For the not-yet-homeless, there are two main paths to criminalization  one involving debt, and the other skin color. Anyone of any color or pre-recession financial status can fall into debt, and although we pride ourselves on the abolition of debtors’ prison, in at least one state, Texas, people who can’t afford to pay their traffic fines may be made to “sit out their tickets” in jail.

Often the path to legal trouble begins when one of your creditors has a court issue a summons for you, which you fail to honor for one reason or another. (Maybe your address has changed or you never received it.) Now you’re in contempt of court. Or suppose you miss a payment and, before you realize it, your car insurance lapses; then you’re stopped for something like a broken headlight. Depending on the state, you may have your car impounded or face a steep fine  again, exposing you to a possible summons. “There’s just no end to it once the cycle starts,” said Robert Solomon of Yale Law School. “It just keeps accelerating.”

By far the most reliable way to be criminalized by poverty is to have the wrong-color skin. Indignation runs high when a celebrity professor encounters racial profiling, but for decades whole communities have been effectively “profiled” for the suspicious combination of being both dark-skinned and poor, thanks to the “broken windows” or “zero tolerance” theory of policing popularized by Rudy Giuliani, when he was mayor of New York City, and his police chief William Bratton.

Flick a cigarette in a heavily patrolled community of color and you’re littering; wear the wrong color T-shirt and you’re displaying gang allegiance. Just strolling around in a dodgy neighborhood can mark you as a potential suspect, according to “Let’s Get Free: A Hip-Hop Theory of Justice,” an eye-opening new book by Paul Butler, a former federal prosecutor in Washington. If you seem at all evasive, which I suppose is like looking “overly anxious” in an airport, Mr. Butler writes, the police “can force you to stop just to investigate why you don’t want to talk to them.” And don’t get grumpy about it or you could be “resisting arrest.”

There’s no minimum age for being sucked into what the Children’s Defense Fund calls “the cradle-to-prison pipeline.” In New York City, a teenager caught in public housing without an ID  say, while visiting a friend or relative  can be charged with criminal trespassing and wind up in juvenile detention, Mishi Faruqee, the director of youth justice programs for the Children’s Defense Fund of New York, told me. In just the past few months, a growing number of cities have taken to ticketing and sometimes handcuffing teenagers found on the streets during school hours.

In Los Angeles, the fine for truancy is $250; in Dallas, it can be as much as $500  crushing amounts for people living near the poverty level. According to the Los Angeles Bus Riders Union, an advocacy group, 12,000 students were ticketed for truancy in 2008.

Image Credit... Heads of State

Why does the Bus Riders Union care? Because it estimates that 80 percent of the “truants,” especially those who are black or Latino, are merely late for school, thanks to the way that over-filled buses whiz by them without stopping. I met people in Los Angeles who told me they keep their children home if there’s the slightest chance of their being late. It’s an ingenious anti-truancy policy that discourages parents from sending their youngsters to school.