Stop and Frisk policies are controversial because of claims of racial bias in implementation.

In August 2015, the ACLU and the Chicago police department reached a consent agreement to scale back stop and frisk. The ACLU-Illinois website describes the accomplishment:

In August of 2015, shortly after the ACLU released a groundbreaking report, the ACLU of Illinois and the Chicago Police Department (CPD) reached a landmark agreement to reform the practice of investigatory street stops known as “stop and frisks.” The City agreed to take steps to ensure that CPD policies and practices comply with the Fourth Amendment, which protects against unreasonable searches and seizures, and the Illinois Civil Rights Act, which requires that government policies do not have a racially disparate impact.

The result was a dramatic decline in stops, as this February 1, 2016 local ABC News story reported, CPD “stop and frisks” down 80 percent in 2016:

As shootings and murders spike one major component of Chicago police crime fighting is way down. The number of street stops by officers has plunged 80 percent this year.

For decades when Chicago police stopped and frisked someone on the street, they had to fill out a small card called a “Contact Card.” It required simple, basic information about who was stopped and why. Beginning January 1, 2016, a new state law regulated when cops could stop and pat down people in public and then officers had to fill out a two page “Investigatory Stop Report.”

“From May through August of 2014, there were 250,000 people who were stopped who were completely innocent; who committed no crime, who were not guilty of any offense. We know that most of those people are searched. If that number is going down, that’s really good news,” says Ed Yohnka of ACLU-Chicago.

The number of street stops by Chicago police has almost bottomed out. In police ranks, this is known as the “ACLU effect,” after American Civil Liberties Union lawyers fight for years to curtail Chicago officers from what they saw as illegal stops.

Two academics decided to study the effect on violent crime and homicides after the reduction of stop and frisk policies in Chicago. They round found that the scaling back led to hundreds of additional deaths.

The authors of the study were U. Utah law professor Paul G. Cassell and economics professor Richard Fowles. Cassell summarized the findings in a post at Volokh Conspiracy, The 2016 Chicago Homicide Spike – Explained. The sub-headline provides the topline conclusion: “After an ACLU consent decree with the Chicago Police Department dramatically reduced the number of stop and frisks, homicides significantly increased as a result.”

Here’s an excerpt:

Through multiple regression analysis and other tools, we conclude that an ACLU consent decree trigged a sharp reduction in stop and frisks by the Chicago Police Department, which in turn caused homicides to spike. Sadly, what Chicago police officers dubbed the “ACLU effect” was real—and more homicides and shootings were the consequence.

The analysis is relatively straightforward. It is well known that homicides increased dramatically in Chicago in 2016. In 2015, 480 Chicago residents were killed. The next year, 754 were killed—274 more homicide victims, tragically producing an extraordinary 58% increase in a single year….

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….

We conclude 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.

https://reason.com/volokh/2018/03/26/the-2016-chicago-homicide-spike-explaine

The 96-page analysis is here (pdf.) and provides a wealth of information and charts, with a full explanation of methodology.

The Chicago Tribune reports on the study, and the pushback:

But the ACLU and several crime experts who reviewed the study at the Tribune’s request questioned its findings.

“They’re more or less suggesting that working in an unconstitutional police department is worth the trade-off,” said John Eterno, a criminal justice professor at Molloy College in Rockville Centre, N.Y., and a former captain with the City of New York Police Department. “If you’re going to be doing 40,000 stops a month … you have to have reasonable suspicion on every one of those 40,000 stops.”

Karen Sheley, an ACLU staff attorney who is overseeing the agreement with Chicago police, dismissed the study as “junk science.”

“This particular viewpoint is both insulting to officers who follow the law on a regular basis and ignores the harm, including the public safety, to the communities who are most impacted by police work,” she said…..

In perhaps their most controversial conclusion, Cassell and Fowles ruled out as a factor in the heightened 2016 violence the court-ordered release of dashboard camera video of a white Chicago police officer shooting Laquan McDonald, a black teen, 16 times.

