6 Key Differences Between a Grand Jury and a Trial Jury

There are a lot of misconceptions and misunderstandings amongst average US citizens regarding the roles of the two main types of juries in the criminal justice system. Most people have a basic idea of how a trial jury—also known as a petit jury—normally works, with a group of the defendant’s peers being sworn to render an impartial verdict in the case after hearing the relevant evidence. However, the main confusion for most is with regard to grand juries.

The United States is the only common law country in the world that utilizes a grand jury system. Grand juries are used in criminal cases at the Federal level and in a majority of states, including Texas.

Many people mistakenly believe that grand juries serve essentially the same function as trial juries, and while these two are both comprised of average US citizens, they are in fact quite different.

Below we have detailed six of the biggest differences between grand juries and trial juries:


The role of a trial jury is to ascertain guilt beyond a reasonable doubt. Trial juries hear the evidence and determine whether the defendant is in fact guilty or not. They may also play a role in sentencing. Grand juries, on the other hand, only serve to advise the prosecutor on whether or not enough probable cause exists in the case to indict a suspect and bring them to trial on criminal charges. They do not determine guilt or innocence, rather they simply determine whether or not the evidence against the suspect is significant enough to warrant a trial and potential conviction. Additionally, the prosecutor is not required to adhere to the grand jury’s decision.


Grand juries differ significantly from trials in that the defendant and his or her attorney cannot attend the grand jury proceeding. Aside from support staff, the proceeding will only be attended by the jurors, the prosecutor, a judge, and any potential trial witnesses whom the prosecutor chooses to present to the jury.


Trial juries only hear very strict types of evidence that are allowable in court. Evidentiary requirements in criminal trials ensure that all evidence was legally obtained and fairly presented. Conversely, prosecutors may present any evidence they choose to a grand jury, including illegally obtained evidence.


Trial jury cases are a matter of public record and open to the public in most cases. Grand jury proceedings are kept private, though the suspect and his or her attorney may eventually obtain a transcript of the grand jury hearing.


Trial juries will generally meet nearly every day for a relatively short period of time. Grand juries will convene only a few times every month over a period of 6 months to over a year.


Usually, in order to obtain a conviction, a trial jury must be unanimous in its decision. All 12 jurors must agree that the defendant is guilty beyond a reasonable doubt. Grand juries can reach a decision to indict without unanimity. Generally, 16-23 jurors serve on a grand jury, and at the federal level only 12 must vote to indict in order to return an indictment to the prosecutor.

If you’ve been caught up in a criminal case and your case is going to a grand jury or could potentially be going to trial, it is vital that you enlist the services of a skilled defense attorney to guide you throughout both processes. Contact the Whalen Law Office today to learn how we can help.

Author Bio

James P. Whalen

James P. Whalen is the managing attorney and founder of Whalen Law Office, a Texas criminal defense firm offering personalized legal representation for various federal criminal charges. With a commitment to providing comfort and guidance during challenging times, Mr. Whalen serves as both an attorney and counselor to his clients, helping them navigate their cases while striving to restore normalcy to their lives.

In an inherently unbalanced criminal justice system, Mr. Whalen takes on cases with unwavering dedication. With decades of legal experience, he offers representation across various criminal charges, including white-collar crimes, violent crimes, drug charges, and more. Mr. Whalen’s numerous accolades, including Super Lawyer recognition and board certification in Criminal Appellate Law and Criminal Law, reflect his unwavering commitment to ethical and high-quality legal representation.

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