Early criminologists believed that crime was a choice based on an individual's free will, but the field expanded to include biological, psychological and sociological explanations of crime. Poverty, family structure, and capitalism are among some of the widely debated root causes of crime. Criminologists consider what motivates offenders as well as the impact of crime on victims and society as a whole. By studying the causes of crime, criminologists can offer practical solutions to reduce or even prevent certain types of crime. Criminologists have been instrumental in evaluating criminal justice policies such as Megan's Laws, mandatory sentencing for drug offenders and Three Strikes laws.