Update 3 December 2016: This post has been retracted. The conclusions contained in it are not supported by the data. A post explaining this is more detail is here.

Update 2 January 2017: After I retracted this post, the Ministry of Justice got in contact, apologised for failing to meet the high standards they set themselves, and offered to provide comparable data. A new post, with a fair comparison, is up here.

It now a bit over five years since New Zealand introduced the three strike sentencing regime for “serious violent crime”. And, after some news coverage about this a few months back, I decided I’d try to find out how well it’s working. It may surprise you to learn that the evidence to date suggests it is having a deterrent effect. More on that later. New Zealand’s three strikes law has always been a much more targeted law than its North American namesakes. It is designed to avoid particularly unjust outcomes, covering a relatively narrow range of offences, and it allows for *some* of its potential harsh consequences to mitigated in the event of a “manifest injustice”. This has seen for example, what would have been the first two sentences of life without parole (the consequence of a murder committed as a second strike or a third strike) avoided, as explained by Andrew Geddis here (avoided for now at least, as the Crown is appealing both decisions).

Even with these decisions, and the really rather low likelihood of it causing a massive injustice, I still oppose three strikes. Applying the proviso can only get you so far. The “manifest injustice” exception only applies to the non-parole period. It can, as it has, turn what may have been an unjust sentence of life without parole into a more just sentence of life with the possibility of parole. It cannot turn what may have to be a mandatory life sentence for a manslaughter into anything less than a life sentence. Now, I have to concede that the situations where something really unjust will happen are unlikely, but they remain possible, especially with the expansion of the scope of burglary, about which I’ve written before. Now, burglary isn’t a strike offence, but aggravated burglary is, which is any burglary committing while in possession of a weapon (the weapon doesn’t need to be used). And while high school lunch money stand overs are never prosecuted as aggravated robberies, or even as robberies, the idea that everyone convicted of a listed offence was committing something we’d agree was a serious crime is problematic. One of the good things about New Zealand’s three strikes system is that it is in no way retrospective. At least some of the three strikes regimes in the United States are retrospective in part. While none increase the penalties for offending committed before they were passed, the higher mandatory penalties they impose can be affected by convictions entered before the law was adopted.

In New Zealand, convictions that pre-date the law don’t count as strikes, and offending that pre-dates the law, but which was prosecuted after the law change doesn’t count either: not even for a first warning (which has no effect other than being needed before something can later count as a second strike). New Zealand’s three strike regime has an element of formality to it. Offending can only count as a second strike if the offender has actually been convicted of a strike offence before the new offending occurred. Conviction is formal step, distinct even from a finding of guilt, and when it occurs, the judge is required to read out (and provide a copy of) a formal warning of the effect of a subsequent. Judges are likely to also remind offenders of the warning at sentencing, which, for serious charges, is usually a separate event. I suspect that the principle rationale of supporters of three strikes in New Zealand was not deterrence, but incapacitation. They looked at the people committing really serious crimes like murder, saw that many have long criminal histories, and decided that if those people had been detained for longer for their earlier crimes, they wouldn’t have been in a position to commit the more serious crimes they later engaged. It has a certain logic to it, but, of course, it captures people with similar criminal histories who would not have later committed murder.

Supporters of three strikes point to the reduction in violent crime in California after the introduction of its three strikes regime (generally regarded as the strictest form) as evidence that it “works”. This argument is invariably followed by the counterpoint: crime was down a similar amount in New York, and New York didn’t have three strikes, so maybe crime was just down everywhere, and three strikes had nothing to do with it? This, naturally, is followed by the rejoinder: New York may have not have had three strikes, but they did adopt sentencing enhancements, which can have a similar effect on sentencing. It’s an oft-repeated argument: someone will point out that our imprisonment rate is increasing, even while our crime rate is decreasing. To which the response will be that the crime rate is decreasing precisely because the imprisonment rate is increasing. The argument is all but impossible to resolve. But, in New Zealand at least, we have a chance to test whether the three strikes law is working. And early indications are that it may well be. A couple of months back, Stuff carried an article looking at three strikes five years on. It was picked up on Kiwiblog – which played up the deterrent effect: “So 98.6% of offenders who got a first strike, have not gone on and committed a second strike offence. That’s great. The certainty of knowing that they will not get parole if given a second strike appears to be a strong deterrent.” And it was picked up on The Standard, which called the arguments “innumeracy”. I questioned David Garrett about his conclusions in the comments thread of the Kiwiblog post:

“Three strikes was intended to work in two ways: first and foremost, to protect the rest of us by incapacitation of repeat violent offenders, i.e by putting them in jail where they cannot harm the rest of us. Secondly – hopefully – by specific and general deterrence. I would be very interested if someone has a better theory as to why have 5400 first strikers five years on, but only 76 second strikers, when the vast bulk of the first strikers have served their first strike sentence, and are thus on the street. It is of course impossible to prove deterrence, as it is impossible to prove any negative.” 76 second strikes does seem low (turns out that it’s really 81, but that seems low too). But I’d be wildly speculating if I was to offer reasons why it might be low: has National instituted a wildly successful rehabilitation programme for serious offenders? I have no idea. I asked David (Garrett, not Farrar), whether he was sure the number was in fact low: “What are the comparison numbers for the five years before the three strikes law took effect? How many people were convicted of an offence listed as a strike offence during those five years, and how many were convicted of a second or subsequent strike offence committed after that conviction was entered?” He didn’t know. Neither, of course, did I. I decided to find out. It seems the obvious comparison in any assessment of the deterrent effect of three strikes. We know how many second strikes there have in the five years since it entered into force. How many would there have been in the five years prior to three strikes had the same rules applied? To the Official Information Act!

