DNA Reminds Us That to Err Is Human

Professor Brandon Garrett’s essay highlights lessons we can learn from DNA exonerations of condemned prisoners. Ultimately, some of the most important issues are about what the exonerations tell us about the capital punishment process. His essay raises several questions, including what is the significance of the quality and number of exonerations, how legislatures should respond to the exonerations, and what the exonerations teach us about non-innocence issues.

How Many Mistakes?

Innocence arguments probably go back to the first execution, with death penalty advocates and opponents debating how often innocent people are convicted. For example, in 1935, a writer in The New Yorker discounted the risk of wrongful executions, noting, “The vision of American criminal law as a ravening monster, forever hounding innocent people into the electric chair, is one with which emotional persons like to chill their blood. It is a substitute for tales of ghosts and goblins.”[1] Similarly, Joshua Marquis here and elsewhere has attacked the popular perception that innocent defendants are often convicted,[2] and Garrett notes that death penalty advocates have argued exonerations are rare. Meanwhile, others have suggested the numbers of wrongful convictions are more significant.[3]

Beyond the numbers, both sides argue about whether or not specific exonerated individuals were actually innocent. And at least one death penalty advocate would debate Garrett’s example of Kirk Bloodsworth as a death penalty exoneration, not because of guilt, but because Bloodsworth was no longer on death row by the time he was exonerated.

While death penalty advocates and opponents debate the numbers and how much weight to give specific cases, at some point the arguments distract from the underlying concern. Nobody doubts there are wrongful convictions and that a number of exonerations occur because of luck more than anything else. For example, Illinois discovered a number of innocent defendants on death row because of the fortuitous work of Northwestern University journalism students. And not every case has DNA evidence. While Innocence Projects and similar organizations have successfully exonerated a number of condemned individuals, other capital defendants who may be innocent but whose cases lack DNA or other similar conclusive evidence may find little help.

Like all endeavors, operating a criminal justice system must involve some risk. Although DNA evidence has exonerated several capital defendants, the numbers are a small percentage of all capital defendants. And the fact that the system finds the errors arguably shows that the system works, at least eventually. Yet we do not know how many innocence cases are not discovered, and it is a mistake to believe that DNA gives us a key to determine guilt with complete accuracy.[4]

In my criminal law class, I ask my students how much error they think we should tolerate in a criminal justice system and what percentage of wrongful convictions is acceptable. 1 in 1,000? 1 in 10,000? 1 in 100,000? In an ideal world, there would be no errors, but in our imperfect world there will always be errors, as Joshua Marquis correctly notes about all human activities where we tolerate risk, such as surgeries.

So, when the federal and state governments take these risks with the lives of its citizens, the question comes down to a balancing of costs and benefits. If one sees a great value in having the death penalty, one may tolerate some risk of error, where if one sees little or no value, one may tolerate less or no risk. Some may see some benefit, as where Mr. Marquis cites Prof. Cass Sunstein’s article arguing that some recent studies might indicate the death penalty saves lives. But others might argue the use of capital punishment increases violence or point to scholarly articles that debunk the research mentioned in Prof. Sunstein’s article.[5] Still, even if one agrees with most criminologists that the death penalty does not deter better than life imprisonment,[6] a death penalty advocate may respond that there are other benefits worth the risk of wrongful convictions. And these arguments will not be solved by DNA.

What Reforms Are Needed?

