Chief Police Officer Rudi Lammers' extraordinary decision to engage one of the country's leading crash investigators to re-examine Mr Forsyth's death could, in time, see it referred to a cold case homicide team with a view to a potential prosecution.

Mr Forsyth was mowed down by a blue panel van and left to die on Kent Street in Deakin in the early hours of the morning of March 1, as he walked away from an 18th birthday party with friends.

Serious irregularities in the initial police probe were uncovered during a lengthy investigation by Fairfax Media in 2013.

Strangely, the death was not handed to homicide detectives and suspicious circumstances were ruled out almost immediately, despite evidence at the time suggesting the van had veered towards Mr Forsyth after a threat on his life was made at the party.

New allegations surfaced in 2013 that police bullied one of Mr Forsyth's friends into staying quiet about a confrontation he had with a panel van driver about the death.

That driver had been at the party and was pulled over trying to drive back past the scene, but a lone officer allowed him to leave because his car was the "wrong colour".

There were clear contradictions in the evidence of that van's driver and its passengers about their movements and reasons for driving back to Kent Street.

Errors in forensic analysis left police searching for the wrong-coloured panel van for months, and the vehicle pulled over near the scene was never re-tested once the mistake was realised.

Mr Forsyth's mother, Valerie Tomkins, who passed away this year, and sister Vanessa Forsyth have long battled for the truth and criticised an investigation marred by errors. Their concerns were such that they believed there may have been a deliberate cover-up.

In revealing his decision to review the case, Assistant Commissioner Lammers said he was determined to get to the truth once and for all.

The police chief took a close personal interest in the case, following Fairfax Media reports and a letter from the family's barrister, Bernard Collaery, who had asked for ACT Policing to apologise.

That involved him personally combing through vast volumes of evidence and speaking with past and current investigators, many of whom said they still had a "nagging doubt" about the case.

"It's not common for the chief police officer to be involved in this way," he said. "But I was significantly persuaded by what I had read that there was a need for me to be involved personally and make some decisions ... it was a decision that only I could make."

The highly experienced independent crash analyst, John Ruller, has already begun his work.

He was deliberately chosen to alleviate any concern about police investigating police.

His review is being funded by ACT Policing, at no small cost, and he will be afforded full access to the Australian Federal Police's resources, including intelligence systems and forensic capabilities.

Mr Ruller will review the evidence using modern and vastly improved crash investigation techniques.

He will make one of several recommendations to the police chief; either that everything that could have been done was done, that there were flaws but they cannot now be remedied, or that things were missed that can still be followed up.

A critical issue will be whether the early investigation should have been handed to homicide detectives instead of the poorly-resourced accident squad, something that would have completely reshaped how it was handled.

Asked whether that decision was jarring, Assistant Commissioner Lammers said: "Yeah, absolutely. One of the things I was concerned about and one of the things that I really wanted to know ... was exactly why a decision was made or wasn't made to treat it as a homicide.

"If it ought to have been deemed a homicide, then certain things should have been done in line with criminal investigative practices, and I need to know whether or not there is still scope to examine those now."

The loss of forensic exhibits in a flood at the old evidence management centre would hamper the re-examination, but not impossibly so.

The announcement has come too late for Mr Forsyth's mother, Ms Tomkins, who died after a long battle with cancer earlier this year.

But the news has been praised by Mr Forsyth's sister, who is determined to get the truth but is realistic about the hope of a prosecution 28 years on.

"I'm absolutely overwhelmed and absolutely excited, relieved, and I'm just hoping some kind of justice will come from this. I'm just speechless, really," Ms Forsyth said.

"I'm not in denial, I really don't think that the person who was at fault will be caught. I don't think that will happen. But what I want to happen is to see a full investigation."

Assistant Commissioner Lammers said he was sorry and disappointed that Ms Tomkins had passed away before the announcement.

But he said he needed to take the time to go over the complex volumes of evidence properly before going to the family and potentially giving false hope.

"It's unfortunate that it's taken this long, but I wanted to do this thoroughly.

"To read everything through, to understand it, to comprehend it, and then in your mind to start joining things together takes a considerable amount of time."