This theory for the selection stage of capital sentencing has three interdependent parts. A death sentence is valid only if a competent sentencer acting responsibly makes the moral judgment that the defendant deserves execution. The quality of mercy is the common denominator. To increase the likelihood that a sentence will accurately convey community standards of retribution and mercy on the facts of each case, a capital accused has the right to be sentenced by a jury (one that is not death-qualified), the jury must decide sanction without reference to the possibility of future revision, the jury must be offered an acceptably severe noncapital alternative, and the selection between life and death must be based solely on the historical facts of the defendant's crime and life. A theory of capital sentencing built around the due implementation of the community's standards of retribution and mercy will not yield precision in selection from the death eligible pool, but it will encourage punishments calculated to convey 'the evolving standards of decency that mark the progress of a maturing society.' 463 footnotes. (Author summary modified)