He said it was his opinion that all the injuries could be explained by one shotgun discharge, but he could not exclude two or even three discharges.
ESR forensic firearms expert Kevan Walsh told the court today he examined the the crime scene in the two days after Mr Guy was shot dead.
He explained to the jury about how shotgun cartridges were made and how they worked when they were fired.
Mr Walsh said the shells had a case that held all the components within it, starting with a primer.
Depressing the shotgun trigger struck the primer, which ignited the propellent.
That caused rapidly expanding gas to propel a plastic wad and lead shotgun pellets down the barrel of the gun at high velocity.
The wad and pellets separated from each other as the distance they travelled from the barrel increased.
Mr Walsh said shotgun shells could have a large number of small lead pellets or a small number of large pellets.
He said there was no way of determining whether or not pellets had been fired from a particular shotgun.
Mr Walsh said the wad could be marked as it passed down the barrel, but generally because of the smooth nature of the shotgun barrel, the wad could not be linked to a particular gun.
The exception was sawn-off shotguns which had some damage at the end of the barrel that marked the wad.
Mr Walsh said the design of the wad could be an indicator of the brand or manufacturer of the ammunition.
Police armourer Robert Ngamoki gave evidence today on his examination of the 12-gauge double-barrel shotgun from the Guy family farm.
Mr Ngamoki measured the trigger pressure and performed a trigger test to see if the gun could fire accidentally.
"It is safe, you need to press the trigger to discharge it," he told the court.
He said the safety catch and barrel selector were working.
Mr Ngamoki test fired the gun and found it was capable of discharging a shot of Winchester ammunition.
He said the shotgun had a choke mechanism that allowed the shooter to control how closely the pellets stayed together at distance when discharged.
The shotgun cartridges had to be extracted rather than expelled from the gun.
Under cross-examination by defence lawyer Greg King, he said it was a possibility the cartridges would fall out of the gun once its barrel was opened. He would not say it was a probability.
Mr Ngamoki said there was surface rusting and some minor residue on the barrel, probably from inadequate cleaning.
He agreed it had the appearance of a typical farm gun.
Mr Walsh's evidence is continuing.
