Fact check: Would Dianne Feinstein’s assault weapons ban stop future mass shootings?

U.S. Sen. Dianne Feinstein renewed her call Monday to reinstate a federal assault weapons ban and cited data that said an expired one was effective.

“We have to get weapons of war off our streets,” Feinstein said in a statement, her fourth on gun violence following three mass shootings over the past week.

Feinstein, who wrote a 1994 federal law that banned so-called assault weapons for 10 years, pointed to data compiled by author Louis Klarevas, who found that gun massacres dropped by 37 percent during the decade the law was in place.

“But the decade after the ban expired saw an enormous 183 percent increase in massacres,” she noted in her statement.

That data on its own does not prove that the ban on military-style rifles and other semiautomatic firearms is the singular cause for the drop in mass shootings. Nor does it demonstrate that the ban’s lapse in 2004 — thanks to a sunset clause in the law — directly drove an increase in shootings.

Other factors could also be at play, such as the copycat effect one shooting has on other potential shooters.

And the academic research on the effects of the federal assault weapons ban on mass shootings is limited.

A 2015 study found a statistically significant association between the federal assault weapon ban and reductions in mass shooting deaths and injuries, although the nonpartisan think tank the Rand Corporation, found that the study did not meet their standards of analysis.

The “evidence for the effect of assault weapon bans on mass shootings is inconclusive,” the Rand Corporation concluded in 2018.

The 2015 findings, however, were bolstered in a 2019 analysis of open-source data on mass shooting deaths. which found that “mass-shooting fatalities were 70 percent less likely to occur during the federal ban period.”

In other words, an assault weapons ban may not keep mass shootings from happening, but they could keep them from being so lethal.

An analysis by the pro-gun control group Everytown for Gun Safety last year found that “Mass shootings that involved the use of high-capacity magazines resulted in more than twice as many fatalities and 14 times as many injuries on average compared to those that did not.”

That is part of Feinstein’s argument for renewing her law, something the majority of Republicans in Congress have opposed.

“It took the Dayton shooter less than 30 seconds to shoot 35 people, nine of whom died,” she observed in her statement on Monday. “These weapons are designed to kill as many people as possible, as quickly as possible.”

As Feinstein, herself, acknowledges, the assault weapons ban would only address one part of the nation’s broader crisis of gun violence. As Vox noted in an article last year, “Shootings with rifles, including assault rifles, make up less than 3 percent of gun homicides” in the United States, while handguns represent more than 70 percent of the firearms used in homicides.

A new study published in March found that the three state laws that were most effective at reducing gun deaths were universal background check requirements, prohibitions on violent offenders purchasing guns, and restricting concealed carry permits.

In her statement, Feinstein said she supported universal background check legislation that has been passed in the House.

She also pointed out that she “introduced a bill in February that creates a grant program for states to set up their own extreme-risk protection laws,” something California has already passed. The law enables family members or law enforcement to petition a court to confiscate an individual’s guns, if they can prove the person is at risk of harming him or herself or others.

“That bill, with 27 cosponsors, received a hearing in March but hasn’t been voted upon,” Feinstein said. “The Senate could vote on that bill today.”

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Emily Cadei works out of the McClatchy Washington bureau, where she covers national politics and policy for McClatchy’s California readers. A native of Sacramento, she has spent more than a decade in D.C. reporting on U.S. elections, Congress and foreign affairs for publications including Newsweek, Congressional Quarterly and Roll Call.