Furious at the verdict, the state police union issued a veiled threat the same day asking whether citizens of Chicago were “ready to pay the price” of police officers not feeling comfortable doing their jobs. And while the Chicago Police Department has denied there was any work slowdown, an analysis of crime data by VICE News shows a significant reduction in police activity following Van Dyke’s sentencing on January 18.

CHICAGO — Soon after Chicago police officer Jason Van Dyke was sentenced to almost seven years in prison for gunning down 17-year-old Laquan McDonald, his colleagues did something fairly common to frustrated police departments: They started working less.

Chicago Mayor Lori Lightfoot even used a press conference with the city’s police chief to note the improvement, saying the city was “trending in the right direction but has a long way to go.”

In the weeks and months following Van Dyke’s sentencing, serious crime continued to decline even though cops had returned to more active policing. So far in 2019, the number of homicides — which was previously among the highest in the U.S. — has dropped by 8%. Murders have fallen to their lowest level in five years. Shootings are down 9% compared to last year. Police were doing less, but somehow Chicago became safer.

Police see slowdowns as a way of punishing a community by letting crime flourish unaddressed. But in Chicago, something unexpected happened: While arrests and crime reports by police fell during the two-week slowdown, they stayed low when police returned to work.

Arrests by Chicago police officers dropped by nearly 50% citywide the evening after the sentence came down, and almost 25% in the two weeks following. At the same time, total crime as reported by police dropped to the lowest level in at least two decades, a stat consistent with a policing slowdown. Crime reports arising through street stops, such as drug arrests and weapons violations, fell the most precipitously, as officers continued to respond to serious incidents like shootings.

The proof of a slowdown lies in the fact that three particular kinds of arrests virtually stopped: drug possession, weapons violations and prostitution. This is important because narcotics, weapons and prostitution arrests are an indicator of a type of policing known as “proactive,” in which officers initiate encounters with citizens without the report of a crime. This can include stopping people based on “suspicious activity” — which can be interpreted as standing on a particular corner or moving away from a police car. Proactive policing is a fraught and controversial practice, as people of color are often disproportionately targeted.

Between January 18 and January 31, the two weeks after Van Dyke’s sentencing, police made less than one-third the average number of narcotics arrests in the previous 18 years. Prostitution arrests fell by about 90% from the average over the same time period. Weapons violations dropped as well. The massive decline suggests that officers weren’t stopping people on the street nearly as often.

“It’s possible that [citizens said], ‘OK, finally somebody’s doing something; they’re listening.’”

During the slowdown, the crime reduction was also concentrated within black and Latino communities on the city’s south and west sides with higher crime rates, suggesting that different groups of police officers responded to the union calls for a slowdown differently. Former Baltimore police officer and professor of law and police science at the John Jay College of Criminal Justice Peter Moskos said many cops ignore such statements by the union.