On Friday, in a federal courtroom in Tucson, Ariz., an agent of the U.S. Border Patrol for the first time will be arraigned on charges of murder for shooting and killing a Mexican national across the international border.

On Oct. 10, 2012, Agent Lonnie Ray Swartz, standing behind the border fence in Nogales, Ariz., shot 16-year-old Jose Antonio Elena Rodriguez, who was walking along a sidewalk in Nogales, Sonora. The agent claims he acted in self-defense against rock-throwers on the other side....

Standing on International Street in Nogales, Mexico, in the exact spot where the teenager was shot to death, it's a wonder how Swartz could have felt threatened by rock-throwers.

The border fence across the street from where the teenager was shot is built on top of a steep embankment, high above the street where the Mexican rock-throwers allegedly were.