It would be difficult for a gun linked to the deaths of campers Russell Hill and Carol Clay to go off accidentally, forensic police say.

Former airline captain Greg Lynn, 57, has pleaded not guilty to two counts of murder over the deaths of Hill, 74, and Clay, 73, in Victoria’s alpine region and is on trial in the Supreme Court in Melbourne.

It’s alleged Hill and Clay died on March 20, 2020, after an argument between Lynn and Hill at Bucks Camp in Wonnangatta Valley.

Earlier in the trial, Lynn’s barrister Dermot Dann said his client had admitted his involvement in the pair’s accidental deaths.

He said a scuffle broke out after Hill took a gun from Lynn’s vehicle and Clay was accidentally shot by Hill.

The barrister said Hill then came at Lynn with a knife and was accidentally stabbed in the chest as Lynn defended himself.

However, prosecutors allege Lynn intentionally killed Hill and Clay.

Victoria Police officer and ballistics expert Leading Senior Constable Paul Griffiths told the jury about his investigations into projectiles found at the campsite and a gun seized from Lynn’s home.

Griffiths undertook testing on the 12-gauge Barathrum Arms shotgun, taken from Lynn’s home, including a safety function test and trigger pull test.

A trigger pull test measures the amount of force that has to be applied to the trigger to fire a shot.

Lynn’s trigger pull was 3.947 kilograms, slightly above the industry standard of between 1.8 kilograms and 3.6 kilograms.

“Being higher, means have to pull trigger harder to discharge the gun,” Griffiths told the court on Tuesday.

He also tested whether the gun would fire if dropped or if it was overloaded.

“It failed to discharge … which tells me the firearm is in good working order,” he said.

The trial continues.

– AAP