What is a grand jury? What does it do?

I take it this question comes following the decision in Ferguson where a grand jury decided that the police officer who shot an unarmed boy should not go to trial for his murder.

Here's the low down on a grand jury.

A grand jury isn't grand like being a millionaire is grand, it's grand because it's bigger than regular juries,  grand in French means big, so a grand jury is just a big jury not a majestic one. conversely a petty jury is a small jury, not petty as in insignificant, petty as in the French word petit which means small.

A grand jury is a sort of preliminary hearing, so they hear evidence and make a decision as to whether a person should go to a full trial for a crime; not only that they can carry out investigations too.  So they can accuse and they can investigate by calling witnesses and demanding documents to be brought before them and so on.  They don't decide if someone is guilty, they decide if there is enough material to proceed to a trial.

Note that in Ferguson the grand jury did not say that the police officer was innocent, they said that there was not enough evidence to take him to court for murder.

It's important to note here that a grand jury does not sit in a court, nor are they answerable to a court.  It's essentially like a little mini trial before a trial that is presided by 16 to 23  random citizens.

Sound dangerous? Well, you're not alone in thinking that, right now only the United States of America uses grand juries as a preliminary hearing mechanism.  Even though they're used primarily in one country, their history is long, very long.  The first recorded grand jury was in the 12th century.  Here in Australia they were rarely used, but they remained able to be used until 2009.

So, to recap, a grand jury is a jury that decides whether there is enough evidence to send someone to face criminal charges.  It's called a grand jury not because it's regal or majestic but because it is bigger than most juries (between 16 and 23 people), and they are NOT part of a court, or sit within a court system they are out of it.

We don't have grand juries in Australia, but we do have preliminary proceedings, where a magistrate (it's usually a magistrate) will examine the evidence before her to deem whether there is enough evidence to bring an accused person to court for a full trail to determine their guilt or innocence. 

The magistrate doesn't determine guilt, she does what the grand jury would do, investigate as to whether the evidence exists to proceed.  The advantage of having a court officer do it in a court in Victoria is that there is judicial oversight, that is, judges oversee the process.  It happens in open court, under the rules of court and therefore, at least in theory, it's more transparent than asking 23 people to give an opinion, as educated as their opinion might be, they're not professional judges with legal training.