The American court system is not perfect. On occasion guilty people go free. And on occasion innocent people get hauled off to jail. Those occasions are probably less frequent than we think. All in all, the system works.
Being a convoluted and multi-tiered system, a person convicted of a crime gets numerous bites at the apple to win their freedom. If a prosecutor has any doubt or has a need to show fairness, he can go to the grand jury.
The people that serve on grand juries are volunteers. This relieves them of the pressure of job and family. They are free to take what time is needed to do the job. A presentation before a grand jury is not a trial. It is a hearing of the prosecutions evidence. They sit to judge that the prosecution has or has not a case to bring forward. If three quarters of them agree, they find a "true bill", and the case moves to trial.
In general, people who sit on juries take that responsibility very seriously. I was on a jury one time on a simple auto accident suit. When we went into the jury room, you would think we were deciding a life or death issue. I suspect that grand jurors carry an even heavier burden. I do not believe that old saw about a prosecutor being able to "indict a ham sandwich" is even close to true. People today are to skeptical.
I am particularly concerned with what is going on in Ferguson, Missouri. There have just been been too many loud mouths flapping in the breeze with a lot of attitude and little real information. From the President to the Attorney General to the New Black Panthers to Al Sharpton, they have lined up to create a modern day lynch mob. Their attitude: "the kid was black, the cop was white. It must be murder."
The blaze was already lit in that town. It did not need "news makers" supplying extra gasoline just to prove their relevance. I am betting, at this point, the grand jury comes back with no true bill against Officer Wilson.
I am also betting that if there is no true bill, our AG, who sees the world as racist, will convene a federal grand jury and most likely get an indictment because he will turn it into a civil rights issue. What is simply a local issue, which should be left local, will be turned into a federal issue for purely political reasons. This is the type of action that harms the honor of the court.