There is more to be said. Thoughtful writers have contended that the death penalty, besides being unnecessary and often futile, can also be positively harmful. Four serious objections are commonly mentioned in the literature.
There is, first of all, a possibility that the convict may be innocent. John Stuart Mill, in his well-known defense of capital punishment, considers this to be the most serious objection. In responding, he cautions that the death penalty should not be imposed except in cases where the accused is tried by a trustworthy court and found guilty beyond all shadow of doubt.
It is common knowledge that even when trials are conducted, biased or kangaroo courts can often render unjust convictions. Even in the United States, where serious efforts are made to achieve just verdicts, errors occur, although many of them are corrected by appellate courts. Poorly educated and penniless defendants often lack the means to procure competent legal counsel; witnesses can be suborned or can make honest mistakes about the facts of the case or the identities of persons; evidence can be fabricated or suppressed; and juries can be prejudiced or incompetent. Some “death row” convicts have been exonerated by newly available DNA evidence. Columbia Law School has recently published a powerful report on the percentage of reversible errors in capital sentences from 1973 to 1995. Since it is altogether likely that some innocent persons have been executed, this first objection is a serious one.
Another objection observes that the death penalty often has the effect of whetting an inordinate appetite for revenge rather than satisfying an authentic zeal for justice. By giving in to a perverse spirit of vindictiveness or a morbid attraction to the gruesome, the courts contribute to the degradation of the culture, replicating the worst features of the Roman Empire in its period of decline.
Furthermore, critics say, capital punishment cheapens the value of life. By giving the impression that human beings sometimes have the right to kill, it fosters a casual attitude toward evils such as abortion, suicide, and euthanasia. This was a major point in Cardinal Bernardin’s speeches and articles on what he called a “consistent ethic of life.” Although this argument may have some validity, its force should not be exaggerated. Many people who are strongly pro-life on issues such as abortion support the death penalty, insisting that there is no inconsistency, since the innocent and the guilty do not have the same rights.
Avery Cardinal Dulles, “Catholicism & Capital Punishment” (2001)