The death penalty: Justice or revenge?

This is a summary of what I discussed with a friend yesterday-evening.
Is the death penalty morally justified.? Supporters of the death penalty often refer to two things.

1> Punishing a murderer with a death penalty is fair. He deserves to be killed. His death will bring justice and relief to the relatives and friends of the victims.
2> The threat of death penalty is a deterrent. Potential criminals will not commit crimes for fear of being killed themselves. There will be less victims in the future thanks to death penalty.

The second point is the easiest one to discuss. The ethic of justice cannot rely on "fear". This does not mean there should not be no punishment. But relying on the death penalty to deter deadly violence from occuring is a dangerous illusion.
a. The prevention of violence can and should be based on the right understanding of the motives of criminals. Thinking that criminals "cannot be understood" is a statement of moral failure. It's an easy way out.
b. Economic motives, acts of revenge or jealousness are often quoted. Death penalty is powerless in deterring criminal acts when these acts take place in a context of poverty for example.
Do we wish our society to be at peace simply because people are cowards?

The first point is a harsh ethical one. There has been numerous cases where relatives of victims acknowledged that the death of one criminal will not bring justice.
What is justice then?
Justice takes place when the truth is uncovered during the trial.
The truth about... the innocence of the victim.
The truth about... the motives of the murderer.
Justice should also bring hope.
Hope that a communauty can find solutions to prevent another crime from happening. Hope that the causes that led to the crime can be dealt with.

Why is killing a criminal wrong?
The life of a human being is unique. Its value is beyond question. As a human being, a criminal should live to understand the suffering that he has brought to other people. Every human being has the ability to think and learn from mistakes.
The human life that the criminal has destroyed will not be gained back with the death penalty.
However, the society does have the responsability to keep criminals behind bars as long as they are a threat to other people.

Isn't killing a criminal a religious thing? Shouldn't it be the "judgement of God"?
First, the existence of God is not that obvious that we can assume a court is acting "in the name of God".
One thing is sure however. Human beings cannot "play God" by deciding who deserves to die and who doesn't. Human beings have their own limits in understanding a criminal case and in taking the right decision.

Sailom