UPDATED: 5.20PM The jury in the High Court trial of double murder-accused Russell John Tully has spent the morning hearing from a firearms expert.

Forty-nine-year-old Tully is once again not present in the court room.

This morning's proceedings got underway late, because of arguments in closed court.

Gerhard Weavers analysed CCTV footage of the shooting, which he said shows a shotgun shortened so its pellets would have maximum impact.

"A barrel which has been shortened and unchoked will spread very quickly compared compared to a full length choke barrel," he told the court.

Weavers said that one of the shotgun cartridges found at the WINZ office, had an I-N-X sticker on it.

The Crown said those stickers were used by Tully to mark his property.

Mr Weavers also examined a semi-automatic shotgun labelled with three I-N-X stickers allegedly found in Tully's possession on September 1, 2014.

The ESR scientist was told it was not the murder weapon.

ESR forensic scientist Lisa Melia said DNA found on a helmet after the shootings was five million million times more likely to have come from Tully, than anyone else.

But lawyer James Rapley, who's acting as an amicus assisting Tully, questioned how she could be certain how the DNA got there.

An earlier witness in the trial reported seeing the helmet fall off the gunman, as he rode away from the shootings in September 2014.

HANDWRITING

A handwriting expert is all but certain Tully was the author of a note with the names of the Ashburton Work and Income staff.

Tully was found in possession of the note which contained the words, Adams, Cleveland and discrimination, when he was arrested near an Ashburton farm on the day of the shooting.

Police senior document examiner Jessica Owen compared the note with other documents written by Tully and said they’re the same.

"None of the limitations that can sometimes appear were present so this was my strongest level of opinion."

Kim Adams and Leigh Cleveland are both case managers Tully dealt with frequently.

The crown said the note proves intent.

The trial continues.