Street crime is caused by a combination of individual and external factors. Some external factors include social circumstances, such as poverty, degraded urban environments, lack of social support and gang activity. Some individual factors include negative emotions, such as anger, fear or mistrust and relationships with criminals.
Street crime is such a complex issue that an entire academic field developed to study it: the science of criminology. Criminologists attempt to study the root causes of crime and determine ways that future crimes can be prevented.
The science of criminology evolved as a sub-branch of sociology. Its first champions were 18th-century writers who felt that the justice system was arbitrary, cruel and inhumane. One such prominent writer was the Italian theorist Cesare Bonsano Beccare, who argued that the justice system must apply the law equally to all individuals. The English theorist Jeremy Bentham agreed with Beccare and added that punishments should be devised to deter individuals from committing crimes, rather than as sadistic torture dreamed up after the crime has been committed.
Both theorists held that individuals are motivated by the pursuit of pleasure and the avoidance of pain; therefore, they propagated the idea that punishments should be made severe enough that the fear of them outweighs the possibility of gaining pleasure from committing a crime.