TAZ, JPS, DAL, and LGK conceived the study. TAZ and JPS obtained protocol information and execution data. TAZ, DAL, and LGK analyzed the data and published literature. DAL, LW, and RW provided clinical insights. TAZ, JPS, and FLM provided historical perspectives and references. All authors contributed to writing and editing the manuscript.
JPS practices capital defense. DAL has been a paid expert consultant in death penalty litigation. The other authors have no conflicts to disclose.
Lethal injection for execution was conceived as a comparatively humane alternative to electrocution or cyanide gas. The current protocols are based on one improvised by a medical examiner and an anesthesiologist in Oklahoma and are practiced on an ad hoc basis at the discretion of prison personnel. Each drug used, the ultrashort-acting barbiturate thiopental, the neuromuscular blocker pancuronium bromide, and the electrolyte potassium chloride, was expected to be lethal alone, while the combination was intended to produce anesthesia then death due to respiratory and cardiac arrest. We sought to determine whether the current drug regimen results in death in the manner intended.
We analyzed data from two US states that release information on executions, North Carolina and California, as well as the published clinical, laboratory, and veterinary animal experience. Execution outcomes from North Carolina and California together with interspecies dosage scaling of thiopental effects suggest that in the current practice of lethal injection, thiopental might not be fatal and might be insufficient to induce surgical anesthesia for the duration of the execution. Furthermore, evidence from North Carolina, California, and Virginia indicates that potassium chloride in lethal injection does not reliably induce cardiac arrest.
We were able to analyze only a limited number of executions. However, our findings suggest that current lethal injection protocols may not reliably effect death through the mechanisms intended, indicating a failure of design and implementation. If thiopental and potassium chloride fail to cause anesthesia and cardiac arrest, potentially aware inmates could die through pancuronium-induced asphyxiation. Thus the conventional view of lethal injection leading to an invariably peaceful and painless death is questionable.
Data from executions in the US suggest that current lethal injection protocols do not effect death through the mechanisms intended, and that potentially aware inmates could die through pancuronium-induced asphyxiation.
Lethal injection is a common form of execution in a number of countries, most prominently the US and China. The protocols currently used in the US contain three drugs: an ultrashort-acting barbiturate, thiopental (which acts as an anesthetic, but does not have any analgesic effect); a neuromuscular blocker, pancuronium bromide (which causes muscle paralysis); and an electrolyte, potassium chloride (which stops the heart from beating). Each of these drugs on its own was apparently intended by those who derived the protocols to be sufficient to cause death; the combination was intended to produce anesthesia then death due to respiratory and cardiac arrest. Following a number of executions in the US, however, it has recently become apparent that the regimen as currently administered does not work as efficiently as intended. Some prisoners take many minutes to die, and others become very distressed.
It is possible that one cause of these difficulties with the injections is that the staff administering the drugs are not sufficiently competent; doctors and nurses in the US are banned by their professional organizations from participating in executions and hence most personnel have little medical knowledge or skill. Alternatively, the drug regimens used might not be effective; it is not clear whether they were derived in any rational way. The researchers here wanted to investigate the scientific basis for the protocols used.
They analyzed data from some of the few states (North Carolina and California) that release information on executions. They also assessed the regimens with respect to published data from clinical, laboratory, and veterinary animal studies. The authors concluded that in the current regimen thiopental might not be fatal and might be insufficient to induce surgical anesthesia for the duration of the execution, and that potassium chloride does not reliably induce cardiac arrest. They conclude therefore that potentially aware inmates could die through asphyxiation induced by the muscle paralysis caused by pancuronium.
The authors conclude that even if lethal injection is administered without technical error, those executed may experience suffocation, and therefore that “the conventional view of lethal injection as an invariably peaceful and painless death is questionable.” The Eighth Amendment of the US Constitution prohibits cruel and unusual punishment. The results of this paper suggest that current protocols used for lethal injection in the US probably violate this amendment.
