Death penalty: a reasonable measure?

Countries such as USA, Iraq, Jamaica, Japan, Guatemala, Iran, Korea, Thailand, India and others still practice the death penalty in their countries, they are almost 90 countries.

In Chile, death penalty was abolished in 2001 and was "replaced" by 40 years in prison as maximum. I said that was "replaced" because now 40 years is the most severe punishment that a criminal can receive, this new measure is called: qualified life imprisonment, wich states that the criminal can't have access to any benefit for 40 years. But I wouldn't call it "life imprisonment", because that means that the criminal must remain in prison for the rest of his/her life, and this sentence it's just for 40 years in prison... but it's true that 40 years in prison plus the age that the criminal has, it's almost all his/her life, so the criminal will be very old when the sentece has ended or will die in prison. But this sentence, in Chile, is just for murderers, not just for them, what I'm trying to say is that all the murderers receives this sentence, in other crimes it depends on many other things. So if you kill somebody, you'll be in prison for 40 years.

In countries like Usa, death penalty it's called "capital punishment" and it applies only for aggravated muder and more rarely fenoly murder or contract killing. It is just legalized in some states, but in the most of them. I've read that in some states they don't follow all the legal procedures before condemnig the criminal, that means that maybe the "criminal" can be totatlly innocent. And I've also read that sometimes they are very racist, I mean for example if someone kills a white person, the criminal will be immediately sentenced, but if the victim is a black person, maybe the criminal can be released. That is not what we call justice.

In many countries where death penalty exist evidence shows that capital punishment does not deter people from committing crimes, in fact, a study found that certain types of muders increased after the reintroduction of capital punishment.

So... should death penalty exist? to my mind YES, but ONLY in some cases. People who is against says that criminals have the right to live, things about respect for life, that killing it's a sin and things like that (and I respect that), people who says that are mostly religious people. But there are some people against death penalty that says that this sentence it's like a "gift" for the criminals, they think that maybe the criminals feel guilty (sometimes) and they feel so bad, that there's nothing better than dying, or that they prefer dying than spend almost the rest of his/her life in prison. This kind of people think that criminals should suffer, and to be honest I'm totally agree with them.

What if a man with only 25 years old kills a woman, and then is sentenced to prison for 40 years? After the sentence he will be 65, 40 years are enough time for changing the way of thinking of a sick person? I don't think so, I think he should be forever in prison. But why should the government spend money in prisons? If the criminal will never change, why should we keep them with life? we shouldn't, but they do must suffer. What I just said was only regarding murderers and rapists.

In my opinion, the government should use criminals for making hard works, cleaning the streets, cleaning rivers, I don't know, in many things. But I'm not agree with the fact that they just spend the sentence in prison, doing nothing productive for society. I reckon that many of them can change, but they must be at prison at least, I don't know, 3 years, because nobody can change so fast. So I think there must exist like a "minimum sentence" for all the criminals that are not murderers.

And I'm also in disagree when murderers and rapists in Chile don't stay in prison the 40 years, or they receive a shorter sentence, and just because "they aren't in optimal mental conditions" or "they didn't know what they were doing", of course they aren't in optimal mental conditions if they did what they did, they are sick and they will be always sick people!!. If someone kills someone, this person must stay in prison for 40 year, no less.

I'm in favor of death penalty, but JUST when the person killed or raped someone, and JUST when one of her/his organs can save somebody's life.