This photo of Ieshia Evans meeting police in full riot gear in Baton Rouge, Louisiana, went viral in 2016.
This photo of Ieshia Evans meeting police in full riot gear in Baton Rouge, Louisiana, went viral in 2016. Jonathan Bachman/Reuters

Recent research shows that not only are militarized squads used disproportionately in communities of color, but contrary to claims, they reduce neither crime nor police injury or death.

After a police officer killed 18-year-old Michael Brown in 2014, Ferguson erupted. One image from the unrest shows the silhouette of a solitary man standing with his hands up in front of a row of armored vehicles, eliciting comparisons with the “tank man” from the Tiananmen Square. In another image—this time from the Baton Rouge, Louisiana, after the shooting of Alton Sterling in 2016—a woman stands serene, while two police officers in heavy-duty gear approach her.

For many Americans, it is perhaps in these moments that the extent to which local police departments have militarized became evident. Law enforcement have often requested military-grade equipment in the aftermath of police shootings, arguing that these weapons protect them and increase public safety; whereas critics have argued that they will further strain trust between the police and communities, making bad situations much worse.

So which is it?

A comprehensive new study published in the National Academy of Sciences provides some answers. For it, Jonathan Mummolo, a professor of politics and public affairs at Princeton University, used a public records request to obtain data on every SWAT (Special Weapons and Tactics) deployment in Maryland, information that had been recorded due to a state statute.

Upon analyzing it, he found a strong correlation between SWAT deployments and the share of black residents in a locale, even after controlling for crime rates, and other social and economic characteristics of the place (unemployment, education, household income). A 10 percent increase in the percentage of black residents in a neighborhood is associated with a 10.53 percent increase in SWAT deployments per 100,000 residents during the time period he examined. Around 90 percent of times, the SWAT officers were deployed to serve a warrant. These results from Maryland “are consistent with the descriptive claim that Black residents face a pronounced risk of experiencing militarized policing,” Mummolo writes in the report.

Next, he tackled a claim often cited by proponents of higher militarization: that more military grade weapons are beneficial because they help avert violent crime and ensure the safety of police officers. This was the rationale given when the Trump administration walked back an Obama-era rule limiting the transfer of military equipment to local police in 2017.

“Those restrictions went too far,”Attorney General Jeff Sessions said in a speech at the time. “We will not put superficial concerns above public safety.”

To test that theory, Mummolo uses a combination of data sets with information on the location of 9,000 law enforcement agencies that have SWAT teams, and finds, well, nothing: “I find no evidence that obtaining or deploying a SWAT team reduces local crime rates or lowers the rates at which officers are killed or assaulted.”

Third, he takes a stab at sussing out the psychological effects of seeing officers in heavy military gear through survey experiments. When shown images of heavily geared-up officers versus those who are in ordinary police uniform, respondents tended to support the former less. (The survey sample contained a larger share of African Americans, because this group is more likely to see SWAT teams.) Mummolo concludes:

“These results suggest that the often-cited trade-off between public safety and civil liberties is, in the case of militarized policing, a false choice.”

Edward Lawson Jr., a researcher at the University of South Carolina, also finds detrimental effects of police militarization in his recent research. He uses the receipt of surplus military equipment as a measure for police militarization, and finds that where militarization increased, so did deaths of suspected civilians. In a blog post on the London School of Economics U.S. Center site, he writes:

Militarized police departments see themselves not as public servants upholding the law, but as an army fighting a war against a dangerous and invisible enemy and occupying territory that is hostile to them. To carry out these actions, the leaders of those departments desire military equipment—vehicles, weapons, body armor, and so forth—because it provides better protection from the enemy and promotes both more efficient use of force and more fear among the public. And, when departments are more militarized, their officers should kill more people.

Both researchers stress that militarization entails more than the equipment and tactics. Mummolo’s analysis focuses on SWAT deployment for most part, but to him, militarization is about “a culture that centers on violent conflict.” Lawson describes it similarly, as a “psychological process” that condones, and even encourages violence, as the solution. That’s important when considering the efforts of many cities to demand public oversight over their local police department’s desire for shiny new guns.

Even if they succeed in limiting the BearCats, MRAPs, M4 rifles, and LRADs, it’s not clear that the culture of militarization and using violent force is likely to shift any time soon.

CORRECTION: An earlier version of this article noted that Edward Lawson Jr., was a researcher at University of Southern California. He’s at the University of South Carolina.

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