Criminals like Al Capone, Bonnie and Clyde and John Dillinger were headliners of the era.

Jobs were scarce and people needed to provide for their families, gangsterism was dangerous but provided an easy way to make money. When the American government passed the Eighteenth amendments outlawing alcohol, people who enjoyed a drink became criminal for doing so.

It was organized crime who supplied the booze. In January of 1920 the American government banned the sale and supply of alcohol, the government thought that this would curb crime and violence, prohibition did not achieve it’s goals, leading more toward higher crime rates and excessive violence.

Alcohol was seen as the devils advocate and banning the substance would help improve the quality of American lives. It caused an explosive growth in crime with more than double the amount of illegal bars and saloons operating than before prohibition.

The American government set up the "Federal Prohibition Bureau" to police prohibition, this did not deter people and organized crime continued to be the main supplier of booze.

Bribing government officials was common, and people were increasingly crafty in the way they would hide  alcohol such as hollowed out canes, false books and hip flasks. Violence on the streets increased as did unemployment. Ironically, had prohibition never happened organized crime syndicates may not have become so wealthy or powerful.*

What a time the 1920’s was, with the party atmosphere it was certainly a time of great criminal activity, with the prohibition laws in America and the world in an economic depression.

The people turned more and more to criminal activity, organized criminals such as the American mobsters and European crime syndicates thrived, most common people looked upon these organizations as heroes.

In the UK, things were becoming more intense as well. In the 1920s and 1930s the London and national press reported extensively on what appeared to be outbreaks of gang crime bearing a similarity to the forms of organised crime that had recently been reported in Italy and North America.
At the start of the 1920s, home-grown gang violence had been mainly confined to the racecourses and cast largely as an unwelcome development of traditional forms of racecourse criminality. By the middle of the decade the incursions of the racing men onto the London streets provoked intense report-age. In London, violent street conflicts were characterised by press, police and politicians as a form of terrorism. The Evening Standard, for instance, described a tense search for ‘racecourse terrorists’ in the West End **:

‘While Scotland Yard is thus rigorously engaged in hunting down the terrorists,
the “enemy” is employing a sort of secret service to ascertain the movements of detectives.’

Is YOUR character involved in this level of crime, or are you a petty thief or con-artist? Why is your character a criminal? Hard-times and hard-luck is all well and good, but don't be a walking stereotype or you may end up quickly "sleeping with the fishes"...

* Taken from: http://www.thefinertimes.com/20th-Century-Crime/organised-crime-in-the-1920s.html

** London’s Criminal Underworlds, c. 1720–c. 1930