DPI’s ​“What to Know” series exam­ines cap­i­tal pun­ish­ment from mul­ti­ple angles, one top­ic at a time. Each install­ment pro­vides essen­tial facts and data on spe­cif­ic aspects of the death penalty.

Why it mat­ters: The death penal­ty is an irre­versible pun­ish­ment, and the United States has con­vict­ed, con­demned, and in some cas­es exe­cut­ed peo­ple despite cred­i­ble evi­dence of their innocence.

  • 202 peo­ple have been exon­er­at­ed from death row since 1973, across 30 states.
  • A peer-reviewed study esti­mat­ed that at least 4.1% of peo­ple sen­tenced to death were wrong­ful­ly con­vict­ed, more than twice the share who have been formally cleared.
  • Death row exonerees spent an aver­age of 13 years under a death sen­tence before release. That wait is grow­ing, reach­ing a record 38.7‑year aver­age for those exon­er­at­ed in 2024.
  • 65% of exonerees are peo­ple of col­or. More than half are Black.

Key Facts

  • The doc­u­ment­ed count is a floor, not a ceil­ing. The 202 known exon­er­a­tions under­state the prob­lem because prov­ing inno­cence after con­vic­tion is rare and slow. A 2014 study in the Proceedings of the National Academy of Sciences used sur­vival analy­sis, a method bor­rowed from med­ical research, to esti­mate the true rate of wrong­ful con­vic­tion. It found that at least 4.1% of peo­ple sen­tenced to death between 1973 and 2004 were like­ly wrong­ly con­vict­ed, a rate the authors called con­ser­v­a­tive. Only 1.6% were actu­al­ly exon­er­at­ed. The gap exists because death row draws intense legal scruti­ny, but when a pris­on­er is resen­tenced to life, that scruti­ny col­laps­es, and the chance of exon­er­a­tion falls by close to 90%. 

  • Wrongful con­vic­tions are caused by the state, not by bad luck. Official mis­con­duct by police, pros­e­cu­tors, or oth­er gov­ern­ment offi­cials appears in 70.5% of death row exon­er­a­tions. False accu­sa­tions or per­jured tes­ti­mo­ny appear in 65%. Discredited foren­sic sci­ence, coerced con­fes­sions, mis­tak­en eye­wit­ness­es, and inef­fec­tive rep­re­sen­ta­tion recur across the cases. 
  • The bur­den falls along racial lines. Among Black exonerees who had been sen­tenced to death, 87% were vic­tims of offi­cial mis­con­duct, com­pared to 67% of white death row exonerees. Black exonerees also wait longer for release than white exonerees con­vict­ed of sim­i­lar crimes. Race shapes both who is wrong­ly con­demned and how long the error stands before it is cor­rect­ed. Glynn Simmons spent more than 48 years incar­cer­at­ed before Oklahoma cleared him in 2023, the longest wrong­ful impris­on­ment record­ed in the United States.
     
  • Innocence some­times sur­faces by luck. DNA evi­dence exists in only about 17% of death row exon­er­a­tions. The rest depend on a wit­ness recan­ta­tion, a con­fes­sion by the real killer, or secur­ing the assis­tance of a defense lawyer will­ing to spend years reopen­ing a closed file. Anthony Porter nar­row­ly avoid­ed exe­cu­tion and was only exon­er­at­ed from Illinois’ death row because jour­nal­ism stu­dents uncov­ered new evi­dence in his case. 

  • Innocence is not a guar­an­teed bar to exe­cu­tion. In Herrera v. Collins (1993), the Supreme Court held that new evi­dence of inno­cence, on its own, does not enti­tle a pris­on­er to fed­er­al relief with­out first demon­strat­ing a sep­a­rate con­sti­tu­tion­al vio­la­tion at tri­al. The Court assumed with­out decid­ing that a tru­ly per­sua­sive inno­cence claim might block an exe­cu­tion, and it has nev­er resolved whether exe­cut­ing an inno­cent per­son vio­lates the Constitution. Federal law nar­rows the path fur­ther. The Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA) impos­es a one-year fil­ing dead­line, requires def­er­ence to state-court rul­ings, and lim­its most defen­dants to a sin­gle review of their case, which keeps many inno­cence claims out of fed­er­al court regard­less of the evi­dence. The Court point­ed instead to exec­u­tive clemen­cy as the safe­ty net, but gov­er­nors and boards grant it rarely.

Relevant Cases

1. Robert Roberson

Robert Roberson has been on Texas death row since 2003 for the death of his two-year-old daugh­ter, Nikki Curtis. His con­vic­tion rest­ed on a Shaken Baby Syndrome (SBS) diag­no­sis that defense experts now dis­pute, point­ing instead to undi­ag­nosed pneu­mo­nia that turned sep­tic, wors­ened by med­ica­tions lat­er judged unsafe for young chil­dren. The lead detec­tive who inves­ti­gat­ed the case, Brian Wharton, now believes Mr. Roberson is inno­cent. Texas set an exe­cu­tion date of October 16, 2025. Days before, the Court of Criminal Appeals issued an emer­gency stay and returned the case to the tri­al court, after the same court had recent­ly vacat­ed anoth­er con­vic­tion built on the same SBS the­o­ry. If exe­cut­ed, Mr. Roberson would be the first per­son in the coun­try put to death based on that now-debunked diag­no­sis. The Texas Attorney General’s office main­tains the death was a homi­cide. As of spring 2026, a judge is weigh­ing whether Mr. Roberson should receive a new tri­al under the state’s junk sci­ence law. 
 

2. Marcellus Williams

Missouri exe­cut­ed Marcellus Williams on September 24, 2024, for the 1998 mur­der of Felicia Gayle. No phys­i­cal evi­dence tied him to the crime. DNA on the mur­der weapon did not match him, and the con­vic­tion rest­ed on two wit­ness­es who stood to gain from tes­ti­fy­ing. The local pros­e­cu­tor moved to vacate the con­vic­tion. The vic­tim’s fam­i­ly sup­port­ed a life sen­tence instead of death. The gov­er­nor, the Missouri Supreme Court, and the U.S. Supreme Court each declined to inter­vene. Clemency, the safe­ty net the Supreme Court named in Herrera, was sought and refused. DPI now lists him among those exe­cut­ed despite cred­i­ble evi­dence of inno­cence.

Global Perspective

The risk that exon­er­a­tion comes too late is the cen­tral prob­lem with a pun­ish­ment that is final and irre­versible. DPI pro­files 21 peo­ple exe­cut­ed in the mod­ern era despite seri­ous doubts about guilt, among them Cameron Todd Willingham, con­vict­ed on arson sci­ence that fire experts lat­er reject­ed, and Troy Davis, exe­cut­ed in 2011 after most of the wit­ness­es against him recant­ed. Once a per­son has died, courts rarely reopen the ques­tion of a person’s guilt or inno­cence, so the true num­ber of wrong­ful exe­cu­tions stays unknown.

The same risk dri­ves the inter­na­tion­al con­sen­sus. Amnesty International records hun­dreds of U.S. exon­er­a­tions and notes that no legal sys­tem elim­i­nates the dan­ger of exe­cut­ing an inno­cent per­son. The United Kingdom posthu­mous­ly quashed the con­vic­tions of Derek Bentley and Mahmood Hussein Mattan. China exon­er­at­ed Nie Shubin and a teenag­er known as Huugjilt years after their exe­cu­tions, once the real killers were iden­ti­fied. In December 2024, 130 United Nations mem­ber states vot­ed for a glob­al mora­to­ri­um on the death penal­ty, the high­est lev­el of sup­port yet recorded.

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