Professor Fowles and I explain at length in our paper the reasons for concluding that the 2016 Chicago homicide spike was caused by an “ACLU effect.” Specifically, we discuss an agreement that the Chicago Police Department struck in August 2015 with the ACLU regarding street stops (often referred to as “stop and frisks”). That agreement was implemented in December 2015, and produced about an 80% reduction in the street stops that Chicago police officers conducted during 2016. Our argument is simple: As a result of the ACLU agreement, police significantly reduced the number of street stops they made, leading to more illegal guns on the streets of Chicago, leading to more shootings and homicides. Our paper estimates that the reduction in street stops in Chicago led to about 245 additional victims killed and about 1,108 additional shootings during 2016.

The current pattern in Minneapolis may similarly reflect a reduction in police activity focused on preventing gun violence. As has been widely discussed in the media, the Minneapolis Council is moving to “defund” its police department–or, more precisely, to remake the police department into a “public safety department” with less focus on licensed police officers. Amid such discussions, officials in Minneapolis have noted (according to an article by the Star-Tribune) a “reluctance of some Minneapolis officers to take initiative amid intense scrutiny.”

This reluctance to “take initiative” could mean a reduction in street stops and other self-initiated police activity that might produce an increase in gun crimes.