The U.S. man accused of killing 12 people at a movie theater in Colorado faces a preliminary hearing this week. But what exactly is a “preliminary hearing”?

In U.S. criminal cases, a preliminary hearing is a court proceeding used to determine whether a person charged with a felony should stand trial.

Prosecutors present their case against the defendant to a judge, who decides whether there is sufficient evidence to put the suspect on trial.

To prevent exposing its trial strategy, the prosecution typically presents only enough evidence and testimony to show the probability of guilt, known in legal terms as “probable cause.” And, the defense often shares no evidence, focusing instead on cross-examining the government's witnesses and raising questions about other evidence presented against the defendant.

If there is not convincing evidence to send the case to trial, the judge will dismiss the charges.

Some U.S. states use a grand jury indictment process instead of a preliminary hearing. A grand jury is a selected group of citizens that decides, based on the prosecution's evidence, whether a case should go to trial.