You need to be careful when crafting OIA questions around this sort of comparison, and I am relying on the Ministry of Justice to have correctly understood my intention. It is not enough to compare the number of convictions before and after the law change. Almost a third of convictions for “strike” offences since three strikes was enacted haven’t attracted first warnings because they relate to offending that occurred before the law change. You need to exclude similar offending in the comparison. Between 1 June 2005 and 31 May 2010, 6809 people received convictions for strike offences that occurred between 1 June 2005 and 31 May 2010. Between 1 June 2010 and 31 May 2015, 5422 people received convictions for strike offences that occurred between 1 June 2010 and 31 May 2015. So strike crime is down around 20% since three strikes came into effect. Claiming cause and effect over something like that is the type of intractable debate that you get into over the effect of longer prison sentences. But what we are looking at is not the general deterrent effect of three strikes (fear of punishment in the public at large), but specific deterrence: fear of punishment by those who have a conviction for strike offending who have been personally warned by a judge that further strike offending is treated very seriously. And that is where we can check the comparison between the five years before three strikes and the five years after it.

We know there were 81 second strikes in the first five years of three strikes. These are people who have been convicted for committing a strike offence after the law came into force, and subsequent to that conviction, been convicted of a further strike offence, itself committed after their earlier conviction occurred. The pre-strike comparison therefore needs to be people convicted of an offence committed after 1 June 2005 (but before 31 May 2010), who were then convicted before 31 May 2010 of a further offence committed after that conviction. And it turn out that that number is a lot higher. Had the three strikes law been in place on 1 June 2005, the following five years would have seen 256 offenders receive second strikes. Now, strike crime is down in general, but the ~20% fall in strike offending is dwarfed by the ~62% fall in strike recidivism. Now, I hear you argue, if the three strikes regime had been in place earlier, then people might have acted differently. Well, you’re probably not arguing that, because the usual approach of the type of people likely to reading an article on Public Address, has been what Denis Dutton once apparently described as the “feverish search for ‘the real reason’” for the decline in violence. I am, of course, open to alternative explanations: perhaps, in June 2010, the Government also introduced some highly successful treatment programmes, so that a person in prison for strike offending in 2011 has a much better chance of turning their life around than a person who was in prison five years earlier. I doubted such a treatment programme exists, but I decided to follow that up with a further OIA request.

Because of the lack of retrospectivity in our three strikes law, two people convicted on the same day, in respect of the same charge can have different strike consequences: someone convicted for offending that occurred after the law came into force receives a strike warning, but someone convicted of an offence committed before the law was enacted receives no warning. A comparison between these two groups may help confirm or quash the alternative hypothesis that some change in treatment is the cause of the substantial reduction in strike recidivism. In the first 4 years and 7 months of three strikes (curse you tier one statistics!), 2437 people have been convicted of strike offending that did not result in a strike warning, and of those, 360 had subsequently earned a first warning for an offence committed after that conviction. That’s a strike recidivism rate over 1000% higher among those who didn’t receive a warning than those who did. Of course, this direct comparison is misleading, as the post-strike convictions for pre-strike offending will be front-loaded, occurring on average much earlier in the ~5 year period since three strikes was enacted, and thus allowing more time for strike-level recidivism to occur. However, it remains useful, as it provides evidence to negate the alternative explanation for the pre-strike/post-strike comparison of much improved recidivism treatment. And that is what we are left with: in the first five years of three strikes, there were 81 second strike convictions. In the five year before three strikes, there would have been 256. 81 second strikes seemed low. Now we know it is.

And given that strike-level recidivism has dropped much faster than strike-level offending, it’s useful to ask why. I am particularly sceptical of general deterrence, am more accepting of the idea that incapacitation decreases crime (though am concerned about the cost), and am intrigued by the idea that personal deterrence, through the formal three strike warning, may actually work. I got to this point by saying “81 second strikes sounds low, but is it?” Confirming it is leaves more questions. But the possibility that the three strike law is having a deterrent effect still leave unanswered questions. Of course, there may be other explanations, and if so, I would welcome falsifiable hypotheses. If people would like to offer some alternatives, it may be possible to graft OIA requests that may rule some of them out. More help may come if we can make the analysis in the second (currently flawed) comparison, more granular: breaking the results down by year, or even month should enable a comparison which isn’t as affected by front-loading. I guess my question is: if you are sceptical of the deterrent effect for second and third strike consequences, what evidence would it take for you to convince you? Establishing clear cause and effect will be impossible, but providing enough evidence to reach a conclusion that three strikes is probably (or probably not) having a deterrent effect should be possible. We have some data already – strike recidivism appears to be falling much faster than strike offending, so what more do we need?