Mr Krebs said police prosecutors and defence lawyers were now able to communicate more before a trial.
"There is a greater focus on resolving things prior to a defended hearing, and there's an encouragement for plea negotiations," he said. "I think even the courts are encouraging resolving things through negotiation and pleas."
Mr Krebs said lawyers, judges and courts have "embraced" new procedures which encourage negotiation between parties.
Police prosecuted and convicted fewer people in the region's courts last year than any year since at least 1980. Both figures have fallen for the last six years.
Police association president Greg O'Connor agreed the greater use of warnings for low-level offences had led to higher conviction percentages. However, he said prosecuting fewer people wasn't necessarily the best policy.
"Police have way overshot," Mr O'Connor said. "I don't think anyone believes the behaviour on the street has improved at all. I don't think anybody believes there are less people offending or that there's less lower level offending taking place."
In 2011, the Ministry of Justice announced a target of reducing crime 15 per cent by 2017. Since then, nationwide prosecution and conviction numbers have dropped 28 per cent and 27 per cent respectively.
He said offenders were realising low-level crimes would often go unpunished and may result in a future crime boom.
"One of the problems is now you have a generation of people who have grown up understanding that actually there are no real consequences for a lot of behaviours, other than the inconvenience of being dragged back to a police station and kicked out an hour later," Mr O'Connor said.
"They have no fear of the system."
He was unsure how the long-term effects of pre-charge warnings would balance out against the short-term benefits.NZME