In terms of what Aristotle says about voluntary actions, we are clearly responsible for any actions we intend. If someone murders someone else for vicious reasons, through the vices of spite, malevolence, hatred, envy, jealousy, anger or lust, then then this is simply a matter for justice. A person of practical wisdom behaves justly quite simply by obeying the law and by being seen to obey it. For somebody who voluntarily and viciously disobeys the law by murder, then justice really requires restoration in kind, which requires capital punishment. This is not an issue of choosing between retribution and deterrence on the one hand or reformation on the other