There have been sixteen people wrongly sentenced and put on death row. They were later exonerated by DNA tests that were done after the fact. Had they not had anyone to make the effort to fight for more evidence, then sixteen innocent people would have been put to death.
Are willing to play those odds? I'm not.
The death penalty is archaic and barbaric. As the slogan goes: "Why do we kill people who kill people to show that killing people is bad?"