Asguard,
I see your thoughts of wanting to keep from killing as commendable. I do not, however agree with them and especially some of the other thoughts you have laid down.
Ethics say killing is wrong in all sences, so using death penelty is wrong because its killing (in cold blood)
Culture and majority determine ethics. (Just like sanity) Crimes that carry the death penalty are for the most serious of offences. How does the family that lost a loved one console themselves to living with the idea that the perpetrator that wrecked their lives is living and will be in some cases back on the block in a matter of time? Their family member is gone never to be able to return to them. Why should that one, who caused their misery and grief, be able to profit by it later on in life? It sounds as if you say that the killer is more just because he will see many more days, while his victim has no voice to speak of the agony of his own death. Was the victim any less right because he is dead?
the more people in a sociaty (working profitably, not in jails) the better sociaty is as a whole, economicaly
If giving people jobs would eliminate crime then I would be all for it. People in jail are there because they could not live by society rules. Plain and simple. So how do you teach them it is wrong? Hollering at them is not going to do it. If you propose to have everyone working and no one in jail then you must have a near perfect deterrent. (One that works!) You will have to come up with what works to allow such people back into society; else you may be the next victim. Economics is not all the story. If it was, when some one was found guilty of any crime that meant imprisonment they would be shot to keep from having to spend money on them to feed, cloth, and house them.
This one is debatable but Christianity says that anyone can change, there is no point of no return, other religions maybe different
So how many do you allow the killer to kill before you decide that maybe he will never be able to interact with society. After the first death, if you do not stop the behavior, it will at some time resurface again. How would you feel if it were your son that was killed as the second victim after he had already been caught.
sociaty runs more smothly when people are happy and killing its own citisens or locking them up for long periods of time for mestakes you are breeding desent
Here we run into which is more deserving, the killer free to terrorize those around him or society, who is the victim? If you let the killer remain at large it will promote hysteria among those who are innocent and there are far more of them then there are of killers. Look at all the stuff that went on when Son of Sam was on the hunt. Or Jack The Ripper. Both are famous serial killers.
Long jail terms have a tendancy to make people re-offend
I will not argue this point. What would you suggest to take its place?
science says that we should treat criminal behavior as a mental illness and try to cure the criminals
And how do you do that? We have tried jails, rehabs, institutions, but no single treatment works. Really seems to be effective in all round use it needs to be. A lot of this also depends on the individual. Rehabs returning to jail are just as high as ever because the rehab didn't take.