Life and Death Row: Is The Death Penalty Moral?

It's a VERY tough question  to ask....is the Death Penalty moral or not?
There is a saying, from the Bible I believe, but don't quote me on it as I am a thorough Atheist; 'an eye for an eye and a tooth for a tooth' that suggests some kind of karma. You get what you are given. If you kill someone, you should die.
But what about the expression 'two wrongs don't make a right?'
Is killing a killer just as wrong as the killer was to kill someone? (I have written killer too many times now!) The killer/convicted murderer has family and they will have to suffer and become bereaved if the prisoner is killed. But the family of the victim also had to suffer and grieve.
It is a VERY raw, delicate and debatable subject.....
I don't know how I feel about the Death Penalty. This post was inspired after watching the third episode in a 3-part BBC TV documentary on 'Life and Death Row.'
The thing that creeps me out is that, at the time of filming Robert Pruett's execution date was set for, I'm not sure what month, but summer 2013. The crisis team managed to appeal a 60 day postponement in the execution date, which could be up to two years as they were re-testing DNA samples from the crime scene that could change the murder 'theory' completely. It is has obviously become a 3 year wait as Robert's execution date is April 27th 2016 (and watching the documentary, filmed in 2013, it said the date would be April 2016), it was only broadcast in 2014, so I'm not sure how it popped us as a most recent documentary. I think it was on an advert break when I was watching BBC's (1 of 4 part independent episodes on mental health) Life After Suicide .
Anyway, sorry I went off topic, so...the freaky thing is that it is now THE year of his execution and next month it will take place. Also, my dissertation is due in on 27th April (that's the deadline, which is darkly humorously ironic.)
But seeing Robert talk he didn't look like a murderer, but what does one look like?
I just feel that killing a human (because they killed a human) is wrong and a vicious circle as whoever injects the lethal dose of whatever it is they give them to kill them, maybe they are then a murderer?
Also, what about cases that, after the prisoner has been killed, it comes out that they are innocent.
Killing is a bad thing so killing a killer is encouraging killing!? (Too much killing again!)
I just feel everyone deserves a second chance and a right to live, to some degree. However it is hard, like, for example: I would wish Hitler dead, I would wish someone if they were to kill a member of my family dead, But then could I seriously think about the murderer's family and how they felt or would my own grief and anger blind me?
Perhaps, if it is proved 100 per cent, which is near enough impossible, someone who murders in cold blood for no reason and shows no remorse should die.
But not someone who was having a fight and hit too hard, or someone who got involved with the wrong people and was pressured into fighting people and ended up killing someone. Not someone who is VERY mentally ill, as they lack capacity, so technically they didn't 'do it' because they weren't 'all there' at the time.
Anyway, rant over, with not much of a conclussion, but an interesting subject and was enjoyable writing a blog post again. Try watching the Life and Death Row series and see what you think?!...