Attorney General Jeff Sessions blamed the American Civil Liberties Union for the uptick in 2016 Chicago homicides in two speeches, one on May 8th addressing the Gatlinburg Law Enforcement Training Conference and one Monday night to the National Association of Police Organizations.
Sessions based his claim on a paper by University of Utah professors Paul Cassell and Richard Fowles. (It's worth noting that Cassell is a former federal judge and defender of law-and-order policy.)
The professors claim that murders spiked in Chicago because of an agreement between Chicago and the ACLU that requires police to document each street stop, or "stop-and-frisk," that they conduct.
In their paper, Cassell and Fowles found that the number of stops decreased by 75 percent in 2016, the year following the agreement. Homicides also increased by 60 percent in 2016. The professors call this outcome the "ACLU effect."
Unfortunately for Sessions, the paper he drew conclusions from was both limited and flawed.
Other Crimes in Chicago Did Not Experience a Similar Uptick in 2016
Stop-and-frisk policies should, in theory, affect all crimes, not just homicide. But Chicago did not see as dramatic a jump in crimes besides homicide in 2016. In fact, other research suggests that, when proactive policing slows down, there is often a greater increase in property crime than violent crime.
Large Cities With High Homicide Rates That Have Instituted Similar Policies Have Seen a Decrease in Crime
New York City's 2014 requirements corresponded with a steady murder rate and a decrease in crime. Philadelphia's similar settlement on stop-and-frisk in 2011 corresponded with a decrease in its homicide rate. Seattle's consent decree has included stop-and-frisk provisions since 2012, and the city's yearly homicide rate has remained mostly steady in the years since.
As a Statistics Teacher Might Say, Correlation Is Not the Same as Causation
The ACLU's response to Cassell and Fowles' conclusions points out that the professors' analysis only focuses on the drop in pedestrian stops. It does not test whether unidentified factors caused the police to perform fewer stops or caused Chicagoans to commit more murders. The report also failed to take into account vehicle stops: While pedestrian stops decreased, traffic stops doubled from 2015 to 2016.