Dahlia Lithwick discusses an apparent case of an actual innocent man being executed here, I first hearing about that particular case in this podcast. A taste of her article:
But you needn't take Grann's word for it. In 2004, Dr. Gerald Hurst, an acclaimed scientist and fire investigator conducted an independent investigation of the evidence in the Willingham case and came away with little doubt that it was an accidental fire—likely caused by a space heater or bad wiring. Hurst found no evidence of arson and wrote a report to that effect to try to stay the execution. According to documents obtained by the Innocence Project, it appears nobody at the state Board of Pardons and Paroles or the Texas governor's office even took note of Hurst's conclusions. Willingham was executed by lethal injection, telling the Associated Press before his death, "[t]he most distressing thing is the state of Texas will kill an innocent man and doesn't care they're making a mistake."
As long as capital punishment exists, this will be a possibility.* And, we do not know this only from DNA evidence ... in fact, in many cases, DNA evidence will not be available to find innocence. The problem, of course, is deeper than this one issue. As Justice Stevens noted:
current decisions by state legislatures, by the Congress of the United States, and by this Court to retain the death penalty as a part of our law are the product of habit and inattention rather than an acceptable deliberative process that weighs the costs and risks of administering that penalty against its identifiable benefits, and rest in part on a faulty assumption about the retributive force of the death penalty
The case of Troy Anthony Davis underlines the point. The matter was sent back to a lower court. But, the lower court is restrained in its discretion. This is underlined by the dissenting opinion in Herrera v. Collins, the case cited in the article the left open the question of executing an innocent person. Remember this is Justice Blackmun, who shortly after declared the death penalty as a whole unconstitutional:
The government bears the burden of proving the defendant's guilt beyond a reasonable doubt, Jackson v. Virginia, 443 U.S. 307, 315 (1979); In re Winship, 397 U.S. 358, 364 (1970), but once the government has done so, the burden of proving innocence must shift to the convicted defendant.
This is no easy task. But, clearly, trial judgments are not perfect. Some innocents are convicted. This is horrible in respect to any crime, particularly those with long sentences in our less than ideal penal system. It is a risk we have to take, since we need to protect ourselves. OTOH, execution is not needed for that. In fact, often it is based surely on retribution.
This is a questionable ground by any metric, it surely is to the degree that the system risks executing innocent people. Which is but one problem with capital punishment. BTW, Scalia says innocents are weeded out. Of course, this includes by a mandatory system of due process and post-conviction review of a sort that he finds unnecessarily elaborate.
To be honest, I do not feel the presence of innocents to be the be all, end all reason against the death penalty. Rather, I do not think -- though it is compelling for many -- the presence of factually innocent people executed will do the trick. Perfection in the area of things that can lead to death is impossible, but we still take that risk. I do think the system is too arbitrary -- given what juries believe "deserves" execution, too many are given it that would not be if an evenhanded, not so error laden system was in place. In effect, "innocent" for the purposes of execution can be a broad matter.
And, it is clearly one more brick in the wall.
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* Sen. Thurmond (the one Trent Lott wanted to be President) once put forth a report that quite honestly admitted the fact, but -- as some who are honest will agree with -- argued that the risk is worth it overall. That is, no penalty system is perfect, but the death penalty is necessary overall, so cost/benefit wise, a few rare innocent executions is a necessary evil.
To the degree that some have been wrongly in jail for decades, this is not as outrageous as one might think, I guess. In fact, some believe we have too few executions in this country, something that led Justice White to vote the way he did in Furman v. Georgia:
I begin with what I consider a near truism: that the death penalty could so seldom be imposed that it would cease to be a credible deterrent or measurably to contribute to any other end of punishment in the criminal justice system.
White changed his vote later, but the fact states reaffirmed that the possibility of execution should exist really did not change the situation too much. Maybe that is why Stevens cited White in his own opinion cited above ... the principle still is abolitionist in practice.