The Pennsylvania Supreme Court has held that insanity is a defense to murder, but was unable to come to any agreement as to the effect of the presumption of sanity, and the burden of proving sanity or insanity.
Commonwealth v. Vogel, 440 Pa. 1, 268 A.2d 89 (1970).
The defendant, Dennis Vogel, shot and killed two persons while carrying out an armed robbery. At his trial, he pleaded not guilty by reason of insanity. The defense presented four eminent psychiatrists to establish Vogel's legal insanity in accordance with the M'Naghten rule. The commonwealth offered no testimony to rebutt or impeach the testi mony given by the witnesses for the defense. Instead, the commonwealth relied soley upon the presumption of sanity, and upon the testimony of witnesses as to the circumstances surrounding the robbery and killings. Vogel was subsequently found guilty of armed robbery, as well as two counts of murder in the second degree. In a five-two decision, the Pennsylvania Supreme Court reversed his conviction, and a new trial was granted. Four separate opinions were filed by the members of the court. Three opinions in support of the order for a new trial, and one dissenting opinion.
Ronald C. Mokowski,
Criminal Law - The Presumption of Sanity - Burden of Proving Sanity or Insanity,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol9/iss2/15