In this issue of JAMA Internal Medicine, Kagawa and colleagues report on their study of criminal convictions among nearly 80 000 individuals who legally purchased handguns in California between 2001 and 2013. The study’s findings suggest that legal firearm purchasers with a prior conviction for driving under the influence (DUI) of alcohol had an increased risk of subsequent arrest for violent crimes compared with purchasers with no prior criminal history. Research that explicates the criminal offenses of firearm holders, both legal and illegal, may increase understanding and help reduce firearm violence in the United States, a nation with more firearms in civilian hands than the next 25 nations with the highest totals combined.