Serial killers do what they do precisely because it is the one area of life where they have power.
Their traumatic childhoods made them feel powerless, and they turn to serial killing as a way of affirming their ability to control their own lives.
So serial killers are actually hyper-responsible for their actions, since they not only commit them deliberately but with the very intention of consolidating their ability to act deliberately.
Proof of this is the extraordinary amount of planning they put into executing and then covering up their crimes. Their crimes are exercises in self-mastery.