused on issues raised by Nicholas' father, John Munro, that "should have been addressed properly in the original investigation''.
Despite the "undesirable'' shortcomings in the police investigations into Mr Munro's death, the authority believed the correct decision, not to charge Mr Scott, was made.
"The decision not to prosecute ... was not contrary to law, unreasonable, unjustified or unfair,'' the findings said.
The authority also found no reason to reinvestigate Mr Munro's death.
Southern district commander Superintendent Mike Pannett said police accepted the findings of the authority.
"We note that the IPCA found that the decision not to prosecute Samuel Scott was not contrary to law, unreasonable, unjustified or unfair,'' he said.
"We also note that the IPCA found that there was no justification to recommend a reinvestigation into Mr Munro's death.
"We acknowledge that the loss of Nicholas has been extremely difficult for his family and friends, and we again extend our sympathies to them.''
Police did not wish to comment on the findings of the coroner.
Mr Crerar, in his findings, also criticised the initial police investigation, saying it "should have commenced ... more promptly and progressed ... more diligently''.
He declined to send Nicholas' death back to police for reinvestigation.
"It is now clear that Sam Scott ought not to have responded to the insults and assaults by Nicholas Munro in the manner in which he did,'' Mr Crerar said.
"His reaction was out of proportion to the threat posed to him by Nicholas Munro who was a lot smaller than Sam Scott and was very drunk. The punch which Sam Scott administered was unfortunate in that it had consequences which could not have been anticipated.
"It can be speculated that Sam Scott could have, or should have, responded to the assaults by Nicholas Munro in a lesser manner... A coroner cannot determine 'should have' or 'could have'. Sam Scott responded in the manner which he did.
"Sam Scott remained at the scene ... he spoke to John Munro and ... surrendered himself to the police at the appropriate time, he fully acknowledged his role ... and did not in any way attempt to minimise his involvement.''
Mr Crerar ruled Mr Munro died from cardiac failure caused by his severe head injuries.
Mr Munro was drinking with friends and his sister in the hours before the altercation outside a Frederick St bar, then known as Two Bears.
Mr Munro and Mr Scott traded insults and became involved in a scuffle.
That settled but further verbal barbs led to Mr Munro throwing a flurry of ineffectual punches at Mr Scott.
Mr Scott responded by throwing a punch which rendered Mr Munro unconscious or dazed and disoriented.
Mr Munro fell to the ground heavily, hitting his head on the road. He was taken to Dunedin Hospital by a passing ambulance, where he died five days later.
The coronial inquest was held last November, more than a decade after the incident.