Execution by lethal injection: Autopsy findings of pulmonary edema

Lethal injection is the common method of capital punishment in the United States (US), but problematic executions feed controversy centered on the 8th amendment of the US constitution that proscribes cruel punishment.1 However, the definition of cruelty is contentious, and lethal injection displays few signs of the hidden course of a potentially cruel death. Few survive and those who die cannot give witness. In this study, we reviewed autopsy reports of prisoners executed by intravenous midazolam (usually followed by a neuromuscular blocking agent and potassium chloride) or pentobarbital as a single drug. Autopsy reports for 43 inmates obtained from eight states were reviewed to identify any abnormal findings. Pulmonary edema (often fulminant with froth filling airways) emerged as a consistent and unexpected abnormality in 33/43 autopsies (76.74%), 23/28 midazolam executions (82.14%), and 10/15 (66.66%) pentobarbital executions. Injecting heavy overdoses of either acidic or basic solutions into the bloodstream may be directly toxic to pulmonary capillary endothelial cells. The injury manifests by the sudden escape of edema fluid into normally air-filled lungs, resulting in pulmonary edema. These findings explain witnessed respiratory distress during executions and increase concern about an inability of an execution witness to observe such a finding when a paralytic is added.