Although people may balk at the idea of comparing the killing of animals in shelters to the execution of human prisoners, some legal activists believe this is just what we need to do. Indeed, our method of killing animals is more humane, they say, than how we kill capital offenders. The three-drug protocol used in executions is considered inhumane for animals.

Most killing of animals in shelters and pounds across the country is now accomplished through injection of a lethal dose of barbiturate, usually sodium pentobarbital. After the solution is injected into a vein or sometimes, depending on the type of animal, into the heart, the animal slips almost immediately into unconsciousness and then dies. This procedure, called EBI (euthanasia by injection) in shelter lingo, is considered by veterinarians and animal advocates to be the most humane method of killing these animal inmates. (Unfortunately, some shelters and pounds still use other methods, such as gas chambers, based on a mistaken belief that EBI is more expensive.)

Though lethal injection of prisoners has obvious parallels to EBI, the protocol is different. And this is no coincidence. As states were considering the adoption of lethal injection during the 1970s, they consulted with veterinarians. Ultimately, though, legislators ignored the advice of vets, who recommended the use of a single anesthetic drug, sodium pentobarbital. Instead, states uniformly adopted a three-drug protocol. Three drugs are administered, one immediately after the other: sodium thiopental (an anesthetic), pancuronium bromide (a paralytic), and potassium chloride (which stops the heart). According to an analysis by Ty Alper in the Fordham Urban Law Journal, the reason the three-drug protocol was adopted had much to do with animals: legislators were afraid that the public would object to "treating people the same way we're treating animals." Ironically, though, the three-drug protocol turns out to be far less reliable, and far less humane than the single-drug method. As a matter of fact, Alper notes that roughly 98% of all lethal injection executions in the U.S. occur in states that have banned the use of the same combination of drugs for euthanasia of animals.

The controversy over lethal injection revolves around the second of the three drugs, pancuronium. Pancuronium is a neuromuscular blocking agent: it paralyzes the inmate, but does nothing to blunt the sensations of pain. The third drug, potassium chloride, causes "excruciating pain that has been likened to the feeling of having one's veins set on fire." If the first drug, the anesthetic, happened to fail, the inmate would, with the second drug, be rendered "unable to cry out or even blink an eyelid to let anyone know" that he was fully aware and awake when the potassium chloride was shot into his veins.

Onlookers would have no idea because, as Alper notes, "pancuronium virtually ensures that the execution looks 'peaceful' when it may have been anything but."

Pancuronium is derived from (or synthesized to mimic) curare, a poisonous extract derived from a South African plant. As Alper explains, the nuances of curare—what it does and doesn't do—were discovered during the course of vivisection on animals. Curare was a boon to physiologists dissecting animals because it would render a creature fully cooperative yet at the same time very much alive and completely conscious. Alper quotes the 19th century physiologist Claude Bernard:

"In this motionless body, behind that glazing eye, and with all the appearance of death, sensitiveness and intelligence persist in their entirety. The corpse before us hears and distinguishes all that is done around it. It suffers when pinched or irritated, in a word, it still has consciousness and volition, but it has lost the instruments which serve to manifest them." 

Once it was understood that curare paralyzed but did not anesthetize, its use in animals grew increasingly controversial, and the use of paralytics has become less and less acceptable. You can still find scattered accounts of veterinarians or researchers using the paralytic drug succinylcholine chloride, either as a form of so-called chemical restraint during surgery or experimentation (sometimes without the accompanying use of an anesthetic), or as a lethal injection. And you find an occasional use of a euthanasia solution called T-61, which is very much like the three-drug combination used in human executions. Yet almost without exception, the use of neuromuscular blocking agents in animal euthanasia is considered unethical. The vast majority of animal euthanasia is carried out by means of sodium pentobarbital, and there is strong consensus among humane organizations and veterinary groups that this is the single most humane euthanasia method.

Although the Supreme Court has not yet ruled the three-drug protocol for capital punishment unconstitutional, some states are moving toward a one-drug method. Ohio and Washington have both made the switch. The website notes that some of the states with the most explicit ban on paralyzing drugs for animal euthanasia are the most active in capital punishment.

The comparisons are uncomfortable from many angles. We often refer to criminals as "animals" (though ironically, deliberate cruelty is thought to be a uniquely human trait). It is perhaps a stretch, too, to call the killing of animals in shelters a form of punishment for the crimes of being unwanted, fractious, unable to conform to human standards of behavior, or in the wrong place at the wrong time. Still, it is worth looking at state-sanctioned killing in its various forms and using the comparisons to think about the humaneness of our actions.

One piece of good news: the number of prisoners executed in the U.S. has been gradually declining. In 2011, 13 states have executed 43 inmates. 46 were executed in 2010, and 52 in 2009. The number of animals killed in U.S. shelters seems also to be very slowly inching downwards. A 2011 analysis of shelter data by Animal People magazine (see the July-Aug. 2011 issue) reported that a mere 1,555,511 dogs and 1,865,375 cats had been killed, the lowest numbers in about fifty years.

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