Ghost guns are firearms that can be made at home from kits or 3D printed parts. They’re unregulated and untraceable, meaning no background check is required to purchase them. Dr. Alex McCourt, a public health lawyer with the Hopkins Center for Gun Violence Prevention and Policy, talks with Stephanie Desmon about why these guns are so dangerous, what we know and don’t know about their use in violent crimes, and Biden’s proposal for ATF regulation.