Protesters attend a candlelight vigil in Fairfax, Virginia for victims of the Uvalde and Buffalo shootings on May 25.

Allison Bailey/Reuters Connect

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Allison Bailey/Reuters Connect

Protesters attend a candlelight vigil in Fairfax, Virginia for victims of the Uvalde and Buffalo shootings on May 25.

Allison Bailey/Reuters Connect

Every mass shooting in the United States sparks calls for better policies to prevent such tragedies. There is evidence to suggest that certain types of laws can reduce deaths from mass shootings, say scientists who study the field – but these policy options are not the ones typically discussed in the wake of these events.

The body of researchers to draw from is limited, notes Michael Anestis, executive director of the New Jersey Gun Violence Research Center at Rutgers University. “Mass shooting research is only a very small part of gun violence research,” he says.

It’s because the mass shootings represent less than 1% of the approximately 40,000 people killed each year by firearms in this country, says Anestis. “They’re horrible, they’re all too common, and yet, that’s just the tip of the iceberg, isn’t it?”

Researchers studying gun violence tend to focus on the types of violence, such as suicide, associated with the greatest number of deaths, he says, but he adds that the whole field of gun violence research has a long history. been neglected and barely funded.

“There’s money out there, but it’s really way below where it should be given the number of injuries and deaths and the economic costs associated with gun violence,” Anestis says. “It’s just disproportionately underfunded.”

Still, some studies have conclusions about what might prevent mass shootings.

One such study took advantage of the fact that in the United States, gun laws vary from state to state. “It’s, honestly, far from ideal from a public safety perspective, but it does provide opportunities for researchers,” says Daniel Websterco-director of the Johns Hopkins Center for Gun Violence Solutions.

He and a few colleagues have recently analyzed over 30 years of data on shootings in the United States that have resulted in four or more victims. They compared states to try to disentangle the effect of various gun laws. “I have to admit that this is really difficult and frankly inexact science,” says Webster.

Despite these limitations, he says, “we found two policies that had significant protective effects in reducing fatal mass shooting rates.”

One was the requirement that a gun buyer go through a licensing process. “A licensing process requires someone, you know, to apply directly and engage with law enforcement, sometimes there’s security training and other requirements,” Webster explains.

Another approach that appeared to reduce deaths from mass shootings was the banning of states from purchasing high-capacity magazines or ammunition feeders for semi-automatic weapons.

This makes intuitive sense, Webster says, because these objects allow a shooter to fire many bullets in a short time without interruption. If a shooter has to stop and reload, victims could escape or fire back.

Another study on mass shootings shows that this type of law seems to have a protective effect. David Hemenwaydirector of the Harvard Injury Control Research Center, worked with colleagues to examine the effect of banning high-capacity magazines over nearly three decades of mass shootings in different states.

“States that had bans did much better in terms of having fewer mass shootings, and the mass shootings that took place were much less lethal in terms of the number of people who died,” Hemenway said.

In the aftermath of a mass shooting, people often argue for the need for comprehensive background checks, Webster says. He supports this policy, but says his research does not show it is linked to a reduction in this particular type of fatal event.

An additional common refrain after a mass shooting, he says, is a call for policies that make it easier for people to carry guns so they can defend themselves. “Well guess what, the data doesn’t back it up at all,” Webster says. “If anything, it shows higher rates of fatal mass shootings in response to weaker regulations for concealed carry by civilians.”

And while school systems might try to respond to the threat of mass shootings by having police on site or involving students in drills, “as far as I know, there is no extensive research on those things,” Hemenway said.

Keeping guns away from young people, whether through safe gun storage in a home or age restrictions on purchase, should have a protective effect, Webster says, based on data showing that “the maximum age for violent offenses with firearms is roughly 18 to 21.”

The public health risks associated with alcohol consumption by young people inspired a ban on drinking before the age of 21, he says. But the Uvalde shooter was able to legally purchase semi-automatic rifles right after his 18th birthday.

It seems plausible that age restrictions make it harder for young adults to access weapons capable of creating a mass shooting, says Anestis, but “do we have great data-based resources to evaluate these policies? No, we don’t.”

An emerging policy option that is backed by preliminary evidence is to allow police to temporarily remove firearms from people who appear to be in imminent danger. A study in california who examined how this process was used over a two-year period in that state found 21 occasions when it was done in response to mass shooting threats – many of these threats involved schools.

It’s unclear whether removing these weapons actually prevented mass shootings, but the researchers say it’s still important data given the general lack of information and limited funding for the research. A study in 2017 found that guns killed about as many people each year as sepsis, a life-threatening response to infection, but funding for gun violence research was about 0.7% of that for sepsis.

“There’s so much to study in firearms, and we haven’t had enough study for 25 years,” Hemenway says. “Once you scratch the surface right now of what is known, we know so little.”