"Death is an unusually severe and degrading punishment; there is a strong probability that it is inflicted arbitrarily; its rejection by contemporary society is virtually total; and there is no reason to believe that it serves any penal purpose more effectively than the less severe punishment of imprisonment. The function of these principles is to enable a court to determine whether a punishment comports with human dignity. Death, quite simply, does not. When this country was founded, memories of the Stuart horrors were fresh and severe corporal punishments were common. Death was not then a unique punishment. The practice of punishing criminals by death, moreover, was widespread and by and large acceptable to society. Indeed, without developed prison systems, there was frequently no workable alternative. Since that time, successive restrictions, imposed against the background of a continuing moral controversy, have drastically curtailed the use of this punishment. Today death is a uniquely and unusually severe punishment."