Barnes v. Marshall
Supreme Court of Missouri
467 S.W.2d 70 (1971)
After Dr. Marshall's death, his daughter Jill Barnes (plaintiff) challenged his will, which favored outside organizations and individuals over his immediate family, presenting extensive lay testimony that Marshall believed God spoke to him directly, called himself a prophet, ran for President and Congress on instructions from God, and displayed bizarre and erratic public behavior, along with two doctors' testimony that Marshall suffered from manic-depressive psychosis. The jury found the will invalid for unsoundness of mind, and some beneficiaries (defendants) appealed, arguing the evidence showed mere eccentricity, that Marshall executed the will during a lucid interval, and that lay witnesses should not have been allowed to opine on his mental soundness.
Whether a will is invalid if the testator was not of sound mind when the will was executed.