ABSTRACT
There are three foundation stones for understanding criminal careers. Onset is the first and persistence and desistance are to follow. This chapter focuses on the key issue of onset, which refers to the beginning of a criminal career. While this sounds simple enough, defining the concept of onset is not always straightforward and there is, in fact, no universal consensus among researchers on exactly how we measure the ‘start’ of criminal behaviour. Some studies focus on official criminal records to identify age at first arrest or age at first conviction as the defining ‘moment’ of onset. Others use self-report data to consider the age when individuals first report breaking the law or ‘getting into trouble’. To add further confusion, it can be difficult to make international comparisons in this area (at least between studies based on ‘official’ data), as the age of criminal responsibility (and therefore the age at which one can be officially convicted of a crime) varies widely across the globe.