We need additional protections in the system to decrease the number of innocent people being sentenced to death. Garrett explains that faulty eyewitness identifications have led to some wrongful convictions, and there is a growing amount of scholarship on the problems of eyewitness identification. For example, one study of forty inmates who were exonerated by DNA evidence found that 90% of their trials included faulty eyewitness evidence.[7]

Reforms are a good starting point, but they may be difficult or costly to enact. Marquis is correct in his essay that prosecutors are in an important leadership position and play a key role in improving the system. For example, a few days ago a group of eleven current and former Kentucky prosecutors wrote an op-ed calling for reforms to Kentucky’s death penalty and a moratorium on executions until the reforms are implemented.[8]

Policy makers may respond to the DNA exonerations in several ways, such as (a) deciding the current low level of risk is acceptable; (b) finding the current level of risk is not acceptable but reforms may make it acceptable; or (c) concluding the only way to eliminate the risk of wrongful executions is to abolish the death penalty. States like Illinois and Massachusetts considered reforms but opted to do without the death penalty. Other states have balanced the risks and rejected the death penalty as well.[9] Ultimately it becomes a cost-benefit analysis that balances the necessity of having a death penalty with expenses and reforms. Studies have suggested reforms to various procedures, including interrogation requirements, lineup procedures, and limits on certain types of evidence. DNA exonerations highlight the problems, but DNA is not the complete solution.

What Do DNA Exonerations Teach Us About the Capital Punishment Process?

Finally, Garrett briefly notes that death penalty cases involve errors that go beyond guilt. This important DNA lesson is worth more discussion. Because DNA exonerations show that jurors make mistakes on the question of guilt, then jurors likely make mistakes on more complicated issues like difficult capital sentencing issues.

Since the beginning of the modern death penalty era in 1972 when the Supreme Court struck down the existing death penalty statutes, the Court has tried to curtail arbitrariness when jurors decide whether a guilty defendant should be sentenced to death or life in prison.[10] Legislatures have also struggled to write fair death penalty statutes to guide sentencing juries.

Generally, in capital sentencing proceedings, a jury considers aggravating evidence for death against mitigating evidence in favor of life in prison. Capital sentencing, unlike a question of guilt, requires jurors to bring their own values to the question of whether another person should live in prison or be executed by the state. In making this calculation, jurors not only measure the heinousness of the murder, but in a complex calculation they also evaluate mitigating factors like a defendant’s mental illness.

So if DNA reveals that jurors sometimes get wrong the most objective issue regarding a defendant’s guilt under a high burden of proof, they will sometimes be wrong in their decision about the death penalty. Just as death penalty advocates may argue that there are few true exonerations of capital defendants, they may still argue that jurors usually get it right when they evaluate whether a defendant should live or die. By contrast, death penalty opponents may point to a number of death row inmates who have changed in prison, arguing these individuals should be spared the death penalty.

Unlike cases with DNA innocence evidence, though, there are no objective standards to test the accuracy of a death sentence in most cases. But sometimes there is a sense that a sentence may be wrong. There was no debate that Wilbert Evans was guilty of shooting and killing a deputy sheriff in early 1984, and Virginia jurors confidently sentenced Evans to death after deciding he was a “future danger.” But not long after the jurors made that finding, Evans saved the lives of prison guards and personnel during a prison riot, putting himself between angry inmates and several hostages. Although the convicted murderer deserved harsh punishment, when the state executed him in the electric chair in 1990, his heroics in prison raised the question of whether the jury was right to sentence him to death instead of life in prison.[11]

DNA may help us discover some of the innocence cases, and it may help guide some needed reforms. But DNA evidence and other evidence that reveals errors in some cases cannot eliminate errors in all cases. Beyond the questions about guilt and innocence, such evidence also does not help eliminate sentencing arbitrariness. We can learn a lot from DNA, but it is only a beginning in assessing the way that governments use capital punishment.


[1] Edmund Pearson, “A Reporter at Large: Hauptmann and Circumstantial Evidence,” The New Yorker, 41 (March 9, 1935).

[2] Joshua Marquis, “The Myth of Innocence,” J. Crim. L. & Criminology 501, 509 (2005).

[3] See, e.g., Leon Friedman, “The Problem of Convicting Innocent Persons: How Often Does It Occur and How Can It Be Prevented”, 56 N.Y.L. Sch. L. Rev. 1053 (2012).

[4] Jay D. Aronson & Simon A. Cole, “Science and the Death Penalty: DNA, Innocence, and the Debate Over Capital Punishment in the United States,” 34 Law & Soc. Inquiry 603 (2009).

