The case was doomed from the start.

What should have been the high watermark of investigations ended in recriminations, acquittals and no justice for two police murdered on duty.

Constables Steven Tynan and Damian Eyre were gunned down in Walsh Street, South Yarra, in 1988.Credit: The Age

From the crime scene to the offices of senior police, a series of mistakes compounded by a raft of decisions that were plainly bizarre, left the detectives handling the case hopelessly handicapped.

This is not rearview wisdom – many of those in the middle saw the slow-motion collapse, like the implosion of a building being demolished.

Yet from within the rubble was a gold nugget – a criminal informer who left a tip that years later would lead to solving an unrelated professional hit – but more of that later.

First, the original crime: on October 12, 1988, on Walsh Street, South Yarra, two Prahran police constables, Steven Tynan and Damian Eyre, were checking an abandoned stolen car when they were ambushed and shot dead.

On March 26, 1991, 895 days after the murders, four men – Victor Peirce, Peter McEvoy, Anthony Farrell and Trevor Pettingill – were acquitted by a Supreme Court jury. They maintained their innocence.

It began at the crime scene. In a confidential review written by taskforce leader Detective Inspector John Noonan, and obtained by The Age, he wrote: “Crime scene was cordoned off by crime scene tape. However, this was disregarded by most police members and by members of the public.

“The crime scene was severely contaminated, understandably by police and ambulance in assisting injured members, but later by persons disregarding general crime scene instructions.”

Emotions were running high, mistakes can be made, but there was a school of thought among some senior police that would underpin a series of decisions that were dumb then and remain dumb now.

Noonan believes the initial view was that the murder of two police officers should be treated as any other double murder, failing to acknowledge that such an ambush was an attack on law and order, and by extension on society itself.

Does anyone seriously think the assassination of a prime minister would be assigned the same resources as any other murder?

It was a full two weeks before the Ty-Eyre taskforce was established, and when it was, it was sent to the 13th floor of the St Kilda Road........

© The Age