State laws that allow private citizens to carry concealed weapons do not reduce crime and may even increase it, according to a study released Wednesday by the Brookings Institution.
The findings, by Stanford University law professor John Donohue, contradict an influential study by economist John R. Lott Jr., a research fellow at the American Enterprise Institute who in 1997 concluded that by adopting such laws, states can substantially curb violent crime.
Since the late 1970s, 33 states -- California is not among them -- have enacted "shall-issue" or "right-to-carry" laws, which require law enforcement authorities to issue handgun permits to qualified applicants. Among the states are Texas, Florida, Pennsylvania, Utah and Nevada.
But social scientists, represented on opposing sides by Donohue and Lott, remain stubbornly divided over the effect of such laws on crime rates.
"If somebody had to say which way is the evidence stronger, I'd say that it's probably stronger that the laws are increasing crime, rather than decreasing crime," Donohue said Wednesday in an interview. "But the stronger thing I could say is that I don't see any strong evidence that they are reducing crime."
Donohue's study, which builds on work with Ian Ayres, a law professor at Yale University, will appear in "Evaluating Gun Policy," a book to be released by Brookings this month.
The book also includes a separate study by Philip J. Cook and Jens Ludwig, professors at Duke and Georgetown universities, who conclude that gun ownership may actually increase the risk of being burglarized in the United States.
Donohue's study will also be published in the May issue of the Stanford Law Review -- side by side with an updated study by Lott, who defends his position and rejects Donohue's findings.
Though they differ in methodology, both studies attempt to account for outside factors that may influence crime rates.
For his part, Donohue said that right-to-carry laws may deter violent crimes, such as murder or robbery, in some situations, while encouraging them in others.
For example, he said, an attacker may wrest control of a handgun away from a victim, who may be less experienced in handling firearms, and use it against the victim.
Also, otherwise law-abiding citizens may become "emboldened to do bad things, some of them violent" in the heat of the moment, Donohue said.
By contrast, Lott -- whose position is summed up in the title of his 1998 book, "More Guns, Less Crime" -- says that in states with right-to-carry laws, criminals are more wary of armed citizens who are prepared to defend themselves.
In his original study, published in the January 1997 issue of the University of Chicago's Journal of Legal Studies, Lott and David Mustard, an economics professor at the University of Georgia, contended that the 10 states that adopted right-to-carry laws from 1985 to 1991 experienced substantial declines in murder and other types of violent crime, compared with states without such laws.
Calling those conclusions "deeply flawed" and "misguided," Donohue said that his study revealed the opposite. According to his research, 13 states that enacted right-to-carry laws after 1992 experienced steep increases in murder and other violent crime rates, compared with states without such laws. His findings are based largely on a new analysis of the 1977-96 crime statistics originally presented by Lott and Mustard, along with new data from 1997.
In his Stanford Law Review article, Lott counters that "Ayres and Donohue have simply misread their own results....The most detailed results that they report ... show large drops in violent crime" right after the laws are adopted.
A comparison of crime trends in adjacent counties in two states -- one with a right-to-carry law and one without -- demonstrates "a drop in crime rates in the areas with the law and an increase in those without the law," Lott said.
But Donohue argues that such comparisons are generally skewed, since the states that have adopted such laws tend to be rural and relatively isolated from the types of violent crime -- such as offenses related to crack cocaine -- that disproportionately affect more urbanized states, many of which have not enacted similar laws.