Speaking to delegates at the annual meeting of New Zealand Blue Light, a police-community youth policing programme, Judge Becroft said child and youth apprehensions peaked in 1996 and the 2006-07 statistics were the lowest since record-collection started.
"Since then [1996], they have steadily decreased overall - you never hear that [in the media].
"Even my mum says `Andrew, what are you doing with the skyrocketing youth crime rate?'.
"You never read [that they're decreasing] in the papers."
Judge Becroft said property offences were also decreasing, with the lowest number recorded in 2007.
"All the groups [figures] are coming down, except violence, and that ought to concern us, because that's what dominates the media.
"All age groups are showing an increase in violence - it's not just a youth thing."
Judge Becroft said statistically, the 51-99 year age group showed the largest percentage increase in violence in the past five years, while the group with the lowest rise was 12-13-year-olds.
Judge Becroft said New Zealand's police youth aid service was the best in the world, a claim proved by the fact more than 80% of diverted offenders never reoffended.
"We have got to treat every young person we're dealing with as if they are salvageable."
However, not all were salvageable, with some described by Judge Becroft as "unexploded human time-bombs".
The majority of youth offenders in New Zealand - about 80% - fitted into the "adolescent onset" category.
Offenders in that category usually only offended as teenagers and "the good news is, we can work with that group really well and we need to continue doing it".
The other group, estimated at 5% of youth offenders, numbered between 1000 and 2000 in New Zealand - "a small group that really challenge us".
"When you look at it as numbers, it's much more manageable.
"We know who [the 5%] are, we know in New Zealand who the most serious group is . . . it's a small group of unexploded human time bombs."
Judge Becroft said it was almost impossible to pinpoint the cause of violence - while alcohol, cannabis, family and early violence all played a part, it was difficult to know "which one was the trigger".
Howeverit was more important to talk about "risk and resiliency".
"Rather than saying these are the causes, when young people have a group of risks . . . the more likely the offending."
Blue Light Ventures Inc national manager Brendon Crompton said 145 delegates, including sworn police officers, truancy officers, Child Youth and Family representatives, youth aid workers, Ministry of Social Development representatives, Lions and Rotary members, judges and delegates from Australia and the Cook Islands, were in Queenstown for the conference.
Blue Light was a youth policing programme run proactively in communities, designed to help build positive relationships between the police and young people.
It encouraged "healthy socialisation events and activities", with more than 60 different programmes run in 67 branches across New Zealand.
The conference concludes tomorrow.
