Masterton lawyer Frank Minehan said the threshold for qualifying for a discharge without conviction was high.
And while the diversion scheme had been in place for "a long while", it could be playing a role in reducing the number of discharges given out.
"First time offenders, particularly young people, have the opportunity to [get diversion] and I think it mops up a reasonable number of people."
The number of people discharged without conviction nationally also dropped from 3185 in 2011 to 2720 in 2012, to 2199 last year.
Last month, Maori King Tuheitia's son, Korotangi Paki, 19, made headlines when he was let off charges of burglary, theft and drink driving after his defence counsel successfully argued a conviction would ruin his chances of succeeding to the throne.
In the High Court in Auckland last week [9/8], Justice Helen Winkelmann decided not to convict the teen who assaulted 15-year-old West Auckland schoolboy Stephen Dudley before his death on June 6 last year.
Sensible Sentencing Trust national spokeswoman Ruth Money said while the number had come down, more discharges were being granted for "inappropriate" crimes such as assault and drink driving causing injury.
"Frequently we have victims coming through to us saying 'I was the victim in this case, how could this happen? We are certainly being overwhelmed with what we would classify as unwarranted discharges."