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A bike helmet allegedly left outside the Ashburton Work and Income double-murder scene by a fleeing gunman had DNA with "extremely strong" scientific evidence linking it to accused shooter Russell John Tully, a court heard today.
Tully's double-murder trial at the High Court in Christchurch has previously heard that the fleeing gunman left behind a bike helmet and bike lock outside the Cass St Winz centre.
On day seven of the trial, ESR forensic scientist and experienced DNA analysis expert Lisa Melia told the jury that she was given DNA samples taken from the strap and inner fabric from a black bike helmet recovered from the scene.
Her laboratory testing concluded that the DNA sample corresponded with Tully's DNA profile, the court heard.
It was "five million million" times more likely that it came from Tully instead of another person selected at random from the general New Zealand population, the scientist said.
The results fell into the highest category of DNA profiling, she said, with "extremely strong scientific support" that it was DNA originating from Tully.
Tully, 49, denies being the masked gunman who murdered receptionist Peggy Noble, 67, and case manager Susan Leigh Cleveland, 55, inside the Winz office on September 4, 2010.
He also denies attempting to murder two fellow workers Lindy Curtis and Kim Elizabeth Adams and other charges that include two counts of unlawful possession of firearms, and one of setting a mantrap.
Identification of the masked gunman is key to the trial, the jury has heard.
The Crown says evidence that the shooter is Tully is "overwhelming".
Earlier today, the court heard that two shotgun cartridges allegedly found wrapped in a sock during Tully's arrest hours after the shooting spree were the same brand as a spent shell casing found at the murder scene and matched pellets fatally blasted into Ms Noble.
Six shots were fired from a pump-action shotgun by a balaclava-clad intruder.
Five of the six shotgun cartridges were removed from the scene and later examined by Institute of Environmental Science and Research (ESR) scientist Gerhard Weavers, the trial heard this morning.
One spent cartridge had a black "inX" sticker on its exterior wall, matching the inX signature that the Crown says Tully used to label his possessions.
Mr Weavers also examined a semi-automatic shotgun labelled with three inX stickers allegedly found in Tully's possession on September 1, 2014. The ESR scientist was told it was not the murder weapon.
He also examined 37 shotgun cartridges recovered in a sock allegedly found in Tully's possession, the court heard.
In most cases, the markings on the cartridges had faded, Mr Weavers said.
However, each one of four brands recovered had a black inX sticker attached to it, the jury was told.
And Mr Weavers said that two of the shotgun cartridges were Kent brand with size-4 lead pellets -- allegedly matching a spent cartridge found inside the Winz office.
The other 35 cartridges were different to what were present at the murder scene, the court heard.
However, pellets found in Ms Noble's medical examination kit also came from a Kent brand size-4 cartridge case.
Tully, who has twice been removed from court after outbursts before the jury, is not present in court today.
He is not be represented in court by his own defence counsel. Instead he is legally assisted by two amicus, or friends of the court, lawyers Phil Shamy and James Rapley.
The trial, before Justice Cameron Mander, continues.