If I may digress, while I am an opponent of the death penalty, I think there's a compelling argument that it's misused by only being applied in cases of murder. Murder has a significantly lower rate of recidivism than many other crimes, particularly (relevant to this discussion) sex crimes. Among sex criminals, the category of offender most likely to re-offend is men who rape adult strangers (contrary to the common misconception that child molesters are the likeliest). Also, sex crimes have a much longer "tail" than murder, in that the victims are themselves likelier to commit crimes and/or suffer from mental illness and addiction, whereas murder victims are, by definition, not going to hurt anyone or suffer any longer.
I have always thought the same thing. I know a violent rape survivor and she calls the day she was raped the last day of her life. She's been in and out of rehab for drugs, was at one point prostituting herself just to get high and to this day has some serious mental problems. Luckily she finally found a husband who ensures that she gets the quite extensive and lifelong mental healthcare that she needs but in her case there is an argument that it would have been better for her had he just killed her. Yet the offender got a sentence lighter than most murders committed as crimes of passion. The murderer only committed the act because of a very special circumstance and isn't likely to do it again. I can't say the same for the rapist, he basically picked her randomly so he is surely going to be in the same position again.
I'm personally not a fan of the death penalty, especially as we currently do it. It costs more than just locking them up for life and we have gotten it wrong before many times that we know and surely many times we don't. Wrongfully killing someone is by definition murder and we put people in jail and to death for it but when the state does it they just say "ooops, our bad".... With enough evidence to know 100% sure and beyond all doubt, much more than simply beyond a reasonable doubt, I would be for it. BTW, relying on only eyewitness testimony is NOT beyond all doubt, this has been proven fact. In those cases, again beyond all doubt whatsoever, skip all the bullshit and hang them within a few months of sentencing. Save the rope for reuse.