National Geographic

How Many People Are Wrongly Convicted? Researchers Do the Math.

Is there a more tragic story than an innocent person going to prison? Tragic, and powerful. That’s why The Shawshank Redemption is one of the most beloved movies of our time. And why we’ve all heard of this quote from an esoteric 18th-century English guy, William Blackstone: “It is better that ten guilty persons escape than that one innocent suffer.” And why real-life stories of the exonerated always make headlines. Here’s the first line of a Washington Post story about Glenn Ford, who was exonerated last month:

“My sons, when I left, was babies,” Louisiana’s longest-serving death row inmate told reporters after his release late Tuesday. “Now they’re grown men with babies.”

It hits you in the gut. You first think about this particular person, this man who lost his family, who spent decades in some awful cell believing he was going to be electrocuted. And then you think that other frightening thought, the bugaboo lurking behind all exoneration stories: How many other Glenn Fords are still behind bars? How many will die there? Just how often does our venerated justice system fail?

Rarely, at least according to U.S. Supreme Court Justice Antonin Scalia. In a 2006 opinion he cited an approximate error rate of 0.027 percent, based on back-of-the-envelope calculations by an Oregon district attorney in a fiery op-ed for the New York Times. The op-ed was in response to a report by Samuel Gross, a law professor at the University of Michigan, cataloguing 340 exonerations between 1989 and 2003. “Let’s give the professor the benefit of the doubt,” the op-ed read. “Let’s assume that he understated the number of innocents by roughly a factor of 10, that instead of 340 there were 4,000 people in prison who weren’t involved in the crime in any way. During that same 15 years, there were more than 15 million felony convictions across the country. That would make the error rate .027 percent — or, to put it another way, a success rate of 99.973 percent.”

But that claim, Gross writes in today’s issue of the Proceedings of the National Academy of Sciences, “is silly.” Here’s the problem with its logic. The known exonerations were almost all murder and rape cases, which get much more post-conviction attention, whereas the total number of felonies also includes burglary, car theft, tax fraud, and drug possession. Some 95 percent of felony convictions are the result of plea bargains, with no formal evidence ever presented, and most never bother with an appeal.

There’s a more rigorous way to crunch the numbers, according to Gross’s new study. And that approach leads to a false conviction rate that was high enough to make me gasp — 4.1 percent.

To be more precise: Gross and his colleagues calculated a 4.1 percent error rate among people who are sentenced to death. This is a small subset (less than 0.1 percent) of the total number of prison sentences but, because of the stakes, these cases are scrutinized far more than most. For capital cases, Gross writes, “everyone from defense lawyers to innocence projects to governors and state and federal judges is likely to be particularly careful to avoid the execution of innocent defendants.”

Because of all of the resources spent on capital cases, the researchers reason, it’s likely that many (and perhaps a majority) of innocent defendants on death row will ultimately be exonerated. Calculating this rate would then give an approximate, albeit low estimate of the real false conviction rate.

Even with this small subset, though, getting a reasonable estimate is tricky, for two reasons. One is that the exoneration process takes time. To date 143 people on death row have been exonerated, and their time spent on death row ranged from 1 to 33 years, with an average of 10. That means there are some number of innocent people on death row today who have not yet been exonerated but will be in the future.

The other issue is that some number of innocent people on death row will have their sentence reduced to life in prison but will never be freed. (Why? Because once they’re off death row, their case is no longer under such intense scrutiny and exoneration is unlikely.)

Gross and his colleagues collected data on the 7,482 people who were sentenced to death between 1973 — the first year of modern death-penalty laws — and 2004. Of these, 117 were exonerated, or 1.6 percent. But among these, 107 were exonerated while they were still on death row, whereas only 10 were exonerated after their sentence had been reduced to life in prison.

This leads to a bizarre situation. If you’re on death row and your sentence is reduced to life in prison, you’re suddenly much less likely to be exonerated than someone who stays on death row.

To account for the X number of innocent defendants who were lost to life in prison, Gross’s team borrowed a statistical approach from medical research called “survival analysis.” Researchers typically track how long it takes a group of people with some disease, say diabetes, to achieve a certain outcome, such as death. Survival curves for diabetics on some new drug treatment, say, can then be compared with those on no treatment.

In this study, the “disease” is being on death row, the “outcome” is exoneration, and the “treatment” is being moved to life in prison. (Just as a medical treatment is likely to lower a diabetic’s risk of death, being moved to life in prison lowers the risk of exoneration.) Using this mathematical approach*, the researchers were able to calculate the cumulative risk of exoneration for the “untreated” population — that is, people who were never removed from death row. Because these cases get the most intense scrutiny, the researchers say, this is the closest we can get to the true rate of death-row false convictions. And that rate is 4.1 percent.

