I am new here and will not bother reading these 13 pages of text (forgive me!), but if anyone is interested, I rest here my opinion:
The death penalty is good for murderers with intent.
If criminal X has been planning out a string of murders for the past six months, and then goes out and kills a bunch of people, and he is sane, he deserves the death penalty.
If regular citizen Z had a knife by him, and in a fit of rage, killed someone he was arguing with, then he deserves the death penalty.
By man-slaughter is not murder. Man-slaughter is unintentionally and without malice, usually. This type of killing needs to be punished to an extent, but the death penalty, or a lifetime in prison are not the ways to do it.
Accidents happen. I spill my water bottle, and there is no retribution.
I accidentally kill someone, and now I face serious damage.
But why? The intent on my part was the same for both, yet the outcomes were different. I do not believe there is a God, nor is there such thing as karma (read very bottom of post for my view on karma, if you want). And so, I don't think that because I killed someone, I deserve to die. The family is surely angry and demands some sort of revenge or retribution, but really, I am at no blame here. It would be unreasonable to punish me severely.
This is an entirely different case if, say, I was drinking while driving, not paying attention while driving, not being careful while using a gun, etc. This needs to be punished because, 1) if not, people will stop having to worry about being wary and attentive, and 2) because not being careful is not a good enough excuse. However, because slip-ups can happen, punishment shouldn't be serious; perhaps a hefty fine or a bout in prison would be reasonable.
KARMA:
Karma does not exist. Society just awards good deeds well, and punishes bad deeds justly. Karma, in a way, occurs through society, but it isn't constant or eternal. It does not stalk and keep track of you, making sure retribution is served.