capitol punishment

I am truly against it. No matter how many reasons I hear people bringing that it should exist and that it makes the legal system strong I can't convince myself. I can think of two groups of reasons why I am against it:

• Faultiness of the decision due to human errors
• General critique

Faultiness of the system:

• The system is unfair, who gets to make such a decision? In other words, who gets to be God?
• It can never be determined whether it was a true crime or not - even in spite of a guilty plea.
• It can never be determined how much of the fault the person was actually responsible for and how much of what lead to the crime is the person to be punished for.

I don't mean to question the penal system, I just think taking a person's life is not an option, it's just too much to decide for.
General critique:

• Can't take what you didn't give.
• It's punishment with what you are punishing for - same, same.
• Uncivilized and barbaric.
• Not really getting back at the person for what they did - someone who killed 300 people will be punished the same as someone who killed one.
• What's wrong with life imprisonment? What good does it do to kill another person? I can't accept the debt on tax payers money argument on this. Worst case, we can think of them as a portion of the community who require special treatment. They deserve a share of society.

For crimes that are reversible to some extent, such as robbery, the punishment is straight forward. But in hate crimes, mental and physical abuses, or murders, we are dealing with a much more complicated situation. Assuming we can even determine to what extent the accused should be charged, we still have to develop a more flexible prosecution system ...