All of this assumes that the rate of innocent people being sentenced to death hasn’t changed over the past four decades. The authors say there’s no specific evidence to support a change, though it’s true that we’re sending far fewer people to death row than we used to. I thought that improvements in DNA technology might have lowered our error rate, but the researchers don’t think it makes much of a dent. Just 18 of the 142 exonerations since 1973 were thanks to DNA testing.

So then the next terrifying question is, geeze, how many innocent people have actually been executed?

Fortunately it’s probably not many. Innocent defendants are far more likley to have their sentenced changed to life in prison than to be executed. Still, with an error rate of 4 percent, the researchers write, “it is all but certain that several of the 1,320 defendants executed since 1977 were innocent.”

It’s impossible to say whether this 4.1 percent false conviction rate applies to defendants who never went to death row. But I’ll leave you with one last depressing thought. Of all of the people found guilty of capital murder, less than half actually get a death-penalty sentence. And when juries are determining whether to send a defendant to death row or to life in prison, surveys show that they tend to choose life sentences when they have “residual doubt” about the defendant’s guilt.

That means, then, that the rate of innocent defendants serving life in prison is higher than those on death row. “They are sentenced,” the authors write, “and then forgotten.”

*If you want to know about the particular equations involved in the survival analysis, check out Gross’s paper or the Wikipedia article on the method.

Update, 4:51pm: The text has been amended to correct a statistic about the number of death sentences. They make up 0.1 percent of the total number of prison sentences, not of the criminal population at large. 

There are 9 Comments. Add Yours.

  1. Robert LeChef
    April 28, 2014

    It’s certainly tragic when an innocent person goes to prison, much worse when facing the death penalty. And perhaps there’s something to be done to improve the odds of the innocent. Movies like “Shawshank” are great tragedies, but to understand interpret all movies as having a social subtext is simply asinine and tendentious. One should watch such movies for the art of them, much like Greek tragedies were watched and for their cathartic value. Let’s not overstate the problem either. Indeed, we’ve grown rather perverse in the previous century when it comes to how we treat the victim and the perpetrator. The truth is that by far most people in prison are there because they’re guilty and most people on death row by far are there because they committed a heinous crime. And yet we seem to focus so much of our energy on the “rights of the criminals” and not the rights of the victims. We exchange compassion for the victim for false compassion for the criminal. This is a sick state of affairs. That we obsess over prison conditions is to me repulsive, a denial of the severity of the crime, a spitting in the face of the victim and their family. I know people working in today’s modern prisons. It is laughable to claim that the conditions in these prisons are bad. They are not. If they are overcrowded, it is because we fill them with 20 year olds found in possession of a little weed for personal use or black kids caught stealing a Snickers at a 7-11 instead of the real criminals, the drug dealers, sex offenders, murderers (life in prison can mean years nowadays; we have no concept of justice anymore), and high rolling embezzlers in government and corporation. Prisoners are too comfortable and have too much say in prisons. They are afforded luxuries they should not be receiving and routinely manipulate the softness of the system to their advantage. Prison is a place to pay, it should be uncomfortable, it should be hard and difficult. Indeed, prisoners should be put to hard labor to pay for their time in prison because the amount of money we’re spending on prisoners per annum is sickening, especially when there are so many good people who could benefit from that money.

    Sure, a wrongful conviction is a tragedy and we should do all that we reasonably can to prevent them and make use of capital punishment as carefully and as justly as possible, but we have bigger problems and pathologies to face than something which is to a large degree an anomaly or merely the unfortunate reality of justice systems i.e. that they are never perfect and never will be.

    • Virginia Hughes
      April 29, 2014

      Thanks for reading. To me, 4.1 percent is not an “anomaly.”

  2. Alex
    April 28, 2014

    I posit that a significant problem behind high conviction rates of the innocent is that there is no feedback system discouraging either prosecutors or the Justice Department in general from convicting the innocent, yet there are career rewards for being a successful prosecutor who must attempt to convict even the innocent, in some cases even going to great lengths to bend the truth and the law to do so. A man found to be innocent after ten years in prison gets basically nothing from the government in recompense, and so the government has no financial reason to avoid convicting him out of hand, and several reasons to convict that have nothing to do with whether he might be guilty, and are significantly more profitable since the government gets to keep all the fines and seized property – though somehow many of these seizures can happen long before trial.

