Spoiler Alert: This post contains spoilers for the Game of Thrones episode "Laws of Gods and Men"
Updated with additional information, May 15, 2014
The latest twist in the ongoing Game of Thrones trial drama was one nobody in King's Landing saw coming: though Tyrion Lannister was essentially offered a plea deal in his trial for the murder of his nephew King Joffrey, he refused the chance for mercy. Instead, he invoked his right to trial by combat. It is, as James Poniewozik points out in his recap of the episode, a strategy that's worked for him before.
In Westeros, when someone is accused of a crime, he always has the right to demand such a trial in place of a judge and jury. The accused and the accuser (or the state, such as it may be) may each choose a champion to fight on their behalves.
It may seem like an extreme move but trial by combat is actually a real thing, as are many of the practices in the Thrones universe. As Business Insider pointed out back when Tyrion first used that legal loophole, some people actually think that those accused of crimes in the U.S. — like, today, not back in colonial times — have the right to demand such a decision-making process. The idea is that when the original colonies were founded they used British common law, but England didn't repeal the right to trial by combat until 1819; in theory, because trial by combat was O.K. in the U.K. in 1776, the U.S. picked up that tradition, and the framers of the Constitution didn't make an effort to lay out anything to the contrary. In practice, however, it's never been attempted and would be unlikely to get any court's approval. (A guy in the U.K. tried, hilariously, about a decade ago. It didn't work.)
But trial by combat isn't just a matter of might-makes-right: in theory, the gods will favor the innocent. The winner is not meant to be the strongest one or the luckiest one but the one meant to be saved.
It's a concept that holds true for lots of other strange-but-true trial options from history. Most of them fall under the category of "trial by ordeal," which means that if the accused made it through something that's usually painful (or fatal) that was an indicator of innocence. There was the ordeal of boiling water, a medieval method in which the accused had to stick his hand in boiling water—if he got scalded, he was guilty— and the similar, and metaphor-inspiring, trial by fire. There was dunking, the method of testing witches by seeing whether they float, which is even more common in pop culture than trial by combat. There was the ordeal of the bier, used to assess guilt in murder trial by seeing whether the corpse would begin to bleed again when touched by the accused; if yes, that meant guilt. In one example of ordeal by divination, having a candle that burned longer than someone else's meant you were in the right. There was even such a thing as trial by bean: the accused ate the poisonous Calabar bean, and if he threw it up and thus survived, he was innocent.
As great as it is that trial by jury is a thing, trial-by-something-else does have its defenders: as the economist Peter Leeson has pointed out, there's reason to believe that ordeals did sometimes indicate guilt correctly. The thought is that an individual who knows he's guilty will approach the trial differently than someone who knows he's innocent; if everyone really believes that the gods are choosing the outcome, willingness to participate is already an indicator of innocence.
If it worked in history, it just might work for Tyrion Lannister too.
UPDATE: An intrepid reader points us to an example of at least one near-attempt to use trial by combat in U.S. court, a 1983 case in Delaware. As the judge pointed out at the time, at least one reason it wouldn't work is that dueling is against the law.