insane delusion

Insane delusion is the legal term of art in the common law tradition used to describe a false conception of reality that a testator of a will adheres to against all reason and evidence to the contrary. A will made by a testator suffering from an insane delusion that affects the provisions made in the will may fail in whole or in part. Only the portion of the will caused by the insane delusion fails, including potentially the entire will.  Will contests often involve claims that the testator was suffering from an insane delusion.