ST. LOUIS — A grand jury heard evidence for months as it weighed whether to indict Ferguson police Officer Darren Wilson in the Aug. 9 fatal shooting of Michael Brown, which was followed by sometimes violent protests. Some answers to common questions about the grand jury:

Q: What was the grand jury deciding?

A: The grand jury considered whether there was enough evidence to charge Wilson with a crime and, if so, what that charge should be.

Q: How was the grand jury different from trial juries?

A: A grand jury can determine only whether probable cause exists to indict, not whether a person is guilty. If a jury indicts someone, a separate trial jury is seated to decide whether to convict or acquit.

Q: How many people were on the grand jury and how were they selected?

A: The grand jury was composed of 12 people “selected at random from a fair cross-section of the citizens,” according to Missouri law. The jurors, whose identities were kept secret, were 75 percent white: six white men, three white women, two black women and one black man. St. Louis County overall is 70 percent white, but about two-thirds of Ferguson’s residents are black. Brown was black. The officer is white.

Q: Was the grand jury appointed for this specific case?

A: No. It was appointed for a four-month term. The grand jury was hearing routine cases around the time Brown was killed and then turned its attention to the shooting.

The jury’s term was due to expire Sept. 10. That day, county Judge Carolyn Whittington extended the term to Jan. 7 – the longest extension allowable by state law. The investigation was always expected to go longer than the typical grand jury term.

Q: How often did the grand jurors meet?

A: Their normal schedule was to meet once a week.

Q: Who was in the grand jury room?

A: The grand jury, a prosecutor and a witness. Grand jury proceedings are closed to the public.

Q: What happened when the grand jury convened?

A: Prosecutors presented evidence and summoned witnesses to testify. Witnesses must testify unless they invoke the Fifth Amendment of the U.S. Constitution, which protects against self-incrimination.

Typically, grand jurors hear a condensed version of the evidence that might be presented at a trial. In the Ferguson case, grand jurors received more extensive evidence and testimony.

Q: Who testified to the grand jury?

A: The only witnesses known to have testified were Wilson and Dr. Michael Baden, who did a private autopsy on Brown on behalf of his family. Other witnesses and experts may also have appeared.

Q: What charges could be filed?

A: At the lower end is second-degree involuntary manslaughter, which is defined as acting with criminal negligence to cause a death. It is punishable by up to four years in prison.

First-degree involuntary manslaughter, defined as recklessly causing a death, is punishable by up to seven years in prison. Voluntary manslaughter, defined as causing a death “under the influence of sudden passion arising from adequate cause,” is punishable by five to 15 years in prison. Second-degree murder is defined as knowingly causing a death, or acting with the purpose of causing serious physical injury that ends up resulting in death. It is punishable by life in prison or a range of 10 to 30 years.

The most serious charge, first-degree murder, can be used only when someone knowingly causes a death after deliberation and is punishable by either life in prison or lethal injection.

Q: Do charges require a unanimous vote?

A: No. Consent from nine jurors is enough to file a charge in Missouri. The jury could also choose not to file any charges.

Q: Can jurors speak to the public?

A: No. Disclosing evidence, the name of a witness or an indictment can lead to a misdemeanor charge.