A petit juror's responsibility is to determine issues of fact in civil and criminal cases and to reach a verdict based on those findings. A grand juror's responsibility is to determine probable cause in criminal cases based on the facts and accusations presented by the prosecutor; if the grand jury finds probable cause, an indictment will be handed down. An indictment is the most common way a criminal case begins. In summary, grand jurors decide whether there is enough evidence to indict, while petit jurors decide guilt or innocence.