Findings suggest implementing three state laws at federal level could reduce the rate of US gun deaths by more than 90%, but experts say it’s ‘not good science’

Implementing three state gun control laws at the federal level could reduce the rate of American gun deaths by more than 90%, a new study has found.

But leading gun violence researchers have called that result “implausible”, and said the study’s design is so flawed that some of its findings are not believable.

The paper, published in the British medical journal The Lancet and written by researchers at Boston University, Columbia University and the University of Bern in Switzerland, found that one of the three most effective gun policies were laws requiring ballistic imaging or microstamping, which help law enforcement identify guns used in crimes.

Experts noted that the laws, which were on the books in only three states, were not actually being implemented in practice.

That “would be the biggest red flag, obviously, when they’re finding huge effects of a law that doesn’t exist”, Daniel Webster, the director of the Johns Hopkins Center for Gun Policy and Research, said.

He called the paper’s approach “just not good science”.

While some of the paper’s findings are interesting, it’s “highly questionable” whether other results “are an accurate reflection of reality”, David Hemenway, a leading gun violence researcher at Harvard’s school of public health, wrote in a comment published along with the paper.

Bindu Kalesan, the paper’s lead author, defended its findings as important contributions to an extremely complex and difficult area of research. The criticisms of the paper were “expected”, she wrote.

When it comes to American gun laws, she said, “there are so many layers to this. Every time I remove one layer, there’s another layer.”

For instance, looking at whether the state laws that the study evaluated were actually being implemented was “another layer” beyond what the researchers chose to examine, she said. While further research is needed, she said, “what we’ve offered is a strong direction that we can go in”.

Kalesan, the director of the Evans Center for Translational Epidemiology and Comparative Effectiveness Research at Boston University Medical School, said the aim of the paper was to advance the troubled public policy debate on guns in America by sorting through the different state-level gun laws and identifying the few that had the greatest potential to reduce gun deaths.

The paper compared 25 different state gun laws and concluded that nine of them were associated with reduced gun death rates.

According to the study, the three state laws “most strongly associated with reduced overall firearm mortality” were universal background checks for gun purchases, background checks for ammunition purchases and “identification requirements for firearms”, such as ballistic fingerprinting and microstamping.

“If a law for universal background checks was implemented federal, overall firearm mortality could reduce from 10.35 to 4.46 per 100,000,” a 57% reduction, the paper concluded. Implementing all three laws at the federal level “could reduce national overall firearm mortality to 0.16 per 100,000”.

Other researchers who have published major evaluations of American gun laws said it was implausible that implementing three relatively modest gun restrictions could have such a huge impact on gun deaths.

“We’ve seen much more dramatic interventions in Britain and Australia and places like that, and even they did not get those kinds of results,” said Phil Cook, a public policy expert at Duke University who was one of the authors of a major study on the effectiveness of the nation’s current federal background check law.

Jeffrey Swanson, a Duke professor who researches the relationship between mental health and violence, said the study’s results left him “queasy”. Gun violence is simply too complicated, with too many different causes, to be fixed so easily, he said.

However Swanson and Webster agreed that they expected universal background check laws to help reduce gun deaths. That finding “may be real”, Swanson said.

Kalesan, the lead author, contested the idea that the dramatic drop in gun violence from three laws was implausible.



“Considering that there are as many guns in this country as there are residents, it is plausible that background checks for ammunition purpose may in fact markedly reduce the gun death rate,” she wrote in an email. She also noted that the researchers expected the effect would be a long-term one, “and thus will take several years to occur”.

The main problem with the Lancet study, other researchers said, was that it attempted to determine the effectiveness of state laws by comparing gun death rates of different states with different sets of laws. The study controlled for a handful of factors, including unemployment rates and levels of gun ownership in different states. It did not control for levels of poverty, race or how urban or rural a state was, all factors crucial to understanding levels of gun violence, other researchers said.

“There are too many things that make states different from one another, that explain their different rates of homicide or suicide, than the couple of variables that they look at,” Webster said.

Kalesan, the paper’s lead author, said they had purposefully built a “parsimonious model” and that controlling for poverty, for instance, was not essential since they were already controlling for unemployment, a similar social factor.

Other researchers said comparisons across states were simply too messy to isolate the effects of state gun laws, and that a better way to determine the effectiveness of gun laws was to look at changes in gun death rates over time, particularly before and after a given law was passed.

In his comment published with the Lancet paper, Hemenway noted that some of the paper’s general findings mirrored the results of previous research. Other studies have found an association between tough gun laws and lower rates of gun death. He wrote in an email to the Guardian that it was also interesting that universal background checks “continued to be associated with low levels of gun death even after controlling for other gun laws”, and that, more broadly, “in simple comparisons, every gun law was associated with lower levels of gun death and the one pro-gun law was associated with more gun death”.

But, Hemenway wrote, he did not believe that “any of the highly specific conclusions” of the study – such as the estimates of the dramatic reductions in gun death if the laws were changed – were “anywhere near accurate”.

“Most USA gun laws have been pretty minor and should have minor effects,” he wrote.

For some of the other findings, even the study’s researchers found the results perplexing. The paper found that several modest gun control laws were associated with an increase in gun death rates, including bans on assault weapons and laws requiring gun locks on firearms to protect them from being used by children.



“How could requiring firearm locks for child access prevention very significantly increase firearm related deaths? It defies logic,” Webster said. “How can assault weapon bans increase homicide rates when they are incredibly rarely used in homicides?

“You have to do some really bizarre mental gymnastics to explain what they’re seeing here,” he said.



In the study, the researchers wrote that the association between firearm locks and higher risk of gun death could be explained by another study that found child access prevention laws were associated with an increased likelihood of unsafe firearm storage.

One potential explanation for the association, Kalesan said, was that gun buyers in states where firearm locks were required for guns purchased from a licensed dealer might be more likely to buy guns from unlicensed dealers or on the illegal market.

Kalesan said the paper also found an association between firearm identification laws, designed to help trace crime guns, and lower risk of suicide. “I’m not sure why that would be the case,” she said. “This is a space where we need more study.”

The debate over the study comes in the midst of a continued controversy over funding for gun research. Democrats and President Obama have pushed Congress to restore gun violence prevention research funding at the Centers for Disease Control and Prevention, while Republicans have continued to oppose it.

“I hate to criticize the research on the effectiveness of firearms-related regulations. There needs to be more of it. There needs to be more research and more funding,” Swanson said. But the weaknesses of The Lancet study “are more serious than [the authors] seem to suggest”, he said.

Swanson said he worried that the disagreement over the study might be counterproductive. He said he was concerned that it might be used to inaccurately label some laws as ineffective, and that studying the effectiveness of firearms laws is too difficult to carry out. But this kind of research is possible, he said. “It just takes more time and effort to do it than this study did.”

“I can imagine a future in which we have very substantially lower gun deaths than we have, as much as 30 to 50% lower,” Webster said. But even with universal federal background checks, permit to purchase laws, and a set of other gun control policies, “It’s hard to me to imagine anything beyond a 50% decline,” he said. “That’s kind of a best case scenario.”

“This is an incredibly respected journal,” he said. “That is what’s so shocking to me. I’m really, really baffled about how this got in.”