Former Massey Energy Company Chairman and CEO Don Blankenship, seen in July 2010, has pleaded not guilty to conspiracy charges associated with the 2010 West Virginia mine explosion that killed 29 men. Jacquelyn Martin/AP hide caption

itoggle caption Jacquelyn Martin/AP

Oklahoma City Bombing: The Albert P. Murrah Federal Building shows the devastation caused by a fuel and fertilizer truck bomb on April 19, 1995. The blast killed 168 people and injured more than 500. Bob Daemmrich/AFP/Getty Images hide caption

itoggle caption Bob Daemmrich/AFP/Getty Images