    I’d like to propose that the government *should* be held accountable for the such misdeeds, and recompense the released in terms of salary lost, plus a base remuneration. However, I fear even this would have two horrible side effects: First the government would become even more determine to bury such cases than they are now, intentionally blocking reversals. And second, I can imagine people attempting to game the system by encouraging their own conviction in the face of their own innocence, to reap a financial reward later. Both of these fly in the face of how a justice system should work.

    I think only creating a separate department of government, with a separate budget, with the specific objective of reversing convictions, would have a worthwhile chance of improving the scenario.

    I agree that the government heavily abuses plea bargains. The system forces someone accused of crimes they didn’t commit to figure the odds of a plea bargain yielding (say) six months of probation versus a plea of innocence possibly yielding years of jail time. The federal courts assume that if someone who pled innocent is found guilty, that the must have known they were guilty, and therefore either lied or failed to repent, and applies the maximum sentence when possible. This sentencing paradigm doesn’t take into account that a person who was innocent would resist out of a sense of justice despite the horrible way the Justice Department likes to bend the game, and instead punishes these innocents more harshly then the admitted wrongdoers – and more harshly than the innocents who falsely pled to doing wrong, in an attempt to put at risk fewer years of their lives and time with those they love. Prosecutors know how to leverage this fear, and plea bargains often include surrendering property legally held along with that allegedly held in violation, making for a tidy profit for the government. Prosecutors will even ask the defendent to propose a crime to use to plea bargain, but at the federal level there are surprisingly few misdemeanors to use for this purpose, making it hard to find anything for a non-felony level plea bargain.

    And even at the sentencing, the results are bizarre, with judges grinding personal axes, accusing the one being sentenced of other crimes, conflating testimony between cases, scaling the sentence based on truly odd questions about the sentencee’s past, seemingly on a whim, and always fully believing the testimony of any other person sentenced despite the fact the accusation itself is often bought with a plea bargain – and even the court records are inaccurate, with meanings inverted, answers tied to the wrong questions (by omitted material between), etc. In many respects, a federal judge can run a court like a teacher can a kindergarten, making snap judgements based on personal biases, on incorrect, invariably negative conjectures about what the accused’s motives were, with credit given to whoever accused first, and like the kindergarten teacher, with no oversight and no culpabilty for being wrong, since no one of authority would ever believe the just-sentenced over the voice of another in authority.

    The Justice Department doesn’t care if you’re innocent; what they care about is are you *convictable*. And therein lies the problem.

  3. Owen
    April 29, 2014

    The only query I have is the difference between exonerated and innocent. For example, Ruben Carter’s conviction was overturned, it is not correct to state he was innocent as a matter of fact.

    There will be false positives as well as false negatives in exoneration stats.

  4. Andrew Benjamin Esq.
    April 29, 2014

    “Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgement. For even the very wise cannot see all ends.”

    There can be no such thing as judicious use of capital punishment, since it is, by it’s nature, irreversible. We are precluded by nature from either infallibility or restoring life to those who deserve it and therefore we may never legitimately deal out death in judgement, at least not after the fact, i.e., self defense in the moment.

    That’s the end of that discussion. Any other ramblings are merely the ravings of the Socratically flawed..

  5. Jud
    April 30, 2014

    Murder “in cold blood” is thought, by our moral standards, to be more heinous than murder in the passion of the moment.

    What does that say about the morality of a system that asks the state to seek, and jurors to impose, a sentence of death, calmly and dispassionately?

  6. Michael Buckley
    May 3, 2014

    @Robert LeChef
    You say that life in prison should be hard and difficult. That depends on what you want the prison to do. Is the main goal to punish, or to rehabilitate the person so they can come out a good law abiding citizen.

    @Andrew Benjamin Esq.
    Nice quote. I should really read that book again.

  7. dennis
    May 3, 2014

    If we send one innocent person to prison we should consider that a tragedy. That’s why it says innocent until proven guilty. Many times jury’s go with their gut rather than cold hard facts. Worse yet many cases are tried in the media before it ever hits a court room.

  8. chaunta shannon
    May 14, 2014

    My 23 year old son is currently being a poster child for the judicial systems policial gain for a very racial small town pascagoula Missisippi. I would like for my son to get a far shake but I don’t know who, what, where a criminal attorney can be contacted. I would like to head the problem of getting on more wrongly convicted human being. If any one can advice please help me and my family.

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