The precise reasons for the drop-offs are unclear due to a lack of data.
This information deficit means, for example, that the commission could not say with confidence whether or not judges were following key sentencing principals set down in case law.
But the commission’s report speculated the trend could be due to a series of judicial reviews and constitutional challenges taken after legislation regarding judicial powers to suspend sentences was introduced in 2006.
It also said a number of practical and procedural difficulties with the law, which make it cumbersome in practice, may have played a part in “judicial reticence” to enforce the legislation.
In its report, the commission, which advises the Government on law reform, advocates the continued use of suspended prison terms in appropriate cases.
It also calls for further research to understand what was behind the decline and for key sentencing principals to be included in any guidelines drawn up for judges by the Judicial Council’s sentencing committee.
The report said suspended sentences should continue to be treated as compatible with the sentencing aims of retribution, deterrence and rehabilitation.
It said factors such as an absence of prior convictions, a guilty plea, remorse, co-operation with authorities, good character, age, illness, prospects of employment or education, prospects of rehabilitation, and family circumstances were particularly relevant mitigating factors for judges to take into account when considering the suspension of a sentence.
The report recommended that the use of suspended terms should be confined to adults and should not be expanded to child offenders.
It said detention of children was predominantly a welfare issue – while imprisonment of adults was primarily a punishment.
The report advised against the introduction of a separate sentencing regime for white-collar crime – an area where there has long been a perception of lenient sentencing – but did say the area would also benefit from sentencing guidelines.
The commission said a balance needed to be struck between white-collar offenders receiving due credit for mitigation and ensuring the gravity of the offence was marked by an appropriate sentence.
In particular, this should involve an assessment of the societal and individual harm caused by the offending.