But when a member dies on duty the squabbling is forgotten. And there is nothing more solemn - and touching - than a police funeral at the Academy. The lone piper, the drum horse and the thousands of serving and retired cops who form a silent guard of honour to say goodbye to a fallen colleague.

That was how it was when in August 1998 they farewelled Senior Constable Rod Miller and Sergeant Gary Silk, gunned down in an ambush while on stake-out duty in Cochranes Road, Moorabbin.

Now - nearly 20 years on - that solidarity is crumbling following claim and counter claim into the investigation that ultimately led to the conviction of two men, Bandali Debs and Jason Roberts, for the double murder.

On one side we have former Detective Senior Sergeant Ron Iddles who has completed a review into the Silk-Miller investigation, concluding there are doubts about the validity of Roberts' conviction. (Roberts claims he was not in Cochranes Road and did not take part in the ambush.)

Iddles is perhaps Australia's best-known homicide detective - the subject of a top-selling book and soon-to-be-released two-part documentary. Iddles has concluded: "On the basis of probability, he [Roberts] was not there." He knows to be seen to side with a convicted cop killer will make him enemies in the job he loves. He told 3AW's Neil Mitchell: "I didn't ask to do this. I put my head on the chopping block by being honest, having integrity and doing it without fear or favour. The guillotine will come down and I'll be blamed for this. [People are saying], 'Ron's a rogue, Ron's gone off the rails'."

There is no doubt that Iddles' stand is brave. But is he right?

On the other side is Detective Superintendent Paul Sheridan, a former homicide colleague of Iddles and a graduate of the FBI Academy, who headed the Lorimer Taskforce - the investigation in the Silk-Miller murders. Sheridan is a stickler for procedure, refuses to cut corners, is determined sometimes to the point of stubbornness and has a force-wide reputation for honesty. Like Iddles he now feels his integrity is being questioned.

Briefly, the background. In 1998 there were 10 armed robberies involving a middle-aged and younger offender who were targeting suburban restaurants. As a result the Armed Robbery Squad set up Operation Hamada that identified a list of 60 possible targets - with a plan to stake out the restaurants and catch the bandits in the act.

The Silky Emperor on Warrigal Road was in the top 10 - and it was while on stake-out duty that Gary Silk and Rod Miller were murdered.

As a schoolboy, Gary knew he would be a policeman and he lived within sight of the Police Academy. He joined at 21 and was a natural.

At his wake a colleague talked of going out on the town with "Silky" hoping to meet girls (Gary referred to such nights as "Chasing Princesses" ). As a bachelor living alone, Gary was never too fussed on what he wore and so his mate was relieved that night to see he was wearing a pair of jeans and a shirt.

Later at a nightclub his police mate was talking to a girl who expressed concern at Gary's attire (as he was making a rare sojourn to the dance floor). It was only then he noticed that Silky was wearing a pair of rented ten-pin bowling shoes - complete with the No.9 on the back.

Rod Miller was deeply in love with his wife Carmel, who had just had their baby son. Before the stake-out shift the couple completed thank you notes to the 90 friends and relatives who had sent cards welcoming the birth of their boy James. By the time the cards arrived Rod was dead.

The case that would be eventually be put to a Supreme Court jury was that after spotting a suspect car near the restaurant turning in Cochranes Road, Miller activated the portable blue light in the unmarked police car. Silk, the senior man, pulled in behind the dark Hyundai.

Debs, the driver, hopped out and stood next to the door and was approached by Miller. Silk called on Roberts to get out of the car to a grassy verge on the side of the road. Both police had their guns holstered. Silk stood about a metre from Roberts when Miller headed to the police car to radio in the details of the Hyundai. Roberts fired from point-blank range with his .38 revolver, shooting Silk in the chest. Miller, caught between the two cars and lacking immediate cover, unbuttoned his revolver and fired at Roberts, but Debs dived back into the car, grabbed his .357 Magnum and fired repeatedly through the rear hatch, shattering the glass and hitting Miller in the chest.

But here is the sticking point. Another police unit saw the suspect car and only saw the driver in the vehicle. Lorimer detectives say this was because Roberts was hiding in the passenger well.

In Iddles' subsequent review he argues there is no evidence to support the two gunmen case and the facts have been massaged to fit the theory.

The Crown case is supported by claims from police who found the fatally wounded Rod Miller, who say their dying colleague said: "Two. One on foot ??? dark Hyundai ??? I'm f----d, I'm f----d ??? I'm having trouble breathing ??? get them."

One of those present was Senior Constable Glenn Pullin. This week the Herald Sun revealed Pullin did not mention those words in his first statement but a version of Miller's observation was later inserted and backdated.

Iddles says this is proof of corruption and that evidence was concealed from the defence.

What should have happened is that if Pullin's statement was to be updated, it should have appeared as a new document and not presented as the original. The claim a Lorimer investigator doctored documents is now the subject of an IBAC investigation.

The statements of other police at the scene were updated with Miller's words. As Iddles says: "Beware of the witness whose memory improves with the passage of time."

So does this mean that Debs acted alone and Miller did not say there was a second offender? Certainly the scene was chaotic but police tapes show that at 12.32am Cheltenham 206 reported a "Member shot twice . . . He said two offenders, two on foot."

The then head of the Armed Robbery Squad, Detective Senior Sergeant Ray Watson, told The Age: "Two offenders were mentioned from the beginning."

The most compelling evidence of two gunmen (the police were shot with two firearms) comes not from the scene but 18 moths later through Debs' bugged conversations with his father where he appears to recall the shooting.

"Those were the ones [Silk/Miller] that were sittin' there, when we drove in just to quickly look [at the restaurant], they seen us so they drove behind us, and drove down the street to stop us, they stopped us. Then it's not good. . . . Cause we heard it on this, we heard it on that, they said oh one is gone [Silk] we can't find the other one [Miller]. After we left they come in 30 or 40 seconds. Thirty or 40 seconds they were there, that means they had a few [police] cars in the area."

And there was another damning statement - this time by Roberts who bragged, "I kill Ds" - words the prosecution claimed meant detectives or police.

Roberts' first attempt for a review was rebuffed. His lawyers approached then Chief Commissioner Simon Overland looking for a deal. In exchange for information implicating Debs in cold case murders he wanted his case reviewed. Overland's response was short and Anglo Saxon.

If Roberts had information he could provide it, and if it panned out police may support a move to reduce sentence. The offer was rebuffed with equally blunt language by his lawyers. Years later a similar file ended with Iddles in circumstances that remain unclear.

Regardless of personalities, the investigation should not have stayed with him for as a senior sergeant he was not in a position to interview Superintendent Sheridan - a superior officer and former squad mate. (Sheridan was not initially given the chance to respond to the Iddles report - a fact that irks many of his colleagues).

The investigation should have been handed to a senior officer with homicide experience, or even better an interstate team to avoid claims of bias.

What we do know is Debs and Roberts committed 10 previous armed robberies as a team and there is no known reason why Debs went to the Silky Emperor that night on his own armed with two guns.

Regardless, Roberts is the victim of an injustice. He was sentenced to life with a minimum of 35 years. But the law has been retrospectively changed to ban convicted police killers from applying for parole. Which means his papers are now marked never to be released.