The U.S. Constitution's definition of treason was the most restrictive of its time. Its "two witnesses" provision was unprecedented, and is unique in American law.

The drafters -- themselves just 12 years away from having committed treason against the English king -- were wary of its use in Britain, France and elsewhere as a weapon to silence political opponents.

As a consequence, it has rarely been prosecuted on these shores. Benedict Arnold, the American whose name is synonymous with treason, fled to England in 1779 before he could face charges for treason and died peacefully there.

Here is the reference to treason in the Constitution and a selection of prosecutions.

Article III, Section 3:

Treason against the United States, shall consist only in levying war against them, or in adhering to their enemies, giving them aid and comfort. No person shall be convicted of treason unless on the testimony of two witnesses to the same overt act, or on confession in open court.

The Congress shall have power to declare the punishment of treason, but no attainder of treason shall work corruption of blood, or forfeiture except during the life of the person attainted.

("Attainder of treason" referred to a practice in Europe at the time of impoverishing, ostracizing and banishing a traitor's family and descendants.)

Aaron Burr — third vice president of the United States, 1801-05, planned a Mexican "empire," 1807.

Sidelined politically and embittered after he killed archrival Alexander Hamilton in a duel in 1804, Burr conspired with Gen. James Wilkinson to invade Mexico and establish an empire.

Wilkinson turned him in, and Burr was tried for treason in 1807, based on an accusation that his empire was to include parts of the western United States. Chief Justice John Marshall, who acquitted Burr, said that to prove treason, "war must actually be levied against the United States ... conspiracy (to levy war) is not treason."

Thomas W. Dorr — Rhode Island rebel, 1841-42.

Dorr is the only man to be convicted of treason against a state, Rhode Island. He led an uprising against Gov. Samuel King because the state was still adhering to its pre-Revolutionary constitution, and had not enfranchised non-property owners or established a bill of rights. His supporters elected him governor in 1842 in an extralegal convention, and for a while Rhode Island had two administrations. King had him tried and sentenced to life imprisonment for treason in 1844. The same year, the U.S. Supreme Court upheld the conviction against claims that one could not commit treason against a state. Dorr was pardoned in 1845, and his reforms were soon adopted.

Max Haupt — Father of a saboteur, 1942.

Haupt was the father of Herbert Haupt, one of eight Nazi saboteurs convicted by a military tribunal in 1942, and one of six executed. The elder Haupt was charged in 1943 with treason for "giving aid and comfort" to the enemy because he had harbored his son in his Chicago apartment, bought him a car and found him a job, knowing that he planned sabotage.

Max Haupt didn't dispute the facts -- it was he who had volunteered the information to the FBI in a fruitless attempt to show that his son was manipulated by others. Instead, the father argued that he had committed the "commonplace, insignificant and colorless" acts of a father. A jury convicted Haupt in 1944, but recommended mercy; he was spared death, and was sentenced to life.

Upholding the conviction in 1947, Supreme Court Judge Robert Jackson said: "It is argued that Haupt merely had the misfortune to sire a traitor ... the jury apparently concluded that the son had the misfortune of being a chip off the old block."

Tomoya Kawakita, the tormentor who came home, World War II.

Kawakita, born in California, went to Japan in 1939 when he was 18 to visit his grandfather. He stayed, never renouncing his U.S. citizenship. He was employed as an interpreter with a Japanese nickel company. He was never conscripted, but Japanese authorities used him as an interpreter in a prisoner of war camp.

He readily joined in the abuse of American prisoners, "going beyond any conceivable duty of an interpreter," according to the U.S. Supreme Court. He beat some, pushed another into a cesspool and forced the obviously ill into hard labor.

After the war, he re-registered as a U.S. citizen and returned home. His former victims, who knew him as "Meatball," spotted him and turned him in, and he was sentenced to death for treason in 1952. President Eisenhower commuted his sentence to life in 1953.