That raised a central question: whether the defendants could assert a "medical necessity defense," maintaining that they broke the law because their health required it.

The jury agreed, making this one of the rare times in American law in which the necessity defense was successfully used.

The case is an appeal by the Clinton administration of a federal court ruling in California that adopted the medical necessity defense.

However, the decision was later overturned on appeal, and the necessity defense was never brought before a jury.

A medical necessity defense is available for medical cannabis cases under a law passed in 2003.

Getting off the hook after the fact - mounting a successful "necessity defense," in lawyers' terms - isn't a perfect solution.

What role might a tenet of Massachusetts case law, the necessity defense, have played in the verdict?

The political necessity defense saw its demise in the case of United States v. Schoon.

While the committee "acknowledges the terrible dilemma that Israel confronts in dealing with terrorist threats to its security," it nevertheless rebuffed the country's necessity defense.

Twenty-six were tried on trespassing charges in November 1984, but were permitted to present a "necessity" defense, and all were acquitted.