3)The innocent can be wrongly put to death.
Conclusion: Capital punishment should be abolished.
Though capital punishment might seem like the only way to get revenge, it is morally unjust. Who are we to decide whether a person should live or die? It is morally wrong, individually or through government action, to seek revenge on a murderer by means of execution. The death penalty violates our right to life. Capital Punishment is Not an Effective Deterrent
As justification for capital punishment, deterrence is used to suggest that executing murderers will decrease the homicide rate by causing other potential murderers not to commit murder from fear of being executed themselves and obviously the murderer who is executed will not kill again. This position may seem initially correct, and indeed, in a USA Today Poll, 68% of respondents agreed that the death penalty is an effective deterrence for crimes. However, some research suggests that rather than deterring homicide, state executions actually may cause an increase in the number of homicides (Stack, 1990). This phenomenon has been called the "brutalization hypothesis" and it suggests that through proposition, modeling, or by legitimizing killing, the death penalty actually causes an increase in homicides. Thus, the brutalization hypothesis is a reason for opposing the death penalty.
On the other hand, a study prepared for the UN in 1988 showed that abolishing the death penalty shows no significant change in the number of crimes...