More than four percent of defendants sentenced to death in the United States are innocent, according to a new study published in the Proceedings of the National Academy of Sciences.
Of the 7,482 defendants sentenced to death between 1973 and 2004, 117 (1.6 percent) were exonerated, according to the study.
But many defendants are eventually resentenced to life in prison, and once the threat of capital punishment is removed, fewer resources are typically poured into examining their cases.
The study's authors — who include National Registry of Exonerations editor Samuel Gross — used survival analysis, a statistics tool commonly used in medicine, to produce an estimate of the number of inmates initially sentenced to death who could be exonerated.
The authors note in their that they consider the estimate, 4.1 percent, to be conservative.
“[N]o process of removing potentially innocent defendants from the execution queue can be foolproof. With an error rate at trial over 4%, it is all but certain that several of the 1,320 defendants executed since 1977 were innocent,” the authors wrote.
Read the full study HERE.