Constable Crews, 26, was accidentally killed by a police colleague during a gun fight with a drug dealer in a basement car park in September 2010.

In handing down his findings into the incident, Coroner Michael Barnes said the tragedy had highlighted errors by individual officers as well as broader systemic failures regarding operational risk assessment and the way plainclothes officers identified themselves.

"On occasions, police are forced to rush into dangerous situations - this was not such a case," Mr Barnes said on Monday, as Constable Crews' family and police mates looked on.

"There was no pressing urgency that demanded such a response. No one undertook sufficiently careful and considered analysis as to what needed to be done and to how it could most safely be done.

"These shortcoming contributed to an emergency arising in which a mistake was more likely to happen. Tragically, in this case, that mistake was fatal."

Mr Barnes said that, when Constable Crews and his colleagues from the Middle Eastern Organised Crime Squad (MEOCS) entered the car park in Bankstown to execute a search warrant, they mistakenly believed that the target, drug dealer Philip Nguyen, was unlikely to be armed and represented a low risk.

This was based solely on information that an informant, known as "X", had given to the officers leading the operation, Detective David Roberts and Senior Constable Richard McNally, rather than any physical surveillance of Nguyen or the premises.

As a result, none of the officers involved in the raid knew that Nguyen was armed with a Glock pistol and had been the target of an attack by rival drug dealers just weeks before, leaving him extremely anxious about another attack.

When the officers eventually reached the garage where the drugs were meant to be hidden, having made a number of errors about the exact location of the garage and how to get there, Nguyen ran from behind a silver sedan and fired at them.

In the ensuing confusion, Detective Roberts fired a shot with one hand that struck Constable Crews in the back of the neck, fatally wounding him.

Mr Barnes found that the officer had not been looking in Nguyen's direction when he fired and had not discharged his weapon according to police procedure, which requires officers to have two hands on the weapon when firing and to face the target.

Crucially, the officers were not clearly identifiable as police during the operation, which the coroner described as "a dangerous error".

"Mistaken identity was a likely factor in Mr Nguyen's decision to shoot," Mr Barnes said.

"They didn't look like police officers; they looked like robbers. I don't think Mr Nguyen would have tried to shoot his way out had he realised they were police."

The coroner said that, at the time, police policy had been unclear as to precisely how officers should identify themselves in such situations, though this had now been addressed through a new "operational order".

The coroner also found that there had been a series of errors ascending up the police hierarchy in relation to the risk assessment process carried out before the operation, which categorised the operation as "low risk".

Not only had Constable McNally completed the assessment without sufficient intelligence, he had made an error on the risk assessment form.

These errors were not picked up by any of the more senior police officers responsible for supervising the operation, including Detective Roberts, Detective Inspector Mark Ryan from MEOCS or the Commander of MEOCS Detective Superintendent Deborah Wallace.

The coroner found that Inspector Ryan had approved the operation "without proper scrutiny of the details" and "without proper consideration as to the potential risks involved".

However, he noted that the senior officer had not been able to view the final orders because his smart phone had been withdrawn due to funding cuts.

Mr Barnes found that Inspector Wallace had made an "unwarranted assumption" about the effectiveness of X as a source and described her failure to formally approve the raid because of a flat mobile phone battery as "somewhat lax".

He found that, in the five years since the incident, the NSW Police Force had "rigorously engaged with each of the inadequacies highlighted by the circumstances in which Constable Crews died".

"These criticisms must be tempered by acknowledging that they occurred because the officers involved were so committed to their mission they allowed a degree of indiscipline and hastiness to override circumspection," Mr Barnes said.

"They were doing what they had sworn to do - protect the public. Sadly, one of them died doing it."

Nguyen, 58, pleaded guilty to manslaughter and was jailed for a minimum of 12 years in 2013, following an appeal by the Director of Public Prosecutions. His sentence for shooting with intent to cause grievous bodily harm was increased from four years' minimum to six.