This is of course quite ironic as Bill of Rights was largely designed to safeguard human rights but taking somebody's life forcefully is no way serving human rights and in order to maintain human dignity there is need to revoke the capital punishment altogether and this must be assured in the constitution just as done by all the countries of European Union. For this very purpose the amendment eighth could be made complete by stating that no cruel and unusual punishment including death sentence for the guilty. Amendment IX: [1]

The assigning of numbers to rights in...

The amendments of the Bill of Rights serve to safeguard the rights of people which might be ignored or even denied through the misinterpretation of law in the absence of such provisions. So they play vital role in defining and establishing the basic rights of individuals to which they are entitled to on the account of common denominator of humanity.
Reference:

Timothy M. Helmus, Val E. Arnsdorf, Edgar a. Toppin, Norman J.G. Pounds. (1984)

The World and Its People, the United States and Its Neighbors. (p.p 120-123)

Silver Burdett Company 17-205 00, ISBN 0-382-02833-3