Study: Chicago homicides spiked due to ACLU police decree

Paul Cassell is a law professor and former federal district court judge. Richard Fowles is an economics professor. Both teach at the University of Utah.

Cassell and Fowles have studied the spike of homicides in Chicago in 2016. Through multiple regression analysis and other tools, they conclude that an ACLU consent decree triggered a sharp reduction in stop and frisks by the Chicago Police Department, which in turn caused homicides to spike. In other words, what Chicago police officers call the “ACLU effect” is real. That effect was more homicides and shootings.

Cassell explains:

Our article proceeds in several steps. It begins by describing in general terms what is quite accurately called a “spike” in homicides in Chicago in 2016. A 58% year-to-year change [from 480 killed in 2015 to 754 killed the next year] in America’s “Second City” is staggering, suggesting something changed dramatically to initiate the increase.

We next attempt to pinpoint the time when things changed in Chicago—what might be called the “inflection” or “break” point in the data series. We begin by seasonally adjusting Chicago homicide and shooting data, which show significant seasonal fluctuation from cold weather months to warm weather months. Once the data are seasonally adjusted, a change or “break” in the data series can be statistically detected around November 2015.

We next explore the possibility that, as been suggested by a number of observers, a reduction in stop and frisks by the Chicago Police Department that began at the very end of 2015 was responsible for the homicide spike starting immediately thereafter. Good reasons exist for believing that the decline in stop and frisks caused the spike. Simple visual observation of the data suggests a cause-and-effect change. . . . November 2015 [is] the break point in the homicide data. This is precisely when stop and frisks declined in Chicago. . . .

Detailed regression analysis of the homicide (and related shooting) data strongly supports what visual observation suggests. Using monthly data from 2012 through 2016, we are able to control for such factors as temperature, homicides in other parts of Illinois, 9-1-1 calls (as a measure of police-citizen cooperation), and arrests for various types of crimes. Even controlling for these factors, our equations indicate that the steep decline in stop and frisks was strongly linked, at high levels of statistical significance, to the sharp increase in homicides (and other shooting crimes) in 2016.

Cassell and Fowles then searched for other possible factors that might be responsible for the Chicago homicide spike. None fit the data as well as the decline in stop and frisks.

Cassell and Fowles quantified the costs of the decline in stop and frisks in human and financial terms. They found that, because of fewer stop and frisks in 2016, a conservative estimate is that approximately 236 additional homicides and 1115 additional shootings occurred during that year. A reasonable estimate of the social costs associated with these additional homicides and shootings is about $1,500,000,000. And these costs are heavily concentrated in Chicago’s African-American and Hispanic communities.

What caused this deadly reduction in stop and frisks? In the final portion of their analysis, Cassell and Fowles show that it was the ACLU consent decree. This shouldn’t be controversial. The ACLU took credit for the reduction at the time.

Cassell and Fowles conclude by situating their findings within a larger body of developing empirical literature supporting the conclusion that restrictions on law enforcement investigations has real-world consequences by reducing police effectiveness. In Chicago, these consequences appear to be tragic, indeed.

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