I verified what I posted earlier here:
http://www.nyodn.org/organ/o_donationfacts_faq.html Q: When must organs be removed?
A: Organs must be removed as soon as possible after the determination of brain death, while circulation is being maintained artificially. Tissue may be removed within 12 to 24 hours.
I'm baffled by your question. If you are asking about a kind of donation that does not require the death of the donor, I think that could be allowed. If the person wishes to donate a kidney or blood, I don't see anything wrong with that. But by law, that person must be executed by electrical chair, which would cause his/her heart stop and he/she does not technically have a brain death to be qualified to donate his/her vital organs.
When you declare you are an organ donor, you acknowledge that
in case of brain death, your vital organs can be taken for transplant purposes. A person on a death row on the other hand, will not experience brain death by execution means, and it is not as if any of us could choose how we are going to die. Furthermore if such a thing becomes a law, family members of the victim who are going to witness the execution, if there should be any, must be able to have a say in this matter.