Skip to main content
Find a Lawyer

Prosecutorial Resistance to Exculpatory DNA Evidence
Why We Must Overcome It, And What Institutional Safeguards Will Help Us Do So


Thursday, Sep. 04, 2003

By far the most important development in the field of criminal justice over the last generation has been the advent of DNA analysis. The most dramatic result of DNA testing has been the exoneration of literally hundreds of inmates who were wrongly convicted of serious crimes and sentenced to lengthy prison terms and even death.

Meanwhile, and equally importantly, DNA testing has, for the first time ever, given us a tool for assessing the accuracy of our adversarial system for determining guilt or innocence. We now know to a scientific certainty that police, prosecutors, and juries make catastrophic mistakes - especially when they overly rely on such inherently problematic evidence as jailhouse informants, hair samples, and even eyewitness testimony, which turns out to be surprisingly unreliable.

The legal system is still adjusting to the truth-revealing power of DNA analysis. Of course, prosecutors have sought to use DNA evidence to prove their cases (often successfully - though not, most famously, in the O.J. Simpson case). And of course, defense attorneys turned the tables by using DNA evidence to prove innocence, sometimes many years after a defendant's conviction. But the ramifications of DNA evidence go far beyond its use at current and future trials. DNA also sheds light on the past.

Sometimes, though, the light it sheds has proved unwelcome. In the chess game of our adversarial system, prosecutors are now resisting the re-opening of cases based on DNA evidence. And even if cases are re-opened, they are fighting in court to preserve even those convictions on which DNA testing has cast extremely serious doubt.

Prosecutors face institutional pressure to win victories, and then preserve what they have won. And of course, like all of us, they share the human impulse to resist admitting error - especially when the admission could hurt their careers. They also share the need we all have for closure - to believe that, at some point, what's over is over and done with - and DNA evidence issues are the quintessential example of reopening the past, and sometimes even the distant past. As a result, we cannot trust individual prosecutors always to do the right thing when DNA puts their hard-won convictions in doubt.

Instead, prosecutor's offices must voluntarily put in place institutional safeguards to ensure that the great advances in criminal justice made possible by DNA evidence are realized to their fullest. And if they refused, legislation should be enacted to force them to do so. A prosecutor's stake in a particular victory should not be able to blind the eyes of justice, so that an innocent person wrongly remains in jail.

In Recent Cases, Prosecutors Have Refused to Accept DNA-Based Exoneration

In recent days, the New York Times has reported a spate of cases in which new DNA testing refuted the main evidence on which convictions had been based. Yet in each case, prosecutors nevertheless steadfastly refused to accept that they had prosecuted and convicted the wrong person.

In some of these cases, the DNA evidence points powerfully towards the conclusion that the conviction was wrongful. In one rape case, semen recovered from the victim was matched to the blood type of the defendant, Richard McKinley. But DNA tests have now shown that in fact, the semen did not come from McKinley.

In another rape case, the only physical evidence linking the defendant, Wilton Dedge, to the crime was a pair of light brown hairs. Through expert testimony, the prosecutor tied the hairs the defendant. Thanks to DNA testing, we now know the hairs did not belong to Dedge.

Yet prosecutors in both cases refuse to admit that the DNA tests are sufficient to show the defendants' innocence. As a result, both defendants are still serving life sentences. According to the prosecutors, even assuming the accuracy of the DNA tests, the remaining evidence still supports the defendants' convictions.

As a factual matter, though, the prosecutors' claims are suspect. Take the Dedge case. Excluding the hairs, the remaining evidence was the victim's physical description (which Dedge did not even match); the testimony of a jailhouse informant that Dedge had confessed to him; and the testimony of an expert who claimed Dedge had been picked out by a dog in a "scent line up."

Surely, this case never would have been prosecuted but for the now-discredited hair match. And with good reason.

