1. Power corrupts. No person or government should have the right to kill a person in cold blood
2. Death penalty jurors are more likely to wrongly convict, leading to high rates of wrongful conviction.
3. Innocent people may plead guilty to serious crimes, to avoid the risk of being wrongly convicted and executed.
4. Distortions can occur – example Charles Boney would not have been protected by his mother were it not for death penalty => David Camm would not have spent 13 years in prison.
5. Violence leads to more violence. Prisoners on death row are a danger to others.
6. Extinguishing hope is cruel.
7. Jurors (and others) may be mentally affected by having to make life’/death decisions. Also prosecution and defense attorneys, judges, executioners. Few people want to do the work.
8. Death penalty prosecutors seem particularly stupid and corrupt ( in Arizona and Texas, the record is very bad ).
9. There is always the chance of an innocent person being executed, many innocent persons have been executed in the United States.
10. If the state/government kills in cold blood, that promotes the idea that killing is acceptable in weak minded people. Again, violence leads to more violence.
11. Killing mentally ill people is wrong. Most people on death row are either mentally ill or were mentally ill at the time they committed the crime, taking a fairly broad view of mental illness.
12. Trying to kill a really clever psychopath is a doubtful idea, they may cause all sorts of damage when you attempt it. Better to be kind to them, but keep them safely locked up.
13. The death penalty is harmful to the family of the victim : see The death penalty and victims of crime.
14. The family of the convicted person also suffer – even though they have done nothing wrong.
15. It is very expensive, it is not evenly applied and is used for essentially political purposes, to satisfy the blood lust of ignorant sections of society. There is no evidence it has any deterrent effect.