There are instances wherein a court trial cannot continue due to an error or an event that corrupts the whole process leading to the impossibility of an impartial resolution. When such an event occurs, the court hearing is declared a mistrial.
There are several valid reasons as to why a judge may declare a mistrial. Such reasons may include the lack of jurisdiction a court may have over the case, improper admittance of evidence or testimonies, misconduct of any individual that prevents due process, a hung jury, or disqualification of a juror after the jury has been impaneled. A hung jury means that the jury cannot decide unanimously on a verdict while the disqualification of a juror only leads to mistrial if no suitable alternate juror can be found or if the litigants cannot agree to continue. When a mistrial is called, a retrial is in order for the same issue, but all other matters instigating the mistrial must be resolved.
A mistrial may also be requested if litigants or legal counsels of the litigants find that unfair statements or comments have been made or crucial evidence or testimonies are not admitted. This is done by filing a motion for mistrial with the court of law, and subject to the approval of the judge. Once a judge has declared a mistrial, the judge may also declare the case to be with or without prejudice. In the event that it is declared with prejudice, the case can no longer be retried.