The police’s use of force showed similar disparities — with nearly 9 of 10 cases involving African-Americans. In every canine bite incident for which racial information was available, the person bitten was black.

The court system displayed the same biases. According to the report: “African-Americans are 68 percent less likely than others to have their cases dismissed by the court, and are more likely to have their cases last longer and result in more required court encounters. African-Americans are at least 50 percent more likely to have their cases lead to an arrest warrant, and accounted for 92 percent of cases in which an arrest warrant was issued by the Ferguson Municipal Court in 2013. Available data show that, of those actually arrested by F.P.D. only because of an outstanding municipal warrant, 96 percent are African-American.”

The arrests and fines of blacks were driven to some extent by the fact that Ferguson’s budget relies partly on fines and fees; city officials routinely urged the Police Department to generate more revenue through ticket writing. In 2013, for instance, the city finance director wrote: “Court fees are anticipated to rise about 7.5 percent. I did ask the chief if he thought the P.D. could deliver 10 percent increase. He indicated they could try.”

But budget needs could not explain, let alone justify, the pattern of racism. They merely combined with deep-seated biases throughout Ferguson’s power structure to entrap the city’s black community in a hellish cycle of arrests for minor offenses, fines they could not pay, to crippling financial penalties, loss of drivers licenses, and jail time. All of that meant lost jobs and eviction.

Not surprisingly, Ferguson’s African-Americans do not see the police as neutral enforcers of the law but as agents of exploitation. No municipality can prosper with that kind of hostility, overt or just below the surface, day in and day out. City officials should grasp this opportunity to take corrective steps. If they don’t, the Justice Department would be wholly justified in taking them to court.