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In the United States, lethal injection can be imposed in 37 states and by the federal government and military. The origin of the lethal injection protocol can be traced to legislators in Oklahoma searching for a less expensive and potentially more humane alternative to the electric chair [
Although executioners invariably achieve death, the mechanisms of death and the adequacy of anesthesia are unclear. Used independently in sufficiently high doses, thiopental can induce death by respiratory arrest and/or circulatory depression, pancuronium bromide by muscle paralysis and respiratory arrest, and potassium chloride by cardiac arrest. When used together, death might be achieved by a combination of respiratory arrest and cardiac arrest due to one or more of the drugs used. Because thiopental has no analgesic effects (in fact, it can be antianalgesic) [
Recently we reported that in most US executions, executioners have no anesthesia training, drugs are administered remotely with no monitoring for anesthesia, data are not recorded, and no peer review is done [
North Carolina lethal injection protocols were determined from Department of Corrections drug procurement records and testimony of prison personnel participating in the process. Times to death were determined from North Carolina Department of Corrections documents including the Web site [
Three lethal injection protocols have been used in North Carolina from the first execution in 1984 to the most recent at the time of this writing in August 2006 (
(A) Schematic depicting quantity and order of drug administration in the three protocols.
(B) Time to death by protocol, calculated as the interval from execution start time to declaration of death, minus 5 min (see
(C) Actual dose of thiopental by body weight (not available for all inmates). In Protocol B, 1.5 g of thiopental was given after the pancuronium bromide and potassium chloride, once painful stimuli had been administered and death should have occurred; accordingly, only the first 1.5 g dose is plotted.
According to the North Carolina Department of Corrections, once the ECG monitor displays a flat line for 5 min, the warden declares death and a physician certifies that death has occurred [
In contrast to clinical use of these same drugs, jurisdictions invariably specify mass quantities for injection rather than dosing by body weight. We sought to determine the actual doses used in executions using postmortem body weights recorded by the Office of the Medical Examiner. North Carolina injects 3 g of thiopental; however, in Protocol B inmates were given half the thiopental at the end, once all painful stimuli were administered and death should have been achieved. Thus we considered only the first 1.5 g for Protocol B. Overall the median thiopental dose was 20.3 mg/kg (range 11.2–44 mg/kg,
Executions in California provided a second insight into the methodologies and outcomes in lethal injections. The public version of the California protocol specifies injection of 5 g of thiopental, 100 mg of pancuronium bromide, and 100 mEq of potassium chloride [
Depicted are duration of respiration and heart rate after initiation of the thiopental injection at time 0. Injection of pancuronium bromide is indicated by the grey arrow, potassium chloride by the black arrow. Note that additional injections of potassium chloride in SA2002 and of pancuronium bromide in WB1996. SW2005 was noted to be breathing 3 min after thiopental, but not at the time of pancuronium bromide injection; the exact time respiration ceased was not recorded. DR2000 was noted to have chest movements two minutes after respiration was noted to have ceased. *A second dose of potassium chloride were administered to CA2006, but not noted on the log. A third, unidentified inmate was also given a second dose of potassium chloride, according to the warden (see text).
Most US executions are beset by procedural problems that could lead to insufficient anesthesia in executions. This hypothesis has been supported by findings of low postmortem blood thiopental levels and eyewitness accounts of problematic executions. Herein we report evidence that the design of the drug scheme itself is flawed
In the United States and Europe, techniques of animal euthanasia for clinical, laboratory, and agricultural applications are rigorously evaluated and governed by professional, institutional, and regulatory oversight. In university and laboratory settings, local oversight bodies known as Animal Care and Use Committees typically follow the American Veterinary Medical Association's guidelines on euthanasia, which consider all aspects of euthanasia methods, including drugs, tools, and expertise of personnel in order to minimize pain and distress to the animal. Under those guidelines, lethal injections of companion or laboratory animals are limited to injection by qualified personnel of certain clinically tested, Food and Drug Administration–approved anesthetics or euthanasics, while monitoring for awareness.
