How Often Do Wrongful Convictions Occur?

Wrongful convictions, a staple of Hollywood movies, crime shows, and books
alike, aren’t quite as common in the real world. Until very recently,
the number of wrongful convictions was assumed to be 0.027%. It was such
a widely noted statistic that the late U.S. Supreme Court Justice Antonin
Scalia included it in a concurring opinion in 2006.

That number comes from a
NY Times op-ed piece, written by Clatsop County, Oregon District Attorney Joshua Marquis. In
it, he cites a study led by University of Michigan law professor Samuel
Gross that found 340 inmates, almost all of whom were convicted in rape
and murder cases, who were exonerated between 1989 and 2003. Marquis compared
those 340 cases to the approximately 15 million felony convictions over
that 15 year stretch. “That would make the error rate .027 percent
– or, to put it another way, a success rate of 99.973 percent,” he said.

In 2014, Gross published a
new study, this time refining his search parameters just to death row inmates. He
stated that the lack of a method to determine the accuracy of criminal
convictions results in very few discoveries of false convictions, and
those discoveries that lead to exonerations are disproportionately concentrated
among inmates on death row.

“We use survival analysis to model this effect, and estimate that
if all death-sentenced defendants remained under sentence of death indefinitely,
at least 4.1% would be exonerated. We conclude that this is a conservative
estimate of the proportion of false conviction among death sentences in
the United States.”

Gross and his research team argued that, while their study only focused
on less than 0.1% of prison sentences, these cases received an increased
level of scrutiny due to the severity of the punishment. Given the amount
of resources spent on cases of capital punishment, the researchers reason
that it’s likely that a falsely convicted inmate on death row will
be exonerated. They believe that their calculations, when applied to all
felony convictions – the vast majority of which receive minimal scrutiny
– gives a realistic estimate of false conviction rates.

Compounding this issue is the fact that less than half of the people who
are found guilty of murder end up on death row; rather, they end up serving
life in prison. Given the results from Gross’ study, it’s
reasonable to assume that there are at least several hundred innocent
people serving life in prison. When you factor in a report released by
the American Civil Liberties Union that found black people were 3.7 times
more likely to be arrested than white people for marijuana possession
despite comparable usage rates, that 4.1% found in the study begins to
look like it might be a low estimate

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