Why Prosecutors' Offices Need to Adopt an Institutional - Not Individual - Solution

Situations like this raise a serious institutional problem for every prosecutor's office in the country. Trial prosecutors, who have invested themselves in cases, will rarely if ever have the necessary perspective to evaluate convictions being challenged on the basis of new DNA evidence.

Inevitably, too many line prosecutors will view DNA evidence of innocence as an attack on their judgment and abilities, as well as those of their colleagues. When DNA evidence casts doubt on a conviction, it may also be seen as casting doubt on the thoroughness of the police investigation, and on the judgment of the entire prosecution team in evaluating a case. Of course, that doubt may be undeserved: Police and prosecutors can be scrupulous, yet still be wrong. But the doubt is cast, and felt, nonetheless - and police and prosecutors, both good and bad, may resent it.

At a personal level, no prosecutor - good, bad, or indifferent - is going to be naturally inclined to accept the idea of having obtained a wrongful conviction. For the best prosecutors, such a concession means accepting the ultimate professional failure of disserving the paramount mission of protecting the public and achieving justice. And more self-serving prosecutors are likely to be consumed by the career implications of admitting such a giant screw-up.

In many cases, line prosecutors will also face substantial pressures from crime victims and their families not to admit error. The victims and families want closure, too. As a theoretical matter, one might think that victims and their families would want to know the truth, whatever it may be, and that their primary interest would be in finding the real criminal. But in practice, that is not always true.

According to those involved in the process, in many cases, the victims and their families are just too invested in the result obtained at trial to open their minds to the possibility of mistake. After a terrible ordeal, they have obtained a measure of peace and vindication that is simply too valuable for them to easily let go.

As a result, the victims or their representatives - who often have developed deep bonds with the prosecutors - reinforce the reluctance of prosecutors to reopen cases. The prospect that the convicted defendant is innocent, or very likely so, often turns out not to be welcome news to anyone. Only the innocent defendant himself - and possibly his defense counsel, though defense counsel, too, may fear that their skills have been put in doubt - is eager to see DNA evidence reopen the case.

There is thus a desperate need for District Attorneys and U.S. Attorneys to establish independent, separate units or committees within their offices to evaluate claims of innocence based on DNA evidence. The original prosecutor, while he or she will have input, is far too close to the issue to decide what the office's position on reopening a case - or even agreeing that a conviction should be vacated - in light of DNA evidence.

There will be cases where DNA evidence should not be deemed sufficient to unsettle a conviction - for the other evidence against the defendant may, standing alone, be overwhelming. But there will also be cases, probably many more, where the wrongly convicted person must be set free as soon as possible, because the DNA evidence either was the linchpin of the case against him, or actually points to another person's guilt.

Deciding which cases fit in which category is a job for experienced prosecutors with no vested interest in the original prosecution - not for the prosecutor who obtained the conviction (and congratulations in the office for it) in the first place.

Many prosecutors offices use this same system of independent peer review when deciding which potential cases should actually lead to the filing of criminal charges, and which - while perhaps technically violations - are too hard to prove, or too minor to use resources upon. After developing a case, line prosecutors must obtain the approval of an "indictment committee." This committee is a group of prosecutors with no interest in the case under review, who are called upon to decide whether the evidence developed is sufficient to meet the standard for actually charging a crime.

The "DNA committee" I am proposing would work much the same way. If DNA testing discredits evidence used to obtain a conviction, then the committee would evaluate the quantity and quality of the untainted evidence to determine whether the office should admit error - or at least support a court's reopening the case, or agree to a re-trial.

In sum, DNA evidence provides a unique window into the truth of guilt or innocence. And every effort must be made to keep that window free from the dust and dirt of conflicts of interest, especially prosecutors' interests in keeping the convictions they have won pristine.

Edward Lazarus writes about, practices, and teaches law in Los Angeles. A former federal prosecutor, he is the author of two books - most recently, Closed Chambers: The Rise, Fall, and Future of the Modern Supreme Court.

Was this helpful?

Copied to clipboard