I'm for it. On several levels.
To get this one out of the way, the religion level: Whomever sheds the blood of man, by man shall his blood be shed. Genesis 9:6.
Now... to the constitution. If you ask me, "Cruel and unusual" is subjective.... Cruel moreso than unusual... because "unusual" is mostly a matter of how often it's done.
If something is cruel but usual... it isn't cruel AND unusual... personally, for those who kill and/or mutilate one or more people, an injection to the arm or several thousand volts of electricity is far from cruel.
Also.. regarding the 14th amendment:
nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
This tells me that WITH due process of law, any State may indeed deprive a person of life, liberty, or property (obviously not in that order).
In general... a nation governed by laws of right and wrong must punish wrongdoers... otherwise, calling something "wrong" is empty and meaningless.
So.. the murderer who murders in prison... how do you punish him... more prison? That's like splashing someone in a swimming pool... they're already wet... you're not really doing anything.
Murderers have proven that they have no regard for the law or the people it is designed to protect. They are unworthy of the oxygen they breathe. They are unworthy of the food that my tax dollars pay for. The medicine that is used to treat them should be going to law abiding citizens who need it.
I know people who make just enough money to not be thrown out of their house and to eat on a daily basis, and need medicine that costs several hundred dollars... and they have to do without medicine because they can't afford it. Yet the man who kidnapped an entire family, raped the women, mutilated the men, then killed and dismembered the women in front of their children.... they get medicine, and they don't have to pay for it.
Is that justice?
In my personal opinion, I think the methods of execution should be:
Firing squad
Electrocution
Guillotine
One gunshot to the back of the head.
The use of any of the above to be determined according to the severity of the crime for which the condemned is being executed.
It should be publicized, and on the television screen, scrolling across the screen continuously should be the crime for which the person is being executed for. The victim's name, age, and manner of death, so that the whole world knows exactly why this person is being executed.