The video, released in November 2015, rocked the Police Department, prompting weeks of street protests, the firing of police Superintendent Garry McCarthy, first-degree murder charges against Officer Jason Van Dyke and a yearlong U.S. Department of Justice investigation that found officers had routinely violated the rights of minorities for decades.

But Cassell and Fowles argued that the McDonald shooting had gained attention months before and wasn’t as timely a factor in the spike in violence in 2016 as the ACLU agreement going into effect at the beginning of that year.

“Awareness that Officer Van Dyke had done something terrible was widespread much earlier – such as in April 2015 when … Chicago’s City Council voted to pay $5 million to McDonald’s family,” the study said. “Nor did the video’s release constitute a unique revelation of possible racism by some Chicago police officers.”

But critics faulted the report for ignoring the broad impact of the McDonald video while singling out only the ACLU agreement.

“To minimize the impact of that video is really a mistake,” said Edwin Yohnka, the ACLU’s longtime spokesman in Chicago.

The professors analysis of the impact of the Laquan McDonald shooting starts at page 35 of the full report (linked above).

While the Laquan McDonald video was shocking—and led to significant backlash against the CPD and the mayor—we think it is an unlikely candidate to explain the Chicago homicide spike. To be sure, an argument can be made that the date of the video’s release (November 24, 2015) fits the subsequent increase in homicides and shootings that we observed. As noted earlier, there is a breakpoint in our homicide and other series around November 2015. But as the events recounted above make clear, awareness of Officer Van Dyke’s actions and rumors of a coverup was widespread much earlier—such as in April 2015 when a unanimous Chicago City Council voted to pay $5 million to McDonald’s family.

More important, a causal mechanism through which the video’s release triggered the homicide spike is not immediately obvious. The protests that surrounded release of the video concerned alleged racism by the CPD in shooting a young African-American man sixteen times. It is unclear why a result of such events would have been additional shootings of (predominantly) young African- America men by (predominantly) other young African-American men. Nor did the video’s release constitute a unique revelation of possible racism by some of Chicago’s police officers. Sadly, CPD has a long history of allegations of racism—including widely-publicized allegations preceding the 2016 spike. [footnotes omitted]

But let’s say the McDonald video did make police more hesitant to stop and frisk and police. That might let the ACLU somewhat off the hook, but it wouldn’t change the overall point, that police hesitation leads to increased crime.

Yet the clamp down on Chicago stop and frisk is being hailed as a success, as this recent Chicago Sun-Times article reports, though the focus still is on race:

The Chicago Police Department has “come a long way” to alleviate the concerns of civil rights activists about officers stopping minorities for questioning, a retired federal magistrate judge said in a report released Wednesday.

Arlander Keys is studying cops’ stops under an agreement that took effect on Jan. 1, 2016 between the department and the American Civil Liberties Union. The ACLU had criticized the police for disproportionately stopping minorities and failing to list lawful reasons for stops on the “contact cards” they were supposed to fill out.

In his latest report, Keys said he was unable to determine — or rule out — that the department’s stop-and-frisk policies and practices have an unlawful, disproportionate impact on racial and ethnic minorities.

But he said he was encouraged that in a sample of the 51,000 stops he examined from July to December 2016, cops “conducted an overwhelmingly large number of legitimate, lawful and justified stops.”

Officers did fewer “protective pat downs” of people they believed might be carrying weapons, Keys said. And a bigger percentage of those pat downs yielded weapons than during the first six months of 2016, which he previously studied. White people were the smallest group subjected to those pat downs, but were the most likely to have weapons on them.

Keys said the racial breakdown of the 51,000 stops in late 2016 painted a “less rosy picture.” About 70 percent of those stopped were black, 19 percent were Hispanic and 1.5 percent were white, he said.

Certainly the police should not racially discriminate. But the clamp down on stop and frisk appears to have its own racially discriminatory impact, as gun violence among gangs takes an increasing toll on the black community in Chicago.