The grand jury issuing a report happened a few weeks ago (and for a different set of cases), the judge declaring a mistrial happened a few days ago. They’re separate things, but related because in both instances it’s the same set of police officers being caught screwing up in both cases.

Also, a few small details about grand juries in general (this can vary from district to district and state to state, but this is generally true),

It’s my understanding that a grand jury is convened prior to indictment myand consulted as a step to strengthen the prosecution of a case.

Not exactly. In theory, Grand Juries are actually supposed to be an additional restraint on prosecutors. Before prosecutors can publicly announce serious charges they’ve got to convince a grand jury to give them an indictment. That’s not as hard as getting a petit jury to hand out a guilty plea because a) the grand jury usually doesn’t need to be unanimous, b) the grand jury usually only listens to the prosecutor and doesn’t hear from the potential defendant’s attorney, but in theory at least requiring a Grand Jury’s approval is a way to keep prosecutors from indicting whoever they want just to jam them up to.

The grand jury chooses to indict

Not exactly. The grand jury hears the prosecutor’s evidence and arguments and then issues a report (like, search the term “grand jury report” and you’ll see a bunch of them from all over the place) that will say something like, “we authorize you to issue an indictment against Mr. Bill for violating state statute 101 like you asked for, we don’t authorize you to issue an indictment against Mr Bill for violating state statute 102 like you asked for, and we also authorize you to issue an indictment against Mr Bill for violating state statute 103 which you didn’t ask for but seems like it fits here. We will explain our reasons below.”

(Incidentally, it’s irrelevant here, but they only give the prosecutor permission to issue an indictment, issuing it and withdrawing it are all choices the prosecutor still gets to make (a lot of times a grand jury report authorizing an indictment is just what a prosecutor needs to show Mr Bill to get Mr Bill to testify against Mr Bob and Mr Bill gets to plead to something less than what the grand jury authorized in exchange for his cooperation)).

Since the jury is just made up of average people, who writes the report?

The average people do, albeit usually with a lot of assistance from court clerks when it comes to formatting and organizing evidence and things like that.

You might be asking yourself, “So how do these average people know the difference between state statute 101, 102, and 103 and what’s supposed to apply to which situation?” Mostly, that’s something the prosecutor explains to them (which is maybe part of the reason it’s been said that a good prosecutors could get a grand jury to let them indict a ham sandwich), but they are also supposed to use their own eyes and layperson common sense, so if a majority of them say something like, “the statute says ‘serious bodily harm,’ and we just don’t think the victim’s injuries were serious enough to be called that” then that prosecutor just doesn’t get the indictment they were asking for.

(I think there are also some jurisdictions where the grand jury can ask a judge questions, and in basically all of them the judge can jump in if the prosecutor starts just making stuff up, but generally the prosecutor gets to tell the GJ mostly whatever they want to).

e; Phrasing things with clarity so they can be understood is a task I struggle with on occasion and sometimes need multiple attempts to do halfway good because legal nonsense make brain hurt