Robin Bain more likely than not shot himself, and he could have done it with ease, an expert has told the High Court at Christchurch.

British firearms and ballistics expert Philip Boyce yesterday demonstrated to the jury in the Bain murder trial several ways in which Robin Bain, 58, could have used the rifle found next to his body to commit suicide.

His finding was that the rifle was pressed against Robin's temple, or very close to it, when it was fired, causing a "contact or near contact wound". Yet it was also possible suicide occurred with the rifle up to 22cm away from the head.

"The results of my tests are that it is quite easy to shoot yourself with that rifle."

Mr Boyce was giving evidence for the defence in the trial of David Bain, 37, who is charged with shooting dead his parents and three siblings in their Dunedin home on June 20, 1994. Bain's lawyers say his father, Robin, killed the family and then shot himself.

Three prosecution experts have said the rifle would have been about 20cm or more away from Robin's head when fired, making suicide unlikely or impossible.

But Mr Boyce's evidence has now called those contentions into question.

He calculated that Robin theoretically could have pulled the trigger on himself with the rifle "somewhere between 18 and 22cm" from his head.

The jury asked Mr Boyce whether Robin's blood would be expected on the rifle silencer if it had been a contact or near-contact wound. Mr Boyce said it would.

Blood from Robin's son Stephen Bain, 14, was found on the silencer, after Stephen fought his killer, but no blood has been confirmed as belonging to Robin. The defence says some blood on the silencer went untested.

Mr Boyce was sent several items, including the rifle, a skullcap and steel rod showing the path of the bullet travelling through Robin's head, and pictures of Robin's fatal wound, in order to do his own analysis.

Asked about the likelihood that Robin committed suicide, Mr Boyce replied: "I would say more likely than not."

Questioned by prosecutor Robin Bates, Mr Boyce agreed a close contact wound to Robin did not rule out murder. He agreed with Mr Bates that had Robin been intent on committing suicide, other simpler options would have been open to him, such as shooting himself in the mouth or under the chin.

Robin's daughter Laniet, 18, was found dead in her bed with three gunshot wounds.

The prosecution says the first shot was to her cheek, allowing David Bain to hear her gurgle, before two further shots above the ear and on top of the head.

Mr Boyce said his view was that the first shot was to the top of Laniet's head, and she must have been moved for this shot to have occurred.

The court also heard yesterday from meter reader Darren Palmer that Robin wanted a final reading at the school house where he was living the month of the killings.