Common sense combined with education (biology, chemistry, psychology…) and observation (statistics, history…) points to three root causes of crime. Crime is usually if not always a function of one or more of money, hormones, and mental defect.
Money is an easy one. The vast majority of crimes are due to money. Robberies, theft, muggings, embezzlement, extortion, kidnapping, the list goes on. Nobody is immune to it either. The poor are susceptible to money-crimes because they need it and don’t have it (desperation). The rich are prone to money-crimes because they have a taste of it and want more (greed). It is not generally treatable other than with money. Unfortunately, society is not likely to vanquish hunger, homelessness, and such anytime soon since it is just too pervasive, so until Star Trek replicators are invented, this will continue to be the most common cause of crime. “Money is the root of all evil” indeed.
Hormones are pretty easy too, they are the second leading cause of crimes. Rape, adultery, pedophilia, assault, battery, manslaughter. Again nobody is immune to hormone-crimes since we all have them and frankly there is no defense against them; they affect our brains directly. Usually they are caused when a person has too much of a hormone, although a deficiency can also cause it. There are two kinds of hormone-crime, sex and violence which can even be combined. Hormones are the best candidate for treatment. They are not something that is overwhelmingly widespread like money, nor is it a permanent condition like mental defect. When properly diagnosed in time, the right medications or therapy can help treat or even cure hormonal imbalances and thus prevent hormone related crimes.
Mental defect is rarer than the other two. Mental defect-crimes are popular material for books and movies because they allow for unusual characters and an edgy and uncomfortable scenario. Crimes committed by people with mental defects don’t really have a tangible motivation; they commit them because the act itself gives them satisfaction—the act is the goal not the tool to achieve something else. Serial killers, people who delight in the torture and maiming of people and animals, pyromaniacs, kleptomaniacs, and the like all have some sort of defect in their brains that causes them to behave in an abnormal and destructive way. Mental defects are not usually curable. Like height, gender, skin color, etc. they are just part of who the person is since the brain cannot currently be “re-wired”. Unfortunately those who are “criminally insane” are more or less condemned to being put away in a state hospital for life. “Crimes of passion”, those done for love can be caused by either mental defect or possibly just a hormonal imbalance (ie, temporary insanity). A less movie-worthy cause of crime due to mental defect is when a person simply does not understand what they are doing is wrong because they either do not have the mental capacity in general (a “mentally-handicapped” person) or they have a defect that prevents them from understanding why it is bad (eg a sociopath who cannot relate to their victims).