Sentencing in New Zealand: a
statistical analysis
Foreword | Acknowledgements | Executive Summary |
Introduction | Chapter 2 | Chapter 3 | Chapter 4 | Chapter 5 | Chapter 6 | Chapter 7 | Chapter 8 | Chapter 9 | Chapter 10 | Chapter 11 | References | Appendix I | Appendix II | Tables | Figures
Executive Summary
Aim
The aim of this research was to quantify the relative effect of various statistical factors on current and past sentencing practice in New Zealand. A particular objective was to identify factors influencing the use of community-based sentences, including the extent to which community-based sentences are being used as an alternative to imprisonment and the extent of changes in sentencing practice that have accompanied the very significant increase in the use of community-based sentences over the last decade and a half.
Methods
A multivariate method (logistic regression modelling) was used to determine the independent effect of each statistical factor on the probability of receiving each sentence. Current sentencing practice was assessed using models based on all proved cases involving imprisonable offences finalised in 1995. These models were then used to predict the probability of each sentence for offenders sentenced in each of three other years (1983, 1987 and 1991). As these predicted probabilities take account of the differences in statistical characteristics of offenders in different years, a comparison of actual and predicted probabilities indicates the magnitude of changes in sentencing practice, independent of any statistical trends.
Only factors that could be quantified from the available statistical data were included in the analysis. These include the type and seriousness of the major offence committed, the number of charges proved in the current case, the plea, the previous criminal history of the offender (number and seriousness of previous proved cases, rate of conviction, the time since the last case, and previous sentences) and the sex, age and ethnicity of the offender. The total sample size was just under 300,000 cases.
While these are important variables in determining sentencing, this does not imply that other factors are not important, only that they could not be measured from the available data. Therefore, this analysis is not intended as a comment on sentencing with respect to specific cases (which always involve unique circumstances influencing the choice of sentence), but rather is intended as a broad overview of the combined effects of various statistical factors on overall sentencing practice at a national level.
Trends and relationships for the statistical variables
Multivariate methods consider the effects of all variables together, so that the independent contribution of each statistical variable can be estimated. This is necessary as many of the variables are interrelated. For example, the seriousness of the current offence is higher on average for cases involving several charges, for offenders with a more extensive previous criminal history, and for offenders who are male, of Māori or Pacific ethnicity, or aged under 17 years. Male, Māori and older offenders are also more likely, on average, to have an extensive history of previous offending.
Changes in the use of different sentence types may be due to changes in the type of offence or offender being dealt with by the criminal courts, rather than changes in sentencing practice. As the courts are now dealing with more serious cases than in the past, an increase in the use of more serious sentences would be expected. The key statistical trends between 1983 and 1995 are:
Changes in sentencing
Significant changes in the use of different sentences have occurred since the early 1980s. Some of these changes can be explained by changes in the type of offence and offender dealt with by the courts, as noted above. However, much of the change in sentencing patterns cannot be explained by these statistical trends. This suggests that changes in sentencing practice have occurred. That is, offenders with similar characteristics are now more or less likely to receive a specific sentence than they were in the 1980s.
The actual percentage of proved cases resulting in imprisonment has changed relatively little compared to changes in other sentence types. However, this lack of trend disguises a significant relative decrease in the use of imprisonment. Given the greater average seriousness of offences and offenders sentenced in 1995, the imprisonment rate should have been lower in 1983 than in 1995. Had 1995 sentencing practice been applied to the 1983 offenders, an estimated 6% would have received a prison sentence, compared the actual rate of imprisonment of 10% for 1983.
The relative use of imprisonment decreased particularly between 1983 and 1987, following the introduction of stricter guidelines on the use of imprisonment (Criminal Justice Act 1985) and between 1991 and 1995, following the introduction of the suspended prison sentence (Criminal Justice Amendment Act 1993). The relative use of imprisonment has decreased particularly for breaches of periodic detention, for offences of low to moderate seriousness, for offenders with several or many previous proved cases and for youth offenders.
