Mexican federal police escort Arturo Gallegos Castrellon after his 2010 arrest. The head of the brutal Barrio Aztecas gang, whose members are U.S. and Mexican citizens, is on trial in Texas for the killings of three U.S. consulate employees - two of whom were American citizens - in Ciudad Juarez, just over the border from El Paso. (Marco Ugarte/ASSOCIATED PRESS)