I just read an interesting little story on The Conservative Voice. A little cheesy maybe, but instructive all the same. Take a minute to read it, it’s something everyone should know. Here is a little more info on it, lifted from Wikipedia
Jury nullification refers to a rendering of a verdict by a trial jury, disagreeing with the instructions by the judge concerning what is the law, or whether such law is applicable to the case, taking into account all of the evidence presented. Although a jury’s refusal relates only to the particular case before it, if a pattern of such verdicts develops, it can have the practical effect of disabling the enforcement of that position on what is the law or how it should be applied. Juries are reluctant to render a verdict contrary to law, but a conflict may emerge between what judges and the public from whom juries are drawn hold the law to be. A succession of such verdicts may signal an unwillingness by the public to accept the law given them and may render it a “dead-letter” or bring about its repeal. The jury system was established because it was felt that a panel of citizens, drawn at random from the community, and serving for too short a time to be corrupted, would be more likely to render a just verdict than officials who may be unduly influenced. Jury nullification is a reminder that the right to trial by one’s peers affords the public an opportunity to take a dissenting view about the justness of a statute or official practices.
In the 21st century, many discussions of jury nullification center around drug laws that some consider unjust either in principle or because they are seen to discriminate against African-Americans. A jury nullification advocacy group estimates that 3–4% of all jury trials involve nullification, and a recent rise in hung juries (from an average of 5% to nearly 20% in recent years) is considered additional evidence that juries have begun to consider the validity or fairness of the laws themselves.
The 1895 decision in Sparf v. U.S. held that a trial judge has no responsibility to inform the jury of the right to nullify laws. This decision, often cited, has led to a common practice by United States judges to penalize anyone who attempts to present legal argument to jurors and to declare a mistrial if such argument has been presented to them. Jurors are likely to be struck from the panel during voir dire if they reveal awareness of the concept of jury nullification.