Radio Live published some official documentation that reports information about 61 cases of mistrial that took place in 2009, 56 of them found at District Courts, while only 7 occurred at High Court.

However, New Zealand Justice Minister, Simon Power, had no justifications regarding the reasons behind the mistrials, their costs or how they would re-hold. He added that the Ministry does not normally keep a record of the information behind every case and the costs of mistrials. Still, Mr. Power resolved into investigating the main causes of mistrials, in order to lessen their number.

A judge declares a mistrial for different reasons; all aim on maintaining the integrity of the jurors. It can be because the jury cannot reach a verdict unilaterally, because one member of the jury is being prejudiced, or because the juror's ethnic or religious beliefs might compromise his decision, or even if a juror falls sick.

The Criminal Simplification Project, established in 2007 to reform the New Zealand's court system, debates the prospect of allowing the trial to continue even if two of the jurors were withdrawn for any reason. This way, the Ministry of Justice will end up decreasing the number of mistrials.