What is a mistrial, and How Does it Affect a Criminal Case?

A mistrial is a trial or criminal case that ends before the court makes a verdict.

Therefore, such a trial has no legal effect on the accused. For example, an accused person cannot serve a sentence.

However, reconstitution of a new jury or judge may lead to retrial of the case.

In this article, we will explain what a mistrial is in a criminal case, the factors that can result in a mistrial, what happens after a mistrial, and how it differs from other outcomes.

What is a Mistrial in a Criminal Case?

What is a mistrial, and How Does it Affect a Criminal Case
How a judge will normally rule in a mistrial case, Image by Canva

A mistrial in a criminal case is a trial that ends without either a conviction or an acquittal of the defendant.

Thus, in such a case, neither has the jury found the defendant guilty nor innocent of the charges answerable.

However, a mistrial does not vindicate the defendant; rather, it indicates that the case has no resolution.

A mistrial can be declared by the judge overseeing the trial.

In addition, either the prosecution or the defense may motion the court to declare a mistrial.

Depending on the circumstances and the severity of the factor(s) causing the mistrial, a judge has the choice to grant or deny the motion.

One of the considerations judges determine is if this factor leading to mistrial will not happen by giving new instructions to the jury.

If the instructions do not work the judge will then determine if the factor prejudices the trial.

Several Factors that Can Result in a Mistrial

The factors are listed below:

Lack of jurisdiction

Jurisdiction is the threshold for a court to hear and determine a matter.

For example, Federal courts of the United States have limited jurisdiction, meaning they can only hear cases authorized by the United States Constitution or federal statutes.

In the case of a mistrial, it means that a court did not have the legal authority to hear the case or try the defendant.

Jury selection error

This scenario happens when a jury is not properly constituted or qualified, or there is evidence of bias or discrimination among members of the jury.

Inadmissible evidence

A mistrial occurs when a judge determines that a piece of evidence obtained, admitted and presented to the jury is irrelevant, unreliable or illegally obtained.

Improper comments

Comments that are unfair, inflammatory, or misleading made by the judge, the attorneys, the witnesses, or the media within the hearing of the jury can lead to bias.

Hung jury

A mistrial will happen when the jury cannot reach a unanimous verdict after reasonable deliberation.

Death or illness

The death or serious illness of the judge, an attorney, a juror, or a key witness prevents the continuation of the trial.


Misconduct by an attorney, a juror, a witness, or a party to a trial tends to affect the fairness or integrity of the trial.

What is a Mistrial Hung Jury?

A mistrial hung jury occurs when the jury, after reasonable deliberation, fails to agree on a unanimous decision.

A hung jury will often indicate the possibility of reasonable doubt among some or all of the jury about whether a defendant is innocent or guilty.

A hung jury can happen for various reasons, such as:

  • Conflicting or insufficient evidence produced in court.
  • Differing interpretations or applications of the law among the jury.
  • Divergent personal beliefs or values among the jury.
  • External influences or pressures among the jury.

When a hung jury occurs, the judge may ask the jury to continue deliberating.

A photo of Members of a jury. Photo courtesy: Copyright 2009, Mike Watson Images Limited.

In some instances, the judge gives the jury additional instructions or guidance.

However, if the jury remains undecided, the judge will declare a mistrial and discharge the jury.

The case may then have a retrial or end through dismissal depending on the factors discussed above.

What Happens if There Is a Mistrial?

A mistrial may lead to several outcomes:

  • A prosecutor may dismiss the charges, offer the defendant a plea bargain, or retry the case with a new jury or judge.
  • A defendant may accept a plea deal, request a dismissal, or prepare for another trial.
  • A judge may order a new trial on all or some of the charges, or dismiss some or all of the charges.

The decision by the courts to retry or dismiss a criminal trial depends on several factors, such as:

  • The strength of the evidence and the likelihood of conviction.
  • The availability and willingness of witnesses and evidence.
  • The severity and nature of the charges and the potential sentence.
  • The cost and resources involved in another trial.
  • The public’s interest and safety.
  • The wishes and rights of the defendant and the victim.

What is Mistrial Without Prejudice?

A mistrial without prejudice means that another trial may be initiated by the prosecutor based on the same charges.

In such a case, a defendant is not protected by the principle of double jeopardy.

Double Jeopardy refers to a constitutional right to not be tried twice for the same offense.

A mistrial without prejudice allows the prosecutor to retry the case if they choose to do so and does not imply any judgment on the merits of the case.

A retrial usually occurs when there is no fault or bad faith by either party.

Furthermore, retrial can happen when there is a hung jury, a serious error in procedure, or an unforeseen event.


A mistrial occurs when a jury is unable to reach a verdict and there must be a new trial with a new jury.

In a criminal case, a mistrial does not mean that a defendant is guilty or innocent.

A mistrial can be retried or dismissed, depending on several factors.