Earlier this week, just hours before the first presidential debate in Denver, Aurora shooting victim Stephen Barton spoke out in a new ad put out by  Mayors Against Illegal Guns, asking the voters to pay close attention to how both candidates addressed gun violence. "This past summer in a movie theater in Colorado, I was shot – shot in the face and neck – but I was lucky," he says. "In the next four years, 48,000 Americans won't be so lucky, because they'll be murdered with guns in the next president's term. Enough to fill over 200 theaters. So when you watch the presidential debates, ask yourself, 'who has a plan to stop gun violence?'" If you listened to the  debate, you know the answer to his question. Neither candidate addressed gun violence, despite the fact that the debate was held in Denver, not far from the sites of two the country's worst mass shootings: the 1999 Columbine High School shooting and this summer's mass-shooting at a movie theater in Aurora.   Mark Rosenberg, president and CEO of the Task Force for Global Health, has studied gun violence as a health issue, and is frustrated that research into how to prevent gun violence has slowed to a standstill. He takes a closer look at the issue as part of our "Don't Mention It" series on neglected campaign issues. "We're being held hostage to firearm violence," Rosenberg says, citing the  NRA  as the cause. "All of the science that could possibly give us answers is being stopped." While a tremendous amount of research has been done to stop other leading causes of death, like cancer, or traffic deaths, Rosenberg says that the NRA has successfully put a stop to any work that might have been done to decrease firearm injuries and deaths.   Rosenberg has done a lot of work on traffic deaths – "injuries that used to be considered accidents" – which he says are indeed preventable. Rosenberg thinks the same science could be applied to stop gun violence in America.   "We started looking at gun violence as a public health problem at the  CDC  in the late 80s and early 90s." Rosenberg says. "The standard line from the NRA is that you should have a gun in your house to protect you." The results of their study speak for themselves: not only does owning a gun not protect you, but it increases the risk of homicide for people in the home three times, and increases the risk of suicide five times. "I think that science is going to show that there are ways to restrict firearm injuries and deaths, and it means putting out some reasonable laws and reasonable policy in this arena." Rosenberg asserts that, out of fear of the findings, "[the NRA] just stopped the whole scientific endeavor."