Molly Redden dismantles the work of John Lott, a major advocate of concealed-carry laws:

Lott’s research, as the title of his book suggests, is dedicated to proving that more guns in more hands reduces violent crime. In the wake of Newtown, that means guns in teachers’ hands, and an end to the gun-free zones that he says make schools "a magnet for these attacks." But Lott’s research has always been problematic. For starters, he's a lousy data analyst. Lott allowed Professors Dan Black and Daniel Nagin to reevaluate his data for their 1998 inquiry into the effects of concealed-carry laws on violent crime rates. Their findings, published in the Journal of Legal Studies in 1998, blew a hole in his: "Our reanalysis of Lott and [co-author David] Mustard’s data provides no basis for drawing confident conclusions about the impact of right-to-carry laws on violent crime,” they wrote. "As a result, inference based on the Lott and Mustard model is inappropriate, and their results cannot be used responsibly to formulate public policy." Four years later, Ian Ayres of Yale and John J. Donohue III of Stanford Law gave his scholarship an even more vicious debunking. (Media Matters summarizes the many challenges to his research here.)