There was never any dispute about the basic facts of the case. On May 20, Marine Corporal Clemente Banuelos, 22, aimed his M-16 rifle at an 18-year-old goatherd named Esequiel Hernandez Jr. and shot him to death. Banuelos was part of a military surveillance unit helping control drug traffic in the tiny West Texas border town of Redford. He had apparently mistaken Hernandez--who was carrying a rifle and had fired it in the direction of the Marines--for one of the armed scouts who typically act as advance guards for drug smugglers.
A grand jury refused last week to indict Banuelos for...