The intricacies of a rifle's serial number and production history helped a firearms forensic scientist match, what he believes, is the same firearm owned by murder accused Quinton Winders.
New South Wales police forensic ballistics investigator Walter Murphy talked the jury through the elaborate process he took to come to his conclusions in the High Court at Rotorua today.
Murphy told the jury that he was first contacted in March 2015 by police investigating the death of stop-go worker George Taiaroa on March 19, 2013 who was killed by a single shot to the head as he stood at the road works site on Tram Rd.
The crown allege that it was a bullet fired from a weapon that Winders was registered as owning when he went for his firearms licence in 2008.
The crown say it's the grooves left in the bullet fragments which match that coming from a .22 Winchester cooey bolt action rifle - and more specifically - one owned by Winders.
However, the murder weapon has never been found.
When police searched his house after the murder, Winders claimed the two .22's were stolen in a burglary in 2009.
Giving his testimony, Murphy explained how he microscopically analyses firearms to help trace their history.
He said he was quickly able to establish the rifle with the serial number 022336 - the alleged murder weapon registered to Winders - was first imported into Australia, from Canada, on July 28, 1971.
It was then on-sold to Dunlop Sports in Auckland in October 6, 1971.
In their investigation, police asked Murphy to work out if the signature marks in the batch of firearms produced at that time matched that of Winders' .22.
Murphy told the court that the .22 firearm registered to Winders is from the same batch as another .22 Winchester firearm uncovered by police with the serial number 022339.
Murphy told the court it not only had the same shipment details but after analysing its serial number, they also had the same format and distinguishing features including marks from when it was pressed into the metal. He also created 3D castings of the serial numbers and microscopically analysed the indentations made by the stamping tool in the manufacture process.
He said he also found another batch of .22 Winchester rifles, he testified, that were produced with the same stamp stool during the rifle's manufacturer in Canada.
Earlier in the day, ESR forensic scientist Kevan Walsh gave evidence that the firearm used in the shooting could have been fired from as close range as 300mm, slightly closer than the 500mm as told by forensic pathologist Dr Simon Stables on Tuesday.
Walsh carried out a forensic examination of the murder scene the day after Taiaroa was shot and said he did not uncover any other DNA evidence belonging to anybody else.
However, he did modify his position on the type of bullet of used. Rather than being a "solid" bullet, he accepted it could also have been a "hollow" bullet.
His "best estimate" of the bullet's weight was 2.46 grams.
The trial continues.