A powerful argument for reserving capital punishment for murders is “marginal deterrence.” If assault were punished with execution, perpetrators would have an incentive to kill their victims to avoid discovery (which is a major reason why the severity of punishments more generally should be matched to the severity of crimes).
给杀人犯保留死刑的一个强大的理由是“边际震慑”。如果用死刑处罚人身攻击，那么罪犯就有动机杀死其受害者来避免被发现（这也是处罚的程度一般应当与犯罪的严重性相匹配的主要原因）。