HYDE PARK — Researchers at the University of Chicago’s Crime Lab said Tuesday they’ve crunched all the numbers and have been unable to find a clear cause for the dramatic spike in homicides in the city last year.
On Tuesday, the research group released its yearly report on gun violence in the city, citing possible causes, but failing to finger the exact reasons the city saw the largest year-over-year increase in homicides of any of the nation’s five largest cities in 25 years.
Jens Ludwig, the director of the crime lab, said there are possible explanations in the data, but nothing yet fully explains why homicides increased to 764 in 2016 from 485 in 2015, a 58 percent increase.
“We’re at the limits with the data we have right now,” Ludwig said Tuesday night.
He said the spike in homicides happened so suddenly and profoundly at the beginning of January 2016 that it helped rule out a lot of possible causes, but has offered few answers to researchers.
“You did not see it coming and then it happened instantaneously,” Ludwig said. “You can take a lot of the candidate explanations off the table because the timing doesn’t fit.”
He said researchers have honed in on a set of possible explanations, including real limits on the number of people police can charge with murder in a single year.
“One system that seems overwhelmed is the police’s ability to arrest people for shootings,” Ludwig said.
Homicide and shooting arrests remained steady as the number of incidents spiked dramatically in 2016, according to the report.
The clearance rate, or the number of murder cases police consider closed, dropped dramatically in 2016 to 26 percent from 36 percent in 2015, according to the report. That is down from a high of 46 percent in 2013.
The number of shooting cases that are cleared by police is also half of what it was in 2013, dropping to just 5 percent in 2016 from a high of 11 percent in 2013.
“If the clearance rate is going down, it increases people’s belief that they need to take matters into their own hands,” Ludwig said.
He said more people shooting others and going unpunished could also have super-charged a system of violent retribution that supersedes the justice system in many parts of the city.
Police are blaming the violence on a lack of fear of the justice system.
“The violence in 2016 was driven by emboldened offenders who acted without a fear of penalty from the criminal justice system,” Police Supt. Eddie Johnson said in a statement on Jan. 2. “The challenge we face as a city is serious, and like other cities it is significant. We will be adding to our police department, we are committed to partnering with residents, we will benefit from the investments being made by the mayor, and if we come together and work together I know we can turn the tide in 2017.”
Johnson has asked lawmakers frequently to increase the penalties for people committing gun crimes.
But the crime lab report shows that the number of street stops by police dropped dramatically at the same time homicide rates spiked. Police stops dropped by 80 percent to 10,000 per month in 2016 from an average of 50,000 per month in 2015, according to the report. The result was arrests dropped by 24 percent, mostly for drug crimes, between 2015 and 2016.
Ludwig said the timing fits and it lines up nicely with narrative that officers were so demoralized by criticism after the release of a video tape showing Laquan McDonald being shot by police that they stopped making arrests. But he said New York City went through a similar drop in arrests and never saw the spike in shootings and homicides that Chicago experienced.
Ludwig said there are other possible explanations, including some still unknown and sudden change in the structure of gangs in the city.
He said there are other things that, while unlikely, have not fully been researched, like stresses on the medical system from so many shootings becoming so severe that otherwise survivable injuries became fatal.
Ludwig said whatever the reason, discovering the cause does not stop the city from finding a solution.
“The solutions don’t need to be the reverse of the cause,” Ludwig said.
The full report is available online.
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