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Jury nullification is a constitutional doctrine that allows juries to acquit defendants who are technically guilty, but who don’t deserve punishment. When a jury disregards the evidence and acquts an otherwise guilty defendant, it has practiced jury nullification. The jury is saying that the law is unfair, either generally or in this particular case.
Jury Nullification is perfectly legal and has a long history- indeed the framers of the Constitution intended jurors to serve as a check on bad prosecutions and ineffective laws. Northern jurors helped abolish slavery by refusing to convict people “guilty” of helping slaves escape. Nullification was also a factor in ending Prohibition, which locked up people for selling liquor, and created the same violent market and drive-by shootings (remember Al Capone?) that we now see for other illegal drugs.
The Fifth Amendment prohibits defendants from being tried for the same crime twice. This means that when a jury finds someone not guilty, there can never be a re-trial — even if the judge disagrees with the jury's verdict, or if there is compelling new evidence of guilt. The Supreme Court has ruled that this doctrine gives juries the power to nullify the law. If jurors believe the law is unjust, they don't have to apply it. There is nothing that anyone can do to prevent jurors from nullifying — under the Constitution, when it comes to acquittals, jurors have the last word.
Nullification works only in one direction — in favor of acquittals. If a jury finds someone guilty, and there is compelling evidence that the person is innocent, judges have the power to overturn the jury's conviction (that doesn't happen a lot in the real world). Giving jurors more power to acquit is based on the constitutional principle that it's better to let guilty people go free than to allow the innocent to be punished.
The idea that jurors should judge the law, as well as the facts, is a proud part of American history. The concept that jurors decide justice became an important part of American jurisprudence.
Perhaps the most shining example of nullification occurred during the shameful time in US history when slavery was legal. People who helped slaves escape committed a federal crime — violation of the Fugitive Slave Act. But when Northern jurors sat in judgment of these “criminals,” they would often acquit, even when the defendants admitted their guilt. Legal historians credit these cases with advancing the cause of abolition of slavery.
This strategic nullification is perfectly legal, and has two great benefits. First, it helps the community by safely reducing the number of incarcerated people. Second, it sends the message that “We the People” want fundamental change in our criminal justice system. This message is intended for both lawmakers and prosecutors.