Death penalty doesn't do anything else other than more violence.
Maybe it costs less than keeping them in jail, maybe its easier, for some a relief and for others it may be revenge or pleasure.
Thing is - we're humans and regardless we still proceed to hurt one another. If you want to fix this - killing even more of us isn't going to fix the problem - that way you'll just make it worse.
It may be a solution to some; but there's nothing to do about it and I am nearly guaranteed it hasn't and won't work as it's been proven in the past.
How do we know what could "Death penalty" applied to and for? Some may say Murder, rape; etc. But how do we know we'll keep it under control? How do we know who keeps it within the boundaries?
In some countries, being homosexual would receive the same penalty as being a rapist and it is considered to be in the same category. Today, we would start with murderes; tomorrow with rapists; after that with homosexuals - and in the future you'll be sentenced to death penalty for just not agreeing to a certain president, state, or religion.
We need to grow out of this and work all together - people can be fixed and people can change. Some things come from the childhood or a wrongfully done path of learning; we need to learn to correct these people as we should all have a fair and equal chance. Crime I doubt will ever stop - we shouldn't worry about what to do with the criminal after the crime has been done, we should worry about how to prevent the crime from happening at all.
Killing someone won't bring you a loved one back, and it won't make the others stand back - you'll just instead make them angrier or have more of a purpose against you and/or whoever it is.
Some may say Prison doesn't work, but that's because Prison isn't and hasn't been set up properly in the past few years - it shouldn't punish, it should teach and reconstruct a person back to it's morals; it should try to make the person see what was wrong and not to do it again, or ever; or even know not to do it in ever in the first place. We can never be 100% sure if the person is actually guilty, and innocent people can always die - once again, we're never sure.
We can't control power, and killing someone would make us just as "bad" as the person we'd be sentencing.
This of course can be taken and moved back and forth inbetween many many different perspectives - and it requires a lot of analyzing - but I believe this to be the right way to think of it and see it. Please correct me if I'm wrong or if you think otherwise. I'd be glad and interested to hear & know.
Thanks you very much, and wish you good luck.