"There's now a mandatory meeting between the defendant's lawyer and a police prosecutor to discuss the charges and see whether there's any room for movement," he said.
"The fact that there are changes being made to the charges - which often happens at a case manager's meeting - is the system, and that's what it was designed to promote," Mr Nabney said.
He said the meetings indicated to a defence lawyer or prosecutor their chance of success should a case go to trial - and whether parties should make concessions.
Police Association president Greg O'Connor said higher success rates in court were due to fewer low-level offenders being prosecuted - instead being given pre-charge warnings.
In 2011, the Ministry of Justice announced a target of reducing crime by 15 per cent by 2017. Since 2011, prosecution and conviction numbers nationwide have dropped 28 per cent and 27 per cent respectively.
"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 fewer people offending or that there's less lower level offending taking place."
He said offenders were realising low-level crimes would often go unpunished.
"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."
Mr O'Connor said he was unsure how the long-term effects of pre-charge warnings would balance out against the short-term benefits.
"If you are the Government and want to put out press releases that say the number of arrests have gone down and the number of court appearances have gone down, then yes it's a great policy.
Sensible Sentencing Trust Tauranga spokesman Ken Evans said if a person had broken the law then they should face penalties for their actions.
"It doesn't serve a lot of purpose to let people off, congratulations to the local police for seeing that as a way to stop crime rather than being soft with people.
"If you are firm at the beginning, hopefully it will stop a life or cycle of crime for somebody."