Jury nullification
Jury nullification occurs in a trial
A trial is, in the most general sense, a test, usually a test to see whether something does or does not meet a given standard.It may refer to:*Trial , the presentation of information in a formal setting, usually a court...

 when a jury
A jury is a sworn body of people convened to render an impartial verdict officially submitted to them by a court, or to set a penalty or judgment. Modern juries tend to be found in courts to ascertain the guilt, or lack thereof, in a crime. In Anglophone jurisdictions, the verdict may be guilty,...

 reaches a verdict
In law, a verdict is the formal finding of fact made by a jury on matters or questions submitted to the jury by a judge. The term, from the Latin veredictum, literally means "to say the truth" and is derived from Middle English verdit, from Anglo-Norman: a compound of ver and dit In law, a verdict...

 contrary to the judge's instructions as to the law.

A jury verdict contrary to the letter of the law pertains only to the particular case before it; however, if a pattern of acquittals develops in response to repeated attempts to prosecute a statutory offence, it can have the de facto effect of invalidating the statute.