Homeland Security Secretary Kirstjen Nielsen testifies Tuesday in front of the Senate Judiciary Committee on a new DHS study, which found U.S. federal courts convicted at least 549 people with international terrorism-related charges between Sept. 11, 2001 and Dec. 31, 2016. Seventy-three percent of them were foreign-born, and 148 of those convicted had become naturalized U.S. citizens. Nielsen spoke to "CBS This Morning" co-host John Dickerson about the study.
