I have served on both federal and county Grand Juries. Most of what you hear is pretty cut and dried.
The DA or Asst. DA describes the crime and then lists what evidence thay have against a suspect. The jury basically decides, Yes or No, There was a crime. And Yes or No, there is strong enough evidence to believe the suspect MIGHT have committed the crime.
Also a grand jury indictment does not need to be unanimus, A simple majority of a quorum is all that is needed to indict. I don't think most people know that.
We had several "no bills" on the jury I served.
No bills were passed here too.
13 out of 24 to indite.
Is there enough evidence to move to a trial. That was all we were allowed to discuss.