Researchers find little evidence military policing reduces crime

A team of researchers led by Brown University Associate Professor of Political Science and International and Public Affairs Rob Blair studied a crime intervention in Cali, Colombia, and found little evidence to support the idea that military policing reduces crime.

The debate around deploying armed forces for domestic policing operations in high-crime areas is often framed as a trade-off between public safety and civil liberties. But in a recent study led by Rob Blair, an associate professor of political science and international and public affairs at Brown University, researchers found little to no evidence to support the notion that this tactic improves public safety and only limited evidence of increased human rights abuses.

In a paper published in Nature Human Behaviour the research team — which also includes Associate Professor Michael Weintraub from the School of Government at Universidad de los Andes in Bogotá, Colombia — argues that "the benefits of military policing are probably small and not worth the costs."

A controversial but common practice

Proponents of military policing argue that it effectively reduces crime, while opponents claim it leads to more human rights abuses. Until now, due to a shortage of rigorous studies on the topic, there has been little evidence to support either position. The authors note that, to date, "arguments on both sides of this debate remain almost entirely anecdotal and impressionistic."

Blair said using military forces to police high-crime civilian areas is relatively common in Latin America. "If you travel to almost any country in Latin America, you will see soldiers performing tasks that, in the U.S., we would typically associate with police officers. Things like running patrols, interrogating suspected criminals, setting up roadblocks, et cetera," he said, "it's very common, and it's very controversial."

Given the ubiquity of the practice, and the lack of controlled studies to support its effectiveness, Blair and Weintraub partnered with the mayor's office, Colombian armed forces and Innovations for Poverty Action Colombia to evaluate the impact of a military policing intervention in Cali, Colombia, one of the country's most violent cities.

A violent city

In 2018, Cali had a homicide rate of 46.7 per 100,000 residents, more than triple that of the capital of Bogotá. In an effort to reduce crime, the government developed a program — Plan Fortaleza — that involved recurring, intensive military patrols targeting high-crime areas in the city. Blair noted that Cali's security and justice secretariat reached out to Weintraub "to see if he would be interested in setting up an impact evaluation of this intervention that they planned on running."

According to Blair, both the city and the military were highly supportive of their work and interested in evidence-based approaches to crime reduction. "They were convinced that we would find this approach effective," he said, "they thought a rigorous evaluation would give them ammunition — so to speak — to argue that the way they do policing is effective."

Upon examining the data, however, the research team found "little to no evidence" that military policing reduced crime during the operation. "We didn't see any reduction in crime and, if anything, we saw an increase in crime after the intervention was over," Blair said. "That was quite surprising," he added, "I thought — whatever the effects on human rights or citizen attitudes toward the military — we would see evidence of crime reduction. But we didn't."


Blair compared the study's methodology to a randomized medical trial. "We randomized which particular city blocks were going to get patrolled and which ones weren't over the course of this intervention," he said. "Just like in a drug trial where you randomize who takes medication and who doesn't, we randomized the military patrols to measure if they were truly effective." 

The research team's approach to the question of the intervention's effectiveness was rigorous. Blair said, "This was probably the most ambitious data collection effort I've ever undertaken." "Crime data is often pretty noisy, especially in lower-income countries," he said, "a lot of crimes go unreported." But Blair noted the city was able to provide the research team with a large amount of high-quality data because the mayor's office regularly meets with the police, the coroner's office and other local officials to try to capture the true prevalence of violent crime in the city.

In addition, the research team ran two surveys, one during the intervention and another after it. "Those surveys reached about 10,000 residents in total," he said. "We also had civilian monitors with the soldiers at all times, monitoring and helping them navigate to the particular blocks they were supposed to patrol. And those monitors recorded their observations of what was going on. So we have really nice data on where the patrols actually went, how long they spent at each location and what the soldiers did while they were there," he said.

Future research

Blair said he hopes this publication will lead to further rigorous studies that grow the evidence base on the effectiveness of military interventions in civilian areas. "Currently, there is a slim body of work that addresses this question which is why I'm really proud of this study," Blair said, "it was a lot of work, and we collected a huge amount of data. I'm happy to see it in print."