The use of periodic detention has more than doubled in the last decade and a half. Trends in the type of offence and offender being sentenced explain around half of this increase, but there has also been a change in sentencing practice. The relative use of periodic detention has increased particularly for the offences and offenders for whom the use of imprisonment has decreased, suggesting that the decrease in imprisonment has been balanced by the increase in periodic detention.
The use of community service has more than trebled since 1983. Almost all of this change appears to be due to changes in sentencing practice. The very significant increase in the use of community service for offences of low seriousness and for offenders with very few previous cases indicates that community service is now being used where previously (in the 1980s) a monetary penalty would have been imposed.
The use of supervision increased between 1991 and 1995. This change centres on the increased use of supervision for domestic violence and other violent offences between 1991 and 1995. The use of supervision has also increased for offenders with several or many previous cases.
Monetary penalties are now much less often imposed for imprisonable offences than they were in the 1980s. About a fifth of the total decrease can be accounted for by changes in the type of offenders and offences dealt with by the court and the rest appears to be due to changes in sentencing practice. The imposition of community service, where previously a monetary penalty would have been imposed, accounts for much of this trend. The relative increase in the number of proved cases where a sentence is not imposed, or a community-based sentence other than community service is imposed, also accounts for some of the decrease in the use of monetary penalties.
Effects of each statistical variable
Effects of current case characteristics
The offence seriousness and the number of charges proved in the current case are among the most significant variables in the logistic regression models for prison sentences and monetary penalties. As the seriousness of the major offence increases or the number of charges increases, the probability of imprisonment increases and the probability of a monetary penalty decreases.
Community service is more often imposed for offences of relatively low seriousness (offences with a seriousness score between 1 and 60), while the use of periodic detention peaks for offences of low to moderate seriousness (a seriousness score of 20-180). Supervision and community programme show less of a relationship with offence seriousness, other than having a low probability for offences of very low or very high seriousness. The use of suspended prison sentences peaks for offences of moderate to high seriousness (a seriousness score of around 150-365).
The probability of receiving a prison sentence is greater if the most serious offence in the current case is an offence against the person (most of these being violent offences). This is particularly so for the serious types of violent offences, but is also true for the relatively less serious types such as assault and threats. This finding is consistent with the legal guidelines on the use of imprisonment for violent offences (Criminal Justice Act 1985).
Domestic violence is a key offence group for two other sentence types, supervision and community programme. Domestic violence is the most significant variable determining the probability of receiving these sentences. An offender is four to five times more likely to get supervision or community programme than another sentence if the current offence is domestic violence, compared to a statistically similar offender who has committed a property offence. Other offences against the person are also more likely to result in supervision or community programme.
If the current offence is a breach of periodic detention, then the odds of receiving a prison sentence or periodic detention are increased. Offenders who commit traffic offences have a higher probability of receiving community service, community programme, periodic detention or a monetary penalty, relative to property offenders.
A guilty plea appears to increase the probability of receiving community service, supervision or a monetary penalty, but decreases the probability of receiving a prison sentence or periodic detention.
Effects of gender, age and ethnicity
The results of the multivariate modelling indicate that females are more likely than males to receive community service, supervision, community programme or no sentence. On the other hand, females are less likely to receive a prison sentence, periodic detention or a monetary penalty. Gender is one of the most significant variables influencing the probability of receiving a monetary penalty or a community service sentence.
Offenders aged under 17 have an extremely low relative risk of receiving any of the sentences considered here, but especially the more serious sentences of imprisonment and periodic detention. This finding was expected, given the special legislative guidance and rules relating to the sentencing of youth offenders and the availability of sentences specifically for youth offenders. Offenders aged 17-19 or 30 plus are less likely to receive a monetary penalty, but more likely to receive community service, supervision, or community programme than offenders aged 20 to 29 years.
Māori and Pacific offenders are more likely to receive periodic detention, community programme or community service than Pakeha/Other offenders, but less likely to receive a monetary penalty. The use of imprisonment did not differ between ethnic groups, once other factors had been taken into account (such as the differences between ethnic groups in the seriousness of offences committed and in the extent of previous offending).
