§ 391. 3. Trial by battle.-The trial by battle, duel or single man, combat, which was another species of presumptuous appeals to Providence, under an expectation that Heaven would unquestionably give the victory to the innocent or injured party.  The nature of this trial in cases of civil injury, upon, issue joined in a writ of nor a right, was fully discussed in the preceding book, to which I have only to add, that the trial by battle may be demanded at the election of the appellee, in either an appeal or an approvement; and that it is carried on with equal solemnity as that on a writ of right: but with this difference, that there each party might hire a champion, but here they must fight in their proper persons. And therefore, if the appellant or approver be a woman, a priest., an infant or of the age of sixty, or lame or blind, he or she may counterplead and refuse the wager of battle, and compel the appellee to put himself upon the country.  Also peers of the realm, bringing an appeal, shall not be challenged to wage battle, on account of the dignity of their persons, nor the citizens of London, by special charter, because fighting seems foreign to their education and employment.  So, likewise, if the crime be notorious; as if the thief be taken with the mainour, or the murderer in the room with a bloody knife, the appellant may refuse the tender of battle from the appellee; for it is unreasonable that an innocent man should stake his life against one who is already half convicted.

§ 392.   Procedure in trial by battle.-The form and manner of waging battle upon appeals are much the same as upon a writ of right; only the oaths of the two combatants are vastly more striking and solemn.  The appellee, when appealed of felony, pleads not guilty, and throws down his glove, and declares he will defend the same by his body: the appellant takes up the glove, and replies that he is ready to make good the appeal, body for body.  And thereupon the appellee, taking the Book in his right hand, and in his left the right hand of his antagonist, swears to this effect.  "Hoc audi, homo, quem per manum teneo," etc.,  "Hear this, 0 man, whom I hold by the hand, who callest thyself John by the name of baptism, that I, who call myself Thomas by the name of baptism, did not feloniously murder thy father, William by name, nor am any way guilty of the said felony.  So help me God, and the saints; and this I will defend against thee by my body, as this court shall award."  To which the appellant replies, holding the Bible and his antagonist's hand in the same manner as the other:  "Hear this, 0 man, whom I hold by the hand, who callest thyself Thomas by the name of baptism, that thou art perjured; and therefore perjured, because that thou feloniously didst murder my father, William by name.  So help me God and the saints; and this I will prove against thee by my body, as this court shall award."  The battle is then to be fought with the same weapons, viz., batons, the same solemnity, and the same oath against amulets and sorcery, that are used in the civil combat; and if the appellee be so far vanquished that he cannot or will not fight any longer, he shall be adjudged to be hanged immediately, and then, as well as if he be killed in battle, Providence is deemed to have determined in favor of the truth, and his blood shall be attainted.  But if he kills the appellant, or can maintain the fight from sunrising till the stars appear in the evening, he shall be acquitted.  So, also, if the appellant becomes recreant, and pronounces the horrible word of craven, he shall lose his liberam legem (free law), and become infamous; and the appellee shall recover his damages, and also be forever quit, not only of the appeal, but of all indictments likewise for the same offense.

Source: 4 William Blackstone, Commentaries *347-9.