[5] See, e.g., Jeffrey Fagan, “Death and Deterrence Redux: Science, Law and Causal Reasoning on Capital Punishment,” 4 Ohio St. J. Crim. L. 255, 314-15 (2006); John J. Donohue and Justin Wolfers, “Uses and Abuses of Empirical Evidence in the Death Penalty Debate,” 58 Stan. L. Rev. 791, 842-45 (2005).

[6] See Michael L. Radelet and Traci L. Lacock, “Do Executions Lower Homicide Rates? The Views of Leading Criminologists,” 99 J. Crim. L. & Criminology 489, 501-05 (2009) (surveying seventy-six criminologists and finding that only 5.3% answered they believe the death penalty is a deterrent to murder).

[7] Gary L. Wells et al., “Witnesses to Crime: Social and Cognitive Factors Governing the Validity of People’s Reports,” in Psychology and Law: State of the Discipline 53, 57 (Ronald Roesch et al. eds., 1999).

[8] John L. Smith, et. al., “Prosecutors: Ky. Capital Punishment Unfair,” Lexington Herald-Leader (March 7, 2012).

[9] Sara Darehshori, Jeffrey L. Kirchmeier, Colleen Quinn Brady, and Evan Mandery, “Empire State Injustice: Based Upon a Decade of New Information, A Preliminary Evaluation of How New York’s Death Penalty System Fails to Meet Standards for Accuracy and Fairness,” 4 Cardozo Pub. Law, Policy & Ethics 85 (2006).

[10] See Furman v. Georgia, 408 U.S. 238 (1972); Gregg v. Georgia, 428 U.S. 153 (1976).

[11] Evans v. Muncy, 498 U.S. 927, 927, 930 (1990) (Marshall, J., dissenting); Stuart Taylor, “We Will Kill You Anyway,” The American Lawyer, Dec. 1990, 55–56.

Also from this issue

Lead Essay

  • Professor Brandon Garrett discusses the strengths and weaknesses of DNA as evidence. DNA offers a high degree of certainty in the cases where it is available, but in many cases, like that of Troy Davis, the DNA evidence just isn’t there. Individual exonerations are nonetheless suggestive of a wider pattern of wrongful convictions throughout the criminal justice system. It is difficult to say how large this pattern is, but DNA evidence has certainly made us aware of certain problems that existed prior to its use. Does this increase or decrease our faith in capital punishment? And where will public opinion settle? Garrett asks but does not fully answer these questions.

Response Essays

  • Joshua Marquis points out that prosecutors, not defense attorneys, first demanded the introduction of DNA testing. Defense attorneys fought it—until they realized that they could sometimes use the public’s confusion about the tests to produce doubt in jurors’ minds. Still, DNA secures many more convictions than exonerations. Taken as a whole, Marquis argues that DNA evidence shows our criminal justice system to have a vanishingly low rate of wrongful convictions. He readily grants that even a tiny number of wrongful convictions is too many, and of course we should not let the guilty go free. As a result, he recommends still more extensive DNA recordkeeping and testing.

  • Jeffrey Kirchmeier grapples with the thorny, inescapable problem of human error. He notes that DNA evidence has offered us a way to test other forms of evidence, such as eyewitness testimony and police lineups. But he moves quickly from these to still harder questions. If jurors can err on matters that admit of an objective answer, then what of the subjective questions they must also answer? The choice between capital punishment and life in prison is itself one of these subjective decisions, and it too may be flawed. Unfortunately, we have no way to test it.

  • George H. Smith reviews some of the key philosophical questions that have been raised about capital punishment. He discusses the views of several thinkers, including Jeremy Bentham, Nathaniel Branden, and Immanuel Kant. He also references Cesare Beccaria, who doubted the social utility of the death penalty. Even if DNA does offer certainty in the matter of guilt, Smith suggests that there may be independent and controlling reasons to reject capital punishment.