"That's managed to take about a million guns out of civilian arsenal. [As a] consequence of this gun deaths dropped by about 50 per cent and stayed around there.
"We've got 1.1 million firearm licenses in New Zealand, for 230,000 licensed firearm users. I think it would be very helpful if we had a buy-back programme or even an amnesty where people could give their old guns back and have them destroyed and take them out of circulation."
Preventing registered guns from falling into the hands of known offenders or gangs was an issue, he said.
This could be prevented by reducing the total number of guns in circulation and ensuring they are registered to specific owners.
This way, any gun used for criminal activity could be "identified and sourced back", Professor Clements said.
Yesterday, armed police were sent to Main St in Upper hutt after receiving reports of a man with a firearm outside McDonald's.
The man aimed the firearm at officers and was shot, a police statement said. He died a short time later despite immediate medical attention.
Officers were still working to establish exactly what had happened and were speaking to a large number of witnesses, police said yesterday.