So, they don’t ask, for instance: Is there one group of officers who are getting us into trouble?

In Chicago, law professor Craig Futterman found the answer to that was "yes."

Futterman, who runs the University of Chicago's Civil Rights and Police Accountability Project, has won some cases against police. For one such case, he got the numbers on whether some officers had an unusually-high number of complaints against them.

As it turned out, a relative handful accounted for almost half of all complaints, and they were almost never disciplined.

"There’s a small percent who have been allowed to just do this with darn near impunity," he says. "Despite the bills racking up, and despite all the complaints."

He also found that the Chicago Police Department had never run the numbers to identify those officers.

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