Drug addiction is also said to lead to harder crimes, but that's actually more an issue of poverty.
[WS:] Actually, it is the issue of the dynamics of drug trade, dealers, enforcers and the legal system that enables their trade, rather than poverty. The dealers and enforcers literally force addicts to criminal acts by high prices and threats or acts of violence. If drugs were legal, the price would go down, availability would increase, and the dealers and enforcers would go out of business - perhaps becoming regular criminals themselves.
More generally, I fundamentally disagree with the proposition that poor people are more likely to break the law than rich people, as it is commonly believed, even on the left. I think the opposite is true. Everything else being equal, it is the rich people and their sense of entitlement that makes them more likely to break the law. However, they are better at concealing their criminal activity, seldom get caught, and if they do they not called criminals.
I think that poor people generally have a higher sense of responsibility, reciprocity, obligation toward others and adherence to social/community norms than the rich people. From that standpoint, they are less likely to break the law and prey on others than the rich people.
What makes it more likely to be a criminal is, for the most part, enabling social environment and peer pressure not individual desperation and decisions to "get ahead" or "get even." The poor people are more likely to be exposed to criminal subcultures and networks that condone and encourage criminal behavior, preying on others, and violence as the means of getting ahead. Therefore, poor people are more likely to be drawn into criminal activity by these subcultures and networks.
Of course criminal subcultures and networks also exist among the rich - in corporations, law firms, government, lobbying firms, country clubs, social circles - however, their net influence on the rich is far lesser for a number of reasons. First, the rich as a group generally experience less neglect and abuse as children, and thus are far less likely to be desperate to "belong" - which is one of the main drawing force into criminal networks for the poor. Second, the rich have a wider variety of functioning networks available to them in addition to criminal ones, whereas for many poor a criminal gang is probably the only semblance of organized community available to them. Third, the rich stand more to lose if they are caught in a criminal act, while the poor lose very little and sometimes even gain a bit (e.g. shelter and food, even if it is a jail).
As a result, the rich/middle classes are less likely - as a group - to engage in criminal activity than the poor, even though they are more likely to exhibit the attitude of individualistic entitlements which makes them more prone than the poor to break the law for personal benefit.
Wojtek