Before talking about what forensic and criminal psychology is, we must define criminal behaviour first. Criminal behaviour suggests a large number and variety of acts. It is difficult to define criminal behaviour as ideas of what is considered immoral, unconventional, illegal forensic psychology and sex offenders antisocial is not stable over time or place. Delinquency must be distinguished from criminality.
Delinquency is defined as behaviour that is illegal, immoral or deviant with respect to societal values. Criminality on the other hand is defined as a breaking of existing laws, there is little or no confusion as to what constitutes illegal and legal behaviors. When measuring criminal behaviour we are trying in a way to predict future criminal behaviours. We may measure criminal behaviour by arrests and charges, however not everyone charged is found guilty.
We can also measure the amounts of convictions and incarcerations. We can also measure the amount of self-reported offences and some believe that this may be a more accurate way to measure criminal behaviour. Estimates of actual crime rates are usually obtained from official sources, yet different sources may yield different estimates. Crime reports generally categorize crimes by type of crime and offender characteristics such as age, gender, race and location. By estimating crime rates we want to predict recidivism. Recidivism is the future criminal offences following a previous offence and is defined through new arrests, new charges and new convictions. In general the best single predictor of recidivism is number and type of previous criminal offences, and these rates will vary due to age, gender and type of crime.