Going waaaay back in time today, people. Deal with it. Found in Barbara Holland's Gentleman's Blood, page 11.
“In France, a splendid duel was fought in 1400 between a suspected murderer and his accuser, a dog. The Chevalier Maquer killed Aubrey de Montdidier in the Forest of Bondy, near Paris, and buried the body. The only witness was Montdidier’s greyhound. The dog went back to town to a friend of his master’s and led the friend to the spot, where he whined and scratched the ground. The body was recovered and reburied, and the greyhound moved in with the friend. Shortly thereafter, it met up with Maquer and attacked him viciously; three men had to pull it off him. The dog was an otherwise gentle and amiable sort, but it kept on flying at Maquer whenever it saw him.
"This was reported to the king, who decided it was definitely an accusation and arranged for the single-combat trial. The fight took place on the Ile de France in Paris, Maquer with a lance, the greyhound with its natural weapons. The dog sprang on the man with amazing ferocity and clamped its teeth around his throat and couldn’t be shaken off. Maquer screamed that he’d confess if they’d pull off the dog.
"This, in contemporary eyes, proved the justice of combat trials pretty conclusively, and Maquer was hanged and strangled on the gibbet at Montfaucon” .
I just imagine the king being like, "Guys, I know that dog. That is a totally lucid dog. Let's do this."
I want to make a joke about the film The Advocate, set in 15th-century France, where a donkey is on trial for fornication and a pig is on trial for murder, but I can't because (according to my friend who is doing her PhD in medieval history) that is a straight-up, literal report of things that happened all the time, since animals in France were subject to the same laws as humans.