In the span of four years, El Salvador has gone from being the murder capital of the world to the safest country in the western hemisphere. The result: El Salvador has imprisoned 70,000 people it says are "associated with gangs" within two years. But with so many arrests, how can the country ensure that everyone they catch is a criminal? Nelufar Hedayat examines the impact of the controversial "State of Exception" in El Salvador and the U.S.