According to John Henry Merryman, "The Decisory Oath worked in the following way: Party A could put Party B on his oath as to a fact at issue that was within Party B's knowledge. If Party B refused to swear, the fact was taken as conclusively proved against him. If Party B swore, the fact was taken as conclusively proved in his favor." Mary Gregor explains that this procedure was "designed to protect the judge from threats from the wealthy and the powerful."
^John Henry Merryman, The Civil Law Tradition (Stanford: Stanford University Press, 1969): 126, as cited in Immanuel Kant, The Metaphysics of Morals, ed. Mary Gregor (Cambridge: Cambridge University Press, 1996): 83n25 (emphasis added)