A more thorough explanation:

The Larrison rule is a legal doctrine in criminal law that allows a defendant to request a new trial based on newly discovered evidence of false testimony by a government witness. This rule is named after the case Larrison v. United States, which established the three requirements that must be met before a new trial can be granted:

1. The court must be reasonably well satisfied that the testimony given by a material witness was false.
2. Without the false testimony, the jury might have reached a different conclusion.
3. The party seeking the new trial was taken by surprise when the false testimony was given and was unable to meet it because they did not know of its falsity until after the trial.

For example, if a witness testified in a trial that the defendant was present at the scene of the crime, but later recanted their testimony and admitted that they were mistaken, the defendant may be entitled to a new trial under the Larrison rule if they can prove that the false testimony unfairly influenced the jury's decision.

The Larrison rule is intended to ensure that defendants receive a fair trial and are not convicted based on false or misleading testimony. It is an important protection for defendants in the criminal justice system.