If anyone is like the judge and jury, it's the prosecutor. Most of the time judges just rubber stamp whatever the prosecutor wants to do, like a conveyor belt. And then the accused is not allowed to be there during the preliminary grand jury hearings (which is like a pre-trial) so the prosecutor pretty much has free reign over the jury's opinion and can sway them in any direction, sometimes being a little deceptive through selective omission of facts. I'll put it to you this way: A prosecutor has more control over what the jury thinks than the media did over public opinion about the George Zimmerman incident.
Not really how it works in my area. There is usually a prelim hearing with the defendant both lawyers judge and witnesses and then the judge certifies to the GJ. The prosecutor gives the Grand jury a summary and the charge he is pursuing, and introduces the witnesses to the grand jury and leaves. The grand jurors ask questions, there are no rules of evidence, and then decide if probable cause exists that a crime could have been committed on the facts they gather. The GJ are not the ones who are the trial jury.
