Are there distinct patterns of offending over time such that some individuals follow one course (e.g., peaking in adolescence and desisting as adulthood approaches) over another (e.g., peaking early in life, remaining active throughout life, and hardly desisting later in life)? Or is it the case that most offenders follow a similar path to offending such that it is unnecessary to postulate distinct patterns of offending and the theoretical and methodological complexity associated with them? Such questions strike at the heart of classic and contemporary criminological debates as well as policy discussions, options, and decisions.

One set of theorists claims that there are two different groups of offenders, each exhibiting a distinctive shape, peak, and pattern of offending over the life-course (e.g., Moffitt, 1993; Patterson, 1993). The first group is believed to be characterized by a very small number of individuals who evince an early onset of offending and a fairly flat trajectory of criminal activity throughout much of the life-course. These individuals offend early, offend more often while active, and are relatively unlikely to desist. A second group of offenders is believed to be characterized by a relatively large number of individuals who first engage in delinquent and criminal activity in their teenage years; however, at some point in their early adulthood these individuals curtail their offending activity and move on to more conventional adult patterns.