Don't kid yourself -- now that cities and towns are so strapped for cash, this is going on in a lot of places. I know here in Philadelphia, there are people who linger in jail for months because they can't pay a small fine -- and then they're charged for each day they spent in jail. (Did you know we charge people for jail now?) These are, indeed, poverty crimes:

To understand some of the distrust of police that has fueled protests in Ferguson, Mo., consider this: In 2013, the municipal court in Ferguson — a city of 21,135 people — issued 32,975 arrest warrants for nonviolent offenses, mostly driving violations.

A new report released the week after 18-year old Michael Brown was shot and killed in Ferguson helps explain why. ArchCity Defenders, a St. Louis-area public defender group, says in its report that more than half the courts in St. Louis County engage in the "illegal and harmful practices" of charging high court fines and fees on nonviolent offenses like traffic violations — and then arresting people when they don't pay. The report singles out courts in three communities, including Ferguson.

Thomas Harvey, who started the organization to provide legal services to the poor in the St. Louis region and is the lead author of the report, says residents, especially in Ferguson, have come to see the use of fines and fees as a way for courts to collect money from residents who are often the least able to pay.

"Folks have the impression that this is a form of low-level harassment that isn't about public safety. It's about money," he says.

The ArchCity Defenders report argues that this resentment is justified. Last year, Ferguson collected $2.6 million in court fines and fees. It was the city's second-biggest source of income of the $20 million it collected in revenues.

Earlier this year, in the series Guilty and Charged, NPR's investigations unit found that the practices in Ferguson are common across the country. The series reported that nationwide, the costs of the justice system are billed increasingly to defendants and offenders, and that this creates harsher treatment of the poor. Because people with money can pay their hundreds or thousands of dollars in fines and fees right away, they are usually done with the court system.

People who can't pay their fines and fees go on payment plans. But then there are extra fees, sometimes interest — 12 percent on felonies in Washington state — and, if poor people fall behind on payments, they may go to jail. Courts often ignore laws, Supreme Court rulings and protections that outlaw the equivalent of debtors prisons.

Just like around the U.S., these municipal court fines in Ferguson are for low-level offenses, usually traffic violations. Harvey calls these "poverty crimes." Typically, he says, someone gets stopped for a rolling stop at a stop sign, or for a broken tail light. Then police find other problems.

"It's driving while suspended, no proof of insurance and failure to register a vehicle," he says.

The fines and fees can add up to hundreds, even thousands of dollars.

Data from the Missouri state attorney general's office show that black drivers are stopped in Ferguson in disproportionate numbers, even though Ferguson police are more likely to find contraband when they stop white drivers.

Blacks make up 67 percent of the city's population, but are 86 percent of motorists stopped by police. Whites make up 29 percent of the population, but 12.7 percent of vehicle stops.

"However, this data seems at odds with the fact that searches of black individuals result in discovery of contraband only 21.7 percent of the time, while similar searches of whites produce contraband 34 percent of the time," the ArchCity Defenders report notes.

In Ferguson, Harvey says going to court creates more anger. The system, he says, favors people who can hire a lawyer. But poorer defendants simply take a guilty plea.

"And then if you can't pay all the fines at once, they put you on a pay docket, and that just means [you] come to the court once a month and pay a certain dollar amount or explain why you haven't paid," Harvey says.