Matthew McDavitt, Senior Attorney, National Legal Research Group
While the issue is apparently one of first impression in many jurisdictions, a handful of courts nationally have addressed the relevancy and admissibility of evidence of pre- or post-will-execution mental capacity—normally deemed irrelevant to will-execution mental capacity—where it has been shown that the testator suffered from a permanent mental deficiency. Importantly, as observed by the U.S. Supreme Court, where evidence is developed of permanent or continuing mental incapacity, the burden properly shifts to the will proponent to prove a lucid interval, rather than the normal burden upon the contestant to prove incapacity, as continued mental incapacity is legally presumed:
In addition to the proof . . . of his undoubted insanity prior [to] and for some time subsequent []to [the will execution], there was slight evidence of insane acts during the month of February, though there was no opinion expressed by anyone that he was incapable of making a valid deed or contract. The whole testimony regarding his insanity was duly submitted to the jury, who were instructed that if they found his insanity to be permanent in its nature and character, the presumptions were that it would continue, and the burden was upon the defendant to satisfy the jury by a preponderance of testimony that he was, at the time of executing the will, of sound mind. There was no error in this instruction.
Keely v. Moore, 196 U.S. 38, 46-47 (1904) (emphasis added).
Read More