Were I certain that they did live out their lives in prison in a state of repentance and pentitance....

Were I certain that they actually cared about those they killed....

But rape is a crime of power, of control. So is serial murder. I'm afraid that the only regret of these folks would be that they cannot continue their spree of power and control.

But if society IS going to execute, then it should be done quietly and quickly, as one would clean a dirty toilet or do any other disagreeable job.