The eight grooves on a 1.849g bullet fragment provide microscopic proof that it was highly likely fired from a rifle owned by murder-accused Quinton Winders, the crown says.

Detective Senior Sergeant Edward Schey, head of the forensic ballistics section of the New South Wales police, says the grooves, along with the land marks - akin to a rifle bore's tattoo - allowed forensic staff to find similar matches of bullets.

Schey took the stand in the Rotorua High Court today in the trial of Winders who is charged with the murder of stop-go worker George Taiaroa on March 19, 2013.

Schey has talked the jury through the microscopic detail left by the fragment - one of three - taken from Taiaroa after he was shot.


The crown has been unable to find the murder weapon. However, they have found rifles they say are made from the same batch as Winders - a match made by their serial numbers.

Schey says when the bullet is fired from the rifle's bore, they can use the bullet's weight, rifling and diameter to help refine which type of firearm the bullet was fired from.

Given how the fragments have splayed upon impact, he said the rifle must have been fired on a perpendicular angle - 90 degrees.

"The portion of the front [of the bullet] rolls back on itself and peels off behind it ... if it strikes at an angle it won't do it."

He told the jury although police recovered three fragments from Taiaroa there was only one - the largest - which provided enough detail to gather information.

"The single bullet fragmented into three pieces, possibly more ... with the larger piece it contains the majority of the land and grooves ...on impact it has squashed and folded."

The weight of the bullet helped his team narrow down the calibre of the rifle used - a .22.

There was a portion of the base of the large fragment that measured 6.37mm that aligned with coming from the .22.

Those calibre rifles use bullets that range between 2.332g and 2.592g in weight, he said.

He was given test fire samples from police and magnified the land and grooves left on the bullet to match them to another rifle.

The engraved marks, or groove marks, are the most revealing and run perpendicular to the bore and create the individual characteristics on fired bullets.

Meanwhile, Justice Kit Toogood advised the jury the trial will extend into a fifth week due to the time taken so far.