In stark contrast to animal euthanasia, lethal injection for judicial execution was designed and implemented with no clinical or basic research whatsoever. To our knowledge, no ethical or oversight groups have ever evaluated the protocols and outcomes in lethal injection. Furthermore, there are no published clinical or experimental data regarding the safety and efficacy of the three-drug lethal injection protocol. Until the unprecedented and controversial use of bispectral index monitoring in the last two North Carolina lethal injections [
The designers of lethal injection intended that each of the drugs be fatal independently and that the combination provide redundancy [
The most compelling evidence that even 5 g of thiopental alone may not be lethal, however, is that some California inmates continued to breathe for up to 9 min after thiopental was injected. This observation directly contradicts testimony of that state's expert witness, who asserted that “this dose of thiopental sodium will cause virtually all persons to stop breathing within a minute of drug administration” and that “virtually every person given 5 grams of thiopental sodium will have stopped breathing prior to the administration of the pancuronium bromide” [
If thiopental does not reliably kill the inmates, then perhaps death is effected by potassium chloride. Rapid intravenous or intracardiac administration of 1–2 mmol/kg potassium chloride under general anesthesia is considered acceptable for euthanasia of large animal species; thus the 1.11–2.35 mmol/kg doses given in North Carolina's lethal injections ought to be fatal. If potassium chloride contributes to death through cardiotoxicity, however, cardiac activity ought to cease more quickly when potassium is used than when it is not. Indeed, such is the principle behind the animal euthanasia agent, Beuthanasia-D Special, in which the cardiotoxic effects of phenytoin synergize with the central nervous system–depressive effects of pentobarbital, accelerating death over pentobarbital alone [
Given that neither thiopental nor potassium chloride can be construed reliably to be the agent of death in lethal injection, death in at least some inmates might have been due to respiratory cessation from the use of pancuronium bromide. The typical use of 0.06–0.1 mg/kg pancuronium bromide under balanced anesthesia produces 100% neuromuscular blockade within 4 min, with approximately 100 min required for 25% recovery [
Executions such as Diaz's, in which additional drugs were required, constitute further evidence that the lethal injection protocols are not adequate to ensure a predictable, painless death. Court documents and news reports indicate that at least Virginia [
Given the uncertainty surrounding the mechanism of death and low postmortem blood thiopental levels in some executed inmates [
In the modern practice of anesthesia, thiopental is used solely to induce a few moments of anesthesia prior to administering additional agents. Anesthesiologists are taught to administer a small test dose while assessing patient response and the need for additional doses [
Unlike in clinical medicine, however, bolus injection of thiopental is regularly practiced in laboratory animals and veterinary medicine. Standard texts specify from 6 to 50 mg/kg thiopental, depending on the species, for 5–10 min of anesthesia [
Reported Duration of Sleep or Anesthesia after Bolus IV Injections of Thiopental in Experimental Animals
Although species differences complicate pharmacological comparisons from animals to humans, animal studies are the basis for virtually all human drug trials. According to FDA guidelines, toxicity endpoints for drugs administered systemically to animals are typically assumed to scale well across species when doses are normalized to body surface area (i.e., mg/m2) [
Our study is necessarily limited in scope and interpretations. Given the secrecy surrounding lethal injections, we were able to analyze only a small fraction of the 891 lethal injections in the US to date. Indeed, the majority of executions actually take place in states such as Texas and Virginia, where the protocols and procedural problems are likely similar to the ones described, but where the states are unwilling to provide information [
Despite such limitations, our analysis of data from more forthcoming states along with reports of problematic executions and judicial findings [
With the growing recognition of flaws in the lethal injection protocol, 11 states have now suspended the death penalty, with nine of those seeking resolution of issues surrounding the process [
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