Do guns make people safer or more susceptible to violence? Does banning assault-style weapons or expanding background checks save lives, or are such measures merely inconveniences for law-abiding gun owners? These are just some of the questions in the debate over gun control, with advocates and foes lobbing a dizzying number of statistics and studies to make their case. Often, those facts and figures contradict one another. The lack of objective research on gun violence has become evident as Minnesota and the nation grapple with a slew of proposed changes to gun laws after the Newtown, Conn., school shooting that...