The use of ordeals and sworn oaths to prove one's innocence invites trickery. The guilty trickster cannot influence the judgment of the divine powers, but he can—by disguise or by equivocation in wording the oath—create a presumption of innocence. Ralph Hexter surveys the varieties of such stories in a number of folk literatures and looks at the use of this motif in three important medieval story cycles, with special attention to the way Christian writers handled story material based on a pre-Christian act of truth.