Final answer:
Grand juries determine if there is enough evidence for a trial, issuing an indictment, while trial juries decide guilt or innocence based on evidence presented during the criminal trial. Grand juries do not determine penalties or engage in civil trial decisions.
Step-by-step explanation:
The main function of a grand jury is to decide whether there is enough evidence to bring a person to trial, formally known as issuing an indictment. This is particularly necessary in federal felony cases as per the Fifth Amendment. Grand juries don't determine guilt or innocence; that decision is the sole responsibility of a petit jury (or trial jury) during the criminal trial. It's a trial where the defense and prosecution present their cases before the judge and petit jury, with the latter weighing the evidence to decide guilt or innocence based on 'beyond a reasonable doubt'. Unlike grand juries, trial juries do sometimes decide on penalties, such as in death penalty cases. The appeal process follows convictions or acquittals, potentially going to specialized appellate courts or the state supreme court.
Furthermore, the role of a grand jury has been designed to protect against unfounded criminal prosecutions. Grand juries involve citizens reviewing the evidence presented by the prosecution to determine if a person should face trial. This jury remains distinct from the petit jury, which will later be seated for a criminal trial to hear the case in its entirety and ultimately render a verdict of guilty or not guilty. However, trials also encompass aspects like plea bargaining before entering the trial phase, whereas grand juries come into play before these considerations.
In civil cases, the role of a jury can differ significantly from their role in criminal cases. The standard of proof is lower--'preponderance of the evidence' as opposed to 'beyond a reasonable doubt'. But it's important to understand that grand juries are not involved in civil trials. Their function remains within the scope of criminal proceedings and only for indictments. They do not engage in the ultimate question of guilt, nor do they render decisions in civil matters.