Chicago police data reveals how dirty cops spread corruption like a disease

In 2009, after a successful public records lawsuit, the Invisible Institute received data on complaints against Chicago Police Department officers since 1988 — the complaints often list multiple officers, and by tracing the social graph of dirty cops over time, The Intercept's Rob Arthur was able to show how corruption spread like a contagion, from senior officers to junior ones, teaching bad practices ranging from brutality to falsifying evidence to torture to racism to plotting to murder whistleblowing cops.

The researchers were able to rule out some other explanations, like a likelihood that dirty cops will get the same kinds of assignments, tracing the relative levels of civil lawsuit payouts that different cops generated.

Criminologists and others who study police departments have long documented the "open secret" within police departments that some officers don't follow the rules, and also that other cops form a "blue wall of silence" to protect these lawbreaking officers. This data sheds light on the cost of that official tolerance of corruption, showing that dirty cops beget more dirty cops.

It's a kind of "broken windows" theory, but for bad cops. Let one bad cop hang around the force, and other cops will be tempted to break the rules, too. That's a real indictment of police unions, with their notorious habit of sheltering bad cops from official reprimands or job losses. This protection of crooked cops is rotting police forces from the inside.

Their behavior often escalates beyond complaints to more serious violence. The same cops who are exposed to other high complaint officers go on to be listed on four times as many uses of force per year in the next few years. They also commit shootings at rates more than five times higher than their colleagues who weren't exposed to misbehaving officers.

Stoughton credited part of the infectious quality of misbehaving officers to the process of training young cops. While officers learn the rules of policing at the academy, the probationary period provides hands-on training in the first few months on the job. In that time, many of the procedures they were told to follow in the academy get discarded. "On their first day, every cop hears some variation of 'Forget everything you learned at the academy'," Stoughton said.

Bob Verry, a retired police chief and current internal affairs investigator in New Jersey, likened the process of learning misconduct to the "broken windows" theory of policing, in which small violations escalate to larger and larger crimes. "Officers start out with minor things — forgetting their tie clip — and then that becomes forgetting to shine their shoes. … They get away with one punch during an arrest and it just goes on from there," Verry said.

Bad Chicago Cops Spread Their Misconduct Like a Disease [Rob Arthur/The Intercept]