Analysis - If Andrew Little had forgotten how hard it will be to liberalise the criminal justice system, two colleagues reminded him on the very night he began his task.

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The Criminal Justice Summit, which is to lay the foundations for an advisory group to then flesh out the government's goal of reducing the prison population by 30 percent, opened in Porirua on Monday.

About 20km south of there Police Minister Stuart Nash and Deputy Prime Minister Winston Peters were at Parliament announcing 1800 more police.

The government is claiming the new police will help prevent crime happening in the first place.

Maybe. But it's not hard to see it in other terms: that this is the type of 'tough on crime' approach that has led to our prisons bursting at the seams.

What do we really expect to result from 1800 more police? Presumably many of them will be trying to catch more people breaking the law, leading to more people being locked up.

If you think that is too simplistic look at the 2017 Briefing for the Incoming Minister of Corrections, in which the department warned the prison population was going to blow out to 12,000 by 2026.

It laid out the drivers of that increase and one of them was "additional police numbers" leading to "more arrests and prosecutions".

Now this might not happen if a new approach is taken to offenders rather than putting them in jail.

But this doesn't seem to be what Justice Minister Andrew Little has in mind. "Of course people will continue to go to prison," Little told TVNZ's Q + A the night before the summit opened, adding that "prison is a response to a lot of offending."

It seems that for him this exercise is about what we do with prisoners when they are in there: the quality and extent of rehabilitation. "If we can reduce the reoffending rate we can reduce the prison population."

Now it'd be hard to find someone who doesn't think it's a good idea to put a lot of energy and resources into rehabilitation.

But is this really going to lead to a 30 percent drop in prison numbers? And isn't waiting until someone is in prison and hoping to turn their life around at that point, tackling the problem from the wrong end?

We've long known how critical the first few years of life are. If 'evidenced based policy' is what you're looking for you'll find plenty about the benefits of concentrating on the quality of life for young children in families with high challenges.

And yes the government is trying to address this. Its Best Start package gives a family $60 a week for their child's first year - and for two subsequent years if they earn under $80,000. But these are small gains that could take a long time to bear fruit.

What I am yet to hear - and I hope I do - is a coherent strategy to reduce the prison population by anything close to the 30 percent Labour aims for over 15 years.

That will require radical change and it is hard to get political buy-in for radical change in the justice sector. National is going to cut Little no slack and will seize on chances to label him 'soft on crime'.

Little faces challenge from within as well. Already New Zealand First has killed off his promise to ditch the Three Strikes law. Will it give its crucial votes to support radical liberal reform of the justice sector?

Peters comments when announcing the 1800 new police didn't sound encouraging on that front.

He cast some of the new officers as combatants in the front line of the drug war, saying they will make "a huge difference to combat the methamphetamine scourge and improve safety in our communities".

Are more police the answer to our problems with drugs? Can we rehabilitate enough serious offenders to make a serious dent in the prison population? And perhaps most vexing of all, can we turn around the depressingly intractable fact that half the people locked up are Māori?

There were 700 policy experts at the Justice Summit. Now a 10 member advisory group will thrash the issues out. But ultimately there's only one Justice Minister and one mighty challenge for Andrew Little.

*Guyon Espiner is co-host of Morning Report on RNZ. He covered politics from the Press Gallery between 1998 and 2011 and produced the 9th Floor book and podcast series with RNZ's Tim Watkin.