My opinion:
Death Sentence shouldn´t be allowed (no matter where). Why? Because I think, nobody has the right to take a life. And I know, murderers do that but to inflict death sentences, we (or the state) range on the same level. Maybe I would think different, if someone from my family is getting killed. That topic was discussed a lot when I went to school (especially in religion class).
@King_JCD: You say, it should be allowed, because those who are guilty should pay for their punishment in kind but I think, this
"an eye for an eye and a tooth for a tooth" mentality shouldn´t be used in the 21st century anymore.
Besides these things, there´s an economic reason to stop using death penalties.
Example: One could think, the death penalty costs the taxpayer less than a lifelong imprisonment, but afaik, this is not true. An execution costs the state (in my example North Carolina) 2,16 million dollars more than a longlife punishment. Not the execution itself is so expensive, but experts, investigations, opinions of experts and a longer taking procedure and many people are waiting years or even tens of years for their execution. Besides that, as you said, there are people who are innocent and get executed.