Joaquin "El Chapo" Guzman (shown in 1993) heads the Sinaloa cartel, which is engaged in a bloody turf battle with La Linea, or the Juarez cartel. But an NPR investigation has found that the two cartels aren't competing on a level playing field: Federal forces appear to be favoring the Sinaloans, Mexico's largest, oldest and most powerful drug cartel. (AP)
