"Two court cases likely had some bearing in the grand jury’s decision-making process:
1. In Jones v. City of St. Louis, 92 friend.Supp.2d 949 (E.D. Mo., 2000) the federal district court, in a lawsuit from the police use of deadly force, held that the use of deadly force is reasonable where the officer has probable cause to believe the suspect poses a threat of serious physical harm, either to the officer or others.
2. In Fitzgerald v. Patrick, 927 friend.2d 1037 (8th Cir., 1991) the 8th circuit federal court of appeals, in another police use-of-force case out of Missouri, said law enforcement officers are justified in using deadly force in self-defense or in defense of a third person if a reasonable person in similar circumstance would believe it was necessary."
http://www.policeone.com/ferguson/articles/7782643-Why-Officer-Darren-Wilson-wasnt-indicted/
One thing that needs to be pointed out;
This wasn't some sort of "special" grand jury, that was assembled to just hear this case.
They had been picked by the judge.... months before the event
even happened.
Grand juries serve for a period of time, and hear what ever cases are presented to them.