Why there has some people think Capital Punishment need to be abolished?

There have some organizations want to annul the death penalty. They used two kind arguments which are Philosophical arguments and Practical arguments to support their discussion. The philosophical arguments are about “the offenders should have their human right”, “life is priceless, even though murderer’s life is the same.” The Practical arguments are about “If there have a miscarriage of justice, there cannot retrieve”, and “The prevent/deterrent function of the capital punishment has not work, the crime rate haven’t deterred by capital punishment”, “the cost for the capital punishment has spend too much money”