"California's ban on handgun sales to criminals convicted of ‘violent misdemeanors’ has significantly reduced the risk of repeat arrests for violent crimes, according to an analysis by the University of California at Davis." – San Francisco Chronicle, Feb. 28

The above statements were written in response to a study published by the Journal of the American Medical Association (JAMA) that examined the effectiveness of a 1991 California law prohibiting gun purchases by those who had been convicted of misdemeanor offenses. The study compared the arrest rate of those "misdemeanants" who had their handgun purchases approved before the law went into effect to those who were denied purchase after it was passed. According to the Chronicle, the journal's contributing editor, Dr. Thomas Cole, stated in an editorial accompanying the study that it provides "solid evidence" that the limits on handgun sales to those convicted of violent crimes prevents subsequent violence. "Unless better evidence proves otherwise, this intervention works," said Cole.

Finally, a gun control policy that works! Well, maybe. The following are excerpts from an article on the Statistical Assessment Service (STATS) Website that examines the results of the study from a medical research standpoint (STATS is a nonpartisan, nonprofit research organization in Washington, D.C., devoted to the accurate use of scientific and social research in public policy debate.) The article suggests that "once proper medical standards are applied in interpreting such research, the evidence often seems less convincing from a medical standpoint, than it does from a criminological point of view."

"…The first issue is whether someone who was allowed to purchase a gun is at a significantly greater risk of committing a crime compared to someone who was denied purchase. Doctors measure such things using ‘relative risks.’ These risks are measured by odds ratios, and the study found an odds ratio of 1.15:1 for the handgun purchasers. This means that for every 100 people not allowed to buy a gun but who nevertheless committed a crime, 115 people who had been allowed to do so broke the law. Relative risk is a tricky area in medical science, because it is hard to filter out other factors that may affect the result. Epidemiologists are therefore loath to consider small relative risks as indication of any strong link between the disease and the possible cause."

"A relative risk of 1.15 is very small and would therefore be ignored by experts. The study’s authors did so, to their credit. What they considered significant, however, was the relative risk for committing gun and/or violent crime specifically, which they calculated at about 1.3:1. But even a 30 percent greater risk like this would be regarded as minuscule by epidemiologists. In fact, they normally require a difference of 200-300 percent before concluding that they have evidence of cause and effect (the relative risk for lung cancer among smokers, for instance, is roughly 30:1). The relative risk at issue here does not meet the medical standards for real concern about cause and effect. Therefore the claim that it is the handgun purchase that makes the difference cannot be made with any real certainty."

"Furthermore, when an epidemiologist looks at the cause of a disease and discovers a slightly elevated risk among, say, left-handed people, he does not stop there. He looks further and asks whether it affects all left-handed people or predominantly left-handers with bad eyesight, for example. Most left-handers could actually be less susceptible to the disease, but the overall risk for the group as a whole could be increased by the disproportionate effect in the sub-set of myopia sufferers. Was there such a disproportionate effect in this study?"

"There certainly seems to be. The researchers split the ‘risky’ population—the ‘misdemeanants’ who had gotten guns and then committed crimes—into about 30 sub-groups, depending on age, number of prior convictions, and number of prior convictions for gun and/or violent crime. Of these, only three groups came out with relative risks enabling the researchers to say with any confidence that they would be more likely to commit crimes. They were ‘misdemeanants’ arrested for gun and/or violent crime who were either aged 30-34 (a relative risk of 1.64), who had had four or more prior convictions of any sort (a relative risk of 1.8), or who had been convicted for one gun and/or violent crime previously. (Interestingly, more prior convictions for these crimes meant less of a chance of arrest.) All the other sub-categories possessed either an approximately equal or lesser chance of arrest."

"These findings seem pretty clear. They point to a conclusion that habitual minor criminals are more likely than others to commit gun and/or violent crime. It is also important to bear in mind that ‘gun and/or violent crime’ need not necessarily involve a firearm—a drunken bar fight would qualify just as much as armed robbery. The role of legal gun purchase in leading to such an eventuality is far from clear (in epidemiological terms, there is no ‘biological pathway’ here)."

"From the evidence the researchers uncovered, then, it might actually be possible to argue that the California law forbids many people handgun purchase for no reason. Given that certain categories of former offenders are shown to be less likely to commit crime when allowed access to firearms, the evidence could be interpreted as demonstrating that allowing such people access would be a useful public safety measure. Still, such a conclusion would be just as shaky as the conclusion that the law reduced crime."

"If the role of guns in violence is to be examined from an epidemiological standpoint, the rigorous standards normally used in that field must be followed. Drawing conclusions that cannot stand up to detailed scrutiny does not necessarily help advance the cause of public safety."

More Lies, Damned Lies