Effects of criminal history variables
Each of the criminal history variables shows some relationship to the probability of each type of sentence and various forms of these variables are significant in most of the models. The greater the number, seriousness and frequency of previous cases, and the shorter the time since the previous case, the greater the probability of a prison sentence and the lower the probability of a monetary penalty.
Criminal history is a distinguishing factor between offenders sentenced to periodic detention compared to community service. As the number of previous cases increases, the probability of periodic detention increases, whereas the probability of community service decreases. However, at very high levels of previous offending the probability of periodic detention decreases again, as imprisonment becomes more likely. The probability of a supervision or community programme sentence also tends to be higher for offenders with a moderate to high level of previous offending, but the criminal history variables are of limited significance in the models for these sentences.
Effects of previous sentences
The most recent sentence prior to the current case, and also other past sentences, have a significant influence on determining the current sentence. The previous sentence increases the risk of the same sentence or a more serious sentence, but decreases the risk of less serious sentences, all other factors being equal. For example, if the most recent sentence is a periodic detention sentence or the offender has had a periodic detention sentence in the past, there is an increased probability that the current sentence will be imprisonment, a suspended prison sentence or periodic detention, but a decreased probability of community service or a monetary penalty.
Interaction effects
'Fast-tracking' or sentence escalation
If having a previous community-based sentence decreases the probability of receiving a monetary penalty and increases the probability of receiving a further community-based sentence or prison sentence, then any increase in the use of community-based sentences may lead to a reinforcing cycle of sentence escalation, or 'fast-tracking' of offenders toward more serious sentences.
Therefore, the increased use of community service for offenders who would previously have received a monetary penalty may in turn have led to a greater use of community service and other community-based sentences for the same offenders when they are reconvicted. Following further reconvictions, the same process is repeated, increasing the use of more serious community-based sentences and ultimately putting pressure on the use of imprisonment.
With the increased use of community-based sentences a separate, but related, reinforcing effect is also likely. Increasing the number of people serving community-based sentences increases the number of people breaching these sentences. A breach of a community-based sentence, and especially a breach of periodic detention, puts the offender at higher risk of a periodic detention or prison sentence, thereby further reinforcing increases in the use of these sentences.
This cycle of escalation will only occur if offenders serving community-based sentences have a similar or higher rate of reconviction than offenders who receive a monetary penalty (i.e. if community-based sentences reduce the rate of reconviction then there would be fewer re-offenders to whom sentence escalation could apply). However, analysis of reconviction rates indicates that the sentence imposed is not a major factor in determining the probability of reconviction and that, if anything, offenders sentenced to a monetary penalty have a lower reconviction rate than those sentenced to a community-based sentence.
One effect of sentence escalation is increased pressure on the use of imprisonment, as offenders are 'fast-tracked' up the penalty scale to imprisonment sentences. However, the effect of this has been countered in practice by the change in the use of imprisonment relative to community-based sentences. In particular, the use of imprisonment has significantly decreased since the 1980s for offenders who have breached a periodic detention sentence, for offenders whose most recent sentence was periodic detention or community service, and for offenders with several previous convictions.
Alternatives to imprisonment and 'net-widening'
The original aims of extending the range of community-based sentences available and promoting the use of these sentences were to reduce the use of imprisonment and to encourage community involvement. Thus, community-based sentences were originally viewed as an alternative to imprisonment. Suspended prison sentences were also intended as an alternative to imprisonment.
Although imprisonment rates for many offences and offenders have decreased, these decreases have been very much smaller than the overall increases in the use of community-based sentences and suspended sentences. The widespread application of sentences intended as an alternative to imprisonment to offenders who would not otherwise have received a prison sentence is known as 'net-widening'.
One of the reasons it is so difficult to avoid net-widening is that there are a large number of offenders who have a moderate risk of imprisonment. As most offenders in this group receive a non-custodial sentence, it is possible to target the right general group of offenders, yet not actually impose the alternative sentence on the specific offenders who would otherwise have received a prison sentence. This is particularly so if, as for community service, the sentence is targeted at the lower end of the range, where the greatest numbers of offenders are.