Grand juries have received a great deal of attention lately, causing me to ask: What, exactly, are grand juries? And what do they do? And how do they do it?

Since I’ve never practiced criminal law, this is new territory for me. But here is some of what I’ve learned.

To begin, grand juries consist of a panel of citizens chosen in an impartial process and given certain powers. Grand jurors come from the same pool of individuals as trial jurors.

In the federal system, grand juries have between 16 and 23 members. In Colorado, grand juries usually have 12 members, but a court can expand this to 23.

In Colorado, grand jurors normally serve a term lasting up to 12 months. However, this can be extended, not to exceed 18 months. In the federal system, grand jurors serve until they are discharged. But, they cannot serve longer than 18 months unless the court appointing the jury extends the term. Extensions normally do not exceed six months. Grand juries don’t meet every day.

What grand juries do is to investigate suspected criminal activity. Prosecutors present to the jurors testimony and documents they believe show “probable cause” that a crime has been committed. Suspects don’t participate in grand jury proceedings, making the proceedings something of a one-sided trial.

The proceedings are conducted under strict rules of secrecy. After the grand jurors complete their investigative activities, they decide whether or not the information they have received justifies proceeding with a prosecution. They don’t, however, finally decide a case — trial jurors do that — and the “probable cause” standard for sufficient-to-proceed is much lower than the “beyond a reasonable doubt” standard necessary for a conviction.

At the end of their investigation, the grand jurors decide whether or not to bring charges against a suspect in the form of an “indictment.” If a decision is made to indict, it’s called a “true bill.” If the grand jurors conclude an indictment will not be issued, their decision is called a “no true bill.” ( Who says the law isn’t logical?)

If the decision is “no true bill,” the record of the proceedings will remain sealed. If a grand jury does issue an indictment, it will remain sealed until there is an arraignment. This is when a suspect is brought before a judge and is told what charges the prosecutor will pursue and what rights the suspect (now a defendant) has.

In the federal criminal justice system, suspects accused of a federal offense that rises to the level of a felony have a right to a grand jury, under Article V of the U.S. Constitution. So, a grand jury indictment is necessary for a case to proceed to trial.

State criminal justice systems have various ways criminal cases are commenced and suspects are given protection against questionable prosecutions. In New York, for example, someone being accused of a felony under that state’s laws has the right to a grand jury proceeding. Not so in Colorado, where a suspect’s protection against a prosecution lacking probable cause usually comes in the form of a “preliminary hearing” conducted by a judge.

Nonetheless, prosecutors sometimes request grand juries as a way to expand a criminal investigation. That’s in part because grand juries can subpoena witnesses and demand documents, and hearsay testimony is allowed. In Colorado, grand juries can be convened and given jurisdiction over crimes occurring in a single county, a judicial district consisting of several counties, or statewide.

Other grand jury trivia I came across includes that the basic idea of a grand jury dates back to England in the Middle Ages and, in 1215, found its way into the Magna Carta. And, the “grand” in the name comes from the French word “grand,” meaning big. (Trial juries, which tend to have fewer jurors, are called “petit” juries.) And, in Colorado, people convicted of a felony are not allowed to serve on a grand jury. They can, however, serve on a trial jury.