People hold signs during a demonstration in Washington on March 24, 2012 to demand justice for Trayvon Martin, an unarmed black Florida teenager shot to death by a white volunteer guard on February 26. The suspect in the shooting, George Zimmerman, told police he shot Martin in self-defense while working as a neighborhood watch captain. Critics say 17-year-old Trayvon Martin was shot in the chest for being young and black in a gated community where he was not wanted, rather than because he did anything wrong. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)