Autopsy Points to Reason Behind Byron Black’s Painful Execution in Tennessee

Byron Black was exe­cut­ed in Tennessee by lethal injec­tion on August 5, 2025. During his exe­cu­tion, Mr. Black unex­pect­ed­ly and repeat­ed­ly groaned over the course of sev­er­al min­utes and audi­bly told his spir­i­tu­al advi­sor that he was in pain. An autop­sy released September 10, 2025, pro­vides some expla­na­tion. It found evi­dence of ​“pul­monary con­ges­tion and ede­ma”– defined as an abnor­mal buildup of flu­id in the lungs which can pro­duce sen­sa­tions of ​“doom, pan­ic, drown­ing, and asphyx­i­a­tion” accord­ing to Dr. Mark Edgar, a pathol­o­gist and autop­sy direc­tor at the Mayo Clinic in Florida until his death ear­li­er this year. 

Mr. Black’s suf­fer­ing was not unprece­dent­ed. In 2016, Dr. Edgar and Dr. Joel Zivot, then both at the Mayo Clinic, began exam­in­ing autop­sy reports of exe­cut­ed pris­on­ers and noticed that many of the pris­on­ers’ lungs were twice as heavy as they should have been. After gath­er­ing more records, they found pul­monary ede­ma in approx­i­mate­ly three-quar­ters of the peo­ple who had been exe­cut­ed. Their work led to a 2020 National Public Radio analy­sis of more than 200 autop­sies of death-row pris­on­ers exe­cut­ed using lethal injec­tion. That study found that 84% showed evi­dence of pul­monary ede­ma, a con­di­tion in which a person’s lungs fill with flu­id, cre­at­ing the feel­ing of suf­fo­ca­tion or drown­ing that some experts have likened to water­board­ing. Their find­ings were con­sis­tent irre­spec­tive of the state that car­ried out the exe­cu­tion or the drug pro­to­col employed. Autopsy results showed the pres­ence of pul­monary ede­ma in lethal injec­tions involv­ing sodi­um thiopen­tal, pen­to­bar­bi­tal, mida­zo­lam, and etomidate. 

Prior to Mr. Black’s exe­cu­tion, his attor­neys flagged that a sin­gle-drug pen­to­bar­bi­tal exe­cu­tion raised the risk that he would suf­fer from pul­monary ede­ma in vio­la­tion of the Eighth Amendment pro­hi­bi­tion on cru­el and unusu­al pun­ish­ment. But the state’s expert tes­ti­fied in hear­ings pri­or to his exe­cu­tion that Mr. Black would lose con­scious­ness under the pen­to­bar­bi­tal quick­ly — with­in 20 sec­onds. Witnesses to Mr. Black’s exe­cu­tion not­ed that he was still awake and a groan­ing in appar­ent pain five min­utes after the start of the exe­cu­tion, say­ing ​“It’s hurt­ing so bad.” 

Even with the release of Mr. Black’s autop­sy, his attor­neys are still seek­ing addi­tion­al infor­ma­tion. Speaking to the Nashville Banner about ques­tions still unan­swered by the autop­sy, attor­neys for Mr. Black not­ed that the report ​“fails to doc­u­ment the con­di­tion of the veins … [and] to doc­u­ment the EKG results.” His attor­neys are also con­cerned about the admin­is­tra­tion of the pen­to­bar­bi­tal, includ­ing whether prison staff were able to locate a vein, or if they inject­ed the drug into his mus­cle, some­thing that would have cre­at­ed a wound at the injec­tion site. Mr. Black’s team has filed free­dom of infor­ma­tion act requests of the Tennessee Department of Corrections which they expect to be answered by December.