mistrial | Definition

Doc's CJ Glossary by Adam J. McKee
Course: Introduction

A mistrial is an invalid trial caused by fundamental error.

Imagine a game that suddenly stops because of an unfair rule or unexpected event. It’s frustrating, right? This situation is comparable to a mistrial in the legal world. A mistrial happens when something fundamentally unfair or wrong occurs during a trial, making it impossible to proceed with justice.

The Causes of a Mistrial

These don’t just happen out of the blue. Certain circumstances or events trigger them. Here are some common causes:

Jury Misconduct

Juries have a crucial role in a trial, deciding if the defendant is guilty or not guilty. They must follow strict rules to ensure their verdict is fair. But what if they don’t? What if a juror researches the case outside the courtroom or discusses the case with outsiders? These actions can cause a mistrial because they risk biasing the juror’s decision.

Unfair Prejudice

If something happens during a trial that unfairly prejudices the jury against the defendant, a mistrial might be declared. For example, suppose a lawyer makes inappropriate comments about the defendant’s character. In that case, it might unduly influence the jury.

Hung Jury

In some cases, the jury can’t reach a unanimous decision, known as a hung jury. They’ve tried their best, but they’re stuck. The judge might declare a mistrial because of this deadlock.

Serious Procedural Error

Sometimes, errors happen during the trial process. Maybe crucial evidence was wrongly admitted or denied, or perhaps the judge made a mistake in explaining the law to the jury. If these errors might change the trial’s outcome, the judge could declare a mistrial.

Health Issues or Emergencies

Life is unpredictable. An emergency could happen at any time, affecting the trial participants. For instance, if a juror, the judge, or a lawyer has a serious health crisis during the trial, it might cause this to happen.

After a Mistrial is Declared

So, what happens when a judge declares a mistrial? It’s like hitting the reset button on a game. The trial needs to start all over again, beginning with the selection of a new jury. However, it’s important to know that a mistrial doesn’t mean the defendant is free to go. It just means the justice system must try again to reach a fair verdict.

The Importance of Mistrials

Mistrials might sound like an annoyance, a do-over no one wanted. But they’re crucial for fairness in the justice system. They ensure that every defendant gets a fair shot, that every trial follows the rules. Without the option of declaring a mistrial, an unfair trial could lead to an unjust verdict.


A mistrial is a trial rendered invalid due to a significant error. It safeguards the fairness of the legal process. It guarantees that if things go wrong, the justice system can hit restart and try again. Thus, despite the frustration it might cause, a mistrial is a vital part of maintaining justice and fairness.

[ Glossary ]

Last Modified: 06/04/2023

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