For the past 30 years, Detroit has struggled to contain a persistent homicide problem. Since 1990, the earliest year for which reliable data exists, the city’s murder rate slipped below the country’s top five only once. The year was 1996, and Detroit ranked sixth.

The vast majority of Detroit’s violence scars the city’s East and West Sides. In 2013, the Detroit Police Department decided to tailor its response to these hot spots with an evidence-based intervention called focused deterrence, in which police use data to directly intervene with people at a high risk for involvement in violent crime. Detroit’s focused deterrence strategy is part of a national program called Ceasefire.

Officers using this intervention partner with social workers and parole officers to arrange call-ins with at-risk people, where they emphasize the legal and lethal risks of criminal behavior, and steer them to social service programs like GED courses and job training.

A study published last week in the journal Crime and Delinquency by Giovanni Circo, a professor of criminal justice at the University of New Haven, and Julie Krupa, Edmund McGarrell, and Alaina DeBiasi, all criminologists at Michigan State University, examined Detroit’s effort over its first three years — and found new evidence for its efficacy.

What did it find?

The study’s authors tried to answer a central question: When a city implements a focused deterrence program like Ceasefire, does it deter criminals from committing crime, or simply force them to move their operations elsewhere?

They found evidence that people involved in call-in meetings in the first three years of Detroit’s program were 30 percent less likely to be re-arrested for any sort of crime for up to three years. The intervention had an even stronger effect on violent criminals, who were roughly 47 percent less likely to be re-arrested for violent crime.

“This was fairly credible evidence that these programs are effective, on average, at reducing the recidivism rate of criminals,” Circo said.

That’s great, but haven’t activists been arguing for less police involvement to reduce crime?

Some have. But interestingly, the end goal of focused deterrence interventions is actually fewer arrests, not more. Before adopting the strategy, the Detroit Police Department used a tactic known as a saturation patrol, in which officers flood neighborhoods in an attempt to deter criminal activity.

But saturation patrols had an unintended, if not predictable effect, exacerbating already fraught relationships between police and the city’s black community. This tension flared most notably in the 2010 killing of 7-year-old Aiyana Stanley-Jones.

Call-ins and other associated interventions, by contrast, are preventative in nature. They work by intervening before people commit crimes, thereby keeping them out of the criminal justice system.

Is there evidence that focused deterrence works elsewhere?

Yes. Since the late 1990s, cities across the country have implemented variations of the Ceasefire program, often to great success. In Oakland, for example, the city’s Ceasefire initiative reduced gun-related homicides by 30 percent in a five-year span between 2013 and 2018.

A wide body of research has found similar evidence in other cities, almost always measuring the program’s efficacy against corresponding citywide reductions in crime. But until Circo and his colleagues’ study, few researchers had examined the program’s effect on people. Their study suggests participants themselves are less likely to be re-arrested.

Has focused deterrence made a dent in Detroit’s persistently high murder rate?

The answer is unclear. In 2017, the city’s homicide rate hit a 30-year low, and held steady the following year. But at 39.9 homicides per 100,000, the rate still ranks in the country’s top five.

That said, fatal and nonfatal shootings have dropped in a number of precincts where the city’s Ceasefire program is active. This success may be obscured citywide by the number of precincts without an active Ceasefire effort ongoing.

In the absence of a sizeable citywide effect to demonstrate the program’s efficacy, the new study provides a next-best argument for expanding Ceasefire to the rest of Detroit. The police department has already taken tentative steps to that end: In 2015, it expanded the program to the city’s West and Northwest Sides, according to Circo. He added that the department has also applied to renew the grant used to fund his research.

“As they slowly roll this all out, we’re going to be thinking about whether the size of the program will affect our findings,” Circo said. “How does this scale on a whole city level?”