The non-consequentialist approach to punishment sentences on the basis of offence-seriousness. However, there has been little theoretical or empirical consideration of the notion of offence-seriousness. Identification of ‘serious’ offences tends to be commonsensical at best. Further, there is currently no systematic way of measuring changes of seriousness over time. This study is a demonstration project displaying a way to investigate how the judiciary and the magistracy rank offence-seriousness in assessing actual cases. The use of paired-comparisons methodology provides a procedure which overcomes some problems of previous approaches. The method enables an assessment of the performance of judges and magistrates in terms of how they view the seriousness of offences without the artificiality of being involved in hypothesized field experiments.