The European countries for example, have recognised the human rights in 2000 and the majority of European people thought that death penalty is wrong. In my case i been also influenced by religion matters, but as i said i oppose the death penalty and i’d rather not live in a country where the government feels empowered to kill people.
In my opinion, the death penalty is about serving justice and not about deterrence, it is not about saving future lives. Let's take the USA for example, is not been demonstrated that the death penalty has stopped murders, and like USA so the others countries like China and Iran have still highs numbers of murdering.
Another reason to oppose the death penalty is because it is not an equal instrument of judgement. In short, if you are wealthy you will not get the death penalty, but if you are poor (and often, a minority), your chances are much higher.
I can finally say that murders should not be executed because i think that death penalty does not deter criminals more than life imprisonment, and it just encourages a "culture of violence" in our society, life must be respected in any case.