Science and law has revealed many hundreds even thousands of wrongfully convicted criminal defendants over the years, but the big questions remain:  how many other innocent defendants are there, who are they, and how many innocent people in prison have died, or been wrongfully executed?  New research finds that almost 4% of U.S. capital punishment sentences are wrongful convictions, double the previous estimation.  The U.S. may be putting to death more innocent people than previously thought.

According to a new statistical analysis, the rate of wrongful death sentences is much higher than previously estimated.  It has long been known that capital cases have more pitfalls than other cases, but the authors of the study say their “conservative estimate” is approximately twice the number of known exonerations (which sits at about 1.6%) or 4.1% of the death row population.

This could mean that 120 people currently on death row are actually innocent, while additional scores of innocent people are serving life in prison after their death sentences were reduced on technical legal errors.  The study found that 1 in every 25 death row inmates are likely innocent and that of the more than 1,320 people executed since 1977 some were innocent.

“False convictions…are extremely difficult to detect…” said law professor Samuel Gross of the University of Michigan and Barbara O’Brien of Michigan State in the Proceedings of the National Academy of Sciences, the prestigious journal the study was published in, “As a result, the great majority of innocent defendants [are] undetected.  The rate of such errors is…a dark figure.”

By applying statistical models derived from medicine and mortality studies, the authors assert that “it [is] possible to use data on death row exonerations to estimate the overall rate of false conviction among death sentences.”  Two experts in statistics, Chen Hu of the American College of Radiology and Edward Kennedy of the University of Pennsylvania crunched the numbers.

“This study provides the first rigorous estimate of the rate of conviction of innocent criminal defendants…” said Bruce Levin, a Columbia University professor who is a leading authority on statistics and the law.

The study supports the rising misgivings about the practice of capital punishment.  A recent Pew Research Poll found that 37% of U.S. adults oppose the death penalty.  Since 2007, 6 states have abolished capital punishment in favor of life in prison without parole.  A recent attempt by New Hampshire to repeal their death penalty fell short as their legislature has deadlocked.

To calculate the rate of wrongful convictions in capital cases, the study applied an analytical formula to a set of data comprising of all prisoners sentenced to death between 1976 and 2004.  “Survival analysis” was the method used in the study.  In medicine, that is the method used to estimate the likelihood that a patient will survive a certain disease or injury.  The researchers turned the fatal event that they were looking for from death to exoneration.  Their overall “infected” population was prisoners who received death sentences and they plugged in various variables to find the number of patients likely to “pass” into freedom.  It gets tricky though.  The likelihood of an innocent prisoner being exonerated depends upon whether the government wants to kill them and is actively trying to.

As the authors observed:  “Death sentences represent less than 1/10th of 1% of prison sentences in the U.S., but they accounted for about 12% of known exonerations…”

This “extraordinary rate” for prisoners facing execution is evidence of the reality that “far more attention and resources are devoted to death penalty cases than to other criminal prosecutions, before and after conviction.”

As other studies have found, the more resources and time spent on a case, the more likely the media, the public, and authorities are to suffer from tunnel vision.  On the flip side, innocence advocates focus more on death penalty cases because the person’s life is in immediate danger and executions cannot be fixed.  But a large portion of death row inmates (1/3rd) have their sentences reduced to life in prison.  Typically, attention drastically drys up as the death row inmates are in more urgent need.  This also affects the cases of those who die from suicide or natural causes while on death row.  The authors believe the true rate of innocent defendants on death row would have to include these prisoners, who have left the sight of the appeals process without having their potential innocence vetted.

“The high rate of exoneration among death-sentenced defendants appears to be driven by the threat of execution,” says the study, “But most death-sentenced defendants are removed from death row and re-sentenced to life imprisonment, after which the likelihood of exoneration drops sharply.”

The study also found that though the number of innocent people actually put to death is “comparatively low” to innocent people serving time in prison, “the criminal justice system goes to far greater lengths to avoid executing innocent defendants than to preventing them from remaining in prison indefinitely.”

The study also notes that there is no shortage of lawyers and judges who assert that the number of false convictions is “negligible”, some even call it “collateral damage”, including Supreme Court Justice Antonin Scalia, who recently said that it is lawful to sentence an innocent person to prison if all constitutional protections are enforced and they are given a fair trial.

“Our procedure has always been haunted by the ghost of the innocent…,” said Judge Learned Hand in 1923.

Justice Scalia wrote in 2007 that the error rate for the justice system is “0.027 percent”.  The study noted that Scalia’s numbers were “comforting”, but not accurate in the least.  The study said that reality is far less warm and fuzzy.

“Most innocent defendants…have not been exonerated, and many…probably never will be.”

The study indicates that about 144 death-sentenced inmates have been exonerated since 1973, but that number should be at least 340.  The analysis did not include data after 2004.  The researchers doubt that DNA exonerations are having much of an impact, given most cases do not include DNA evidence and while they are the most publicized, they are the minority of exonerations.

You can read the full study here:  Rate of False Conviction of Criminal Defendants Who Are Sentenced to Death (Proceedings of the National Academy of Sciences)

  1. Lon Spector says:

    Lets just banish TDP. That way won’t have to worry about who deserves it and
    who doesn’t.


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