What is the idea behind Grand Juries?

I understand that a Grand Jury is meant to see if the state has enough evidence to merit taking a person to trial for a given crime. As I understand it this is a requirement for federal crimes but may or may not be required at the state level (up to the individual state).

My question is what is the point of these things? I have a vague recollection that Grand Juries pass well over 90% of the cases they review to the courts for trial. As such I have heard accusations that they amount to little more than rubber stamps for the prosecution. Given that they just want to find if there seems to be enough evidence to merit a trial the burden of proof is very loose.

Of course, one would hope the state wouldn’t bother prosecuting a case that they didn’t feel they had a good chance of winning so the 90+% rate may not be alarming but given that why have this seemingly extra step in the judicial process?

In law school we used to say that any prosecutor worth his salt could get a grand jury to indict a ham sandwich. There’s no judge in the grand jury room, and the accused has no opportunity to be present, be heard, or to have the presence of counsel, so the deck is definitely stacked against him.

You’re right that the grand jury doesn’t seem like that big a deal these days, and indeed I’d tend to agree – most of the time. However, it’s very important when there’s a real possibility of corruption in the D.A.'s office, which is fortunately not a huge problem. It used to be, though, and while out-and-out graft is pretty rare these days, politicking is still a big issue and can occasionally lead to a politically-minded prosecutor taking a case to trial which shouldn’t go. I can also see how a grand jury in certain cases could prevent racial scapegoating – although that’s a two-edged sword.

There are advantages for the prosecutor as well. The grand jury has the power to issue subpoenas, which means it can compel people to testify and to produce documents or other tangible things. (It can’t compel the testimony of the accused, since he has a 5th Amendment right to refuse to testify against himself.) Without a grand jury, a D.A. & the cops can investigate and can get search warrants upon probable cause, but they cannot force recalcitrant witnesses to talk to them. A grand jury can.