There is a possibility Samuel Richard Scott had a manslaughter case to answer but police blunders in the investigation put paid to justice, legal expert Mark Henaghan says.
Mr Scott threw the punch which led to Dunedin teenager Nicholas Munro falling backwards and slamming his head on to the tarseal of Frederick St early on March 6, 2005.
Five days later, Mr Munro (18) died in Dunedin Hospital from complications stemming from his head injuries.
Mr Scott was never charged in relation to the incident.
Earlier this week, coroner David Crerar released his findings on Mr Munro's death, siding with the police and crown prosecutor's decision not to lay charges, but labelling Mr Scott's punch "out of proportion''.
It is that phrase which causes unease for the University of Otago dean of law.
"There seems to be a reasonably clear finding that the force used by [Mr Scott] was ... out of proportion and excessive force,'' Prof Henaghan said.
"If you use excessive force and it results in a criminal act, you can be charged.
"It's not a question of whether you intended to harm him. It's whether you used excessive force and it resulted in harm.''
The incident was clearly not a case of murder, but manslaughter charges could have followed, he said.
"Manslaughter just requires an act to be unlawful,'' Prof Henaghan said.
"If it was excessive force, then it's an unlawful act.''
The difficulty lay in proving excessive force was used and the initial police response had severely hampered proving that, he said.
"The real problem with the police inquiry, and the coroner rightly observed, was that the evidence gathering wasn't done as well as it should,'' he said.
"I think the investigation is where it fell down here and, in a situation where someone dies, you should always have a thorough investigation.
"When the police themselves and the coroner say it wasn't done properly, that does raise concerns.''
The failings in the early response and first investigation gave an insight into why the crown prosecutor might not have had a thirst to pursue a prosecution as poor evidence gathering could impact the likelihood of securing a conviction, he said.
"I do think this clearly wasn't good enough,'' Prof Henaghan said.
"Given the circumstances, it was reasonable to not go ahead [with a prosecution] but I don't think that's good enough. The decision made some sense but the problem stems from [police] not doing their job properly.''
He described Mr Munro's death as a "catastrophe'' and acknowledged his father's appetite for justice.
However, the possibility of any sort of criminal proceeding seemed remote now as almost 11 years had passed, he said.
"You have to feel great sympathy for the father in this case. His instincts are it's got to be excessive force and there is evidence here that indicates that.''
Mr Scott's name was publicly released on Monday for the first time in the decade that followed the incident after the coroner released his findings.
Mr Scott had sought an order preventing publication of his name, but Mr Crerar declined that order.
"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 in his findings.
"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.''
