Using the Offenders Index to investigate patterns of offending

The Offenders Index is a rich data source which consists of criminal conviction information collected from the courts. While it has been used to identify, for example, the proportions of particular birth years which have had a criminal conviction, there has been little interest in how the types of offences which offenders are convicted change over time. In this talk, we describe the problem of identifying patterns of offending behaviour, with the aim of identifying criminal lifestyles and how these might change over time. A latent class approach provides the methodological basis, and allows us to identify group profiles and the likely number of groups. While many offending patterns appear to be single offence, other offenders are involved in a mix of activity, some involving violence and others not. We observe strong changes over time and across birth cohorts, with the proportion of female offenders brought before the courts rising dramatically for some latent classes in later cohorts. While procedural changes offer some explanation of these results, social change will also play a part. 3 Introduction The aim of this paper is to provide a general overview of an ongoing research programme on criminal careers which seeks to use the Offenders Index to explore a variety of issues related to changing patterns over time. In our work there are both substantive issues-which involve investigating changes in the patterns of criminal careers over the life course and specifically focusing on the nature of offending-and methodological issues – which involve developing new methods for assessing changes in the nature of offending over time and to take advantage of modern administrative datasets such as the Offenders Index. After a brief summary of some of our work to date, this paper provides some initial thoughts and preliminary findings on disentangling age, period (or year) and cohort (or generational) effects when considering changes over time.