Yes it is.
But my understanding is that in most states a prosecutor has no legal obligation to submit a balanced review of the evidence to the grand jury. He's prohibited from presenting evidence he knows or reasonably suspects is false.
But unlike during the trial, he is not obligated to present excuplatory evidence.
No, I'm not really comfortable with this, but then the grand jury hearing isn't intended to be a "pre-trial," which is what the Wilson hearing turned into.
BTW, the prosecutor could also have legally not presented any evidence to the jury that would fit the "narrative." But instead apparently he gave it all to them.
If a prosecutor in a grand jury knows there are 20 witnesses that support Wilson's story and there are 4 witnesses that contradict Wilson's story, then it is his obligation to present all those witnesses.
Now if Wilson's side of the story is poorly supported by some of the witnesses, then it's not his obligation to call those witnesses.
I believe you are misinformed.
The prosecutor is NOT obligated to present ANY exculpatory evidence to the jury at trial. He IS obligated to give any exculpatory evidence he possesses to the defense IF they request it, which the defense routinely does. It is then up to the defense to decide which exculpatory evidence, if any, to present to the jury.
All too frequently, the prosecutor will do whatever back-flips he can to hide exculpatory information from the defense (see Mike Nifong). If he gets caught at this, it can be grounds for having the verdict overturned, and in some cases the prosecutor has been held in contempt, although the latter rarely happens.