This article is about the ability of human beings to make a deliberate choice to do evil. Punishing evildoers according to penal law presupposes that they are responsible for their acts, i.e. that they acted out of free will. In the first part I recall the origins of the classical nexus between free will, responsibility and punishment in Christian theology and scholastic philosophy. Then I analyze the philosophies of Sade and Nietzsche in order to demonstrate how the traditional conception of good and evil can be inverted. Sades extreme moral relativism and Nietzsches radical perspectivism open the gates for a justification of moral evil. In the final part I look at the serial killer as an actor who deliberately chooses to do evil. The personality disorder (psychopathy) of most serial killers probably affects their inhibition to harm others. But although their lack of empathy can lower the threshold for harming others, this (mostly) does not annihilate their moral responsibility. Such can be exemplified by the fact that many serial killers are acting in an extremely strategic, opportunistic and deceitful way in order to ensure the persistence of their deliberate choice to do evil. Moreover, some serial killers, when justifying their behavior, engage in arguments putting into perspective ‘good’ and ‘evil’ in a way that is reminiscent of Sade and Nietzsche.