An editorial from Scientific American:
The idea of testing how to most effectively kill a healthy person runs contrary to the spirit and practice of medicine. Doctors and nurses are taught to first “do no harm”; physicians are banned by professional ethics codes from participating in executions. Scientific protocols for executions cannot be established, because killing animal subjects for no reason other than to see what kills them best would clearly be unethical. Although lethal injections appear to be medical procedures, the similarities are just so much theater.
Yet even if executions are not medical, they can affect medicine. Supplies of propofol, a widely used anesthetic, came close to being choked off as a result of Missouri's plan to use the drug for executions... The manufacturer feared that if the drug was used for lethal injection, E.U. regulators would ban all exports of propofol to the U.S....
Propofol is the most popular anesthetic in the U.S. It is used in some 50 million cases a year—everything from colonoscopies to cesareans to open-heart surgeries—and nearly 90 percent of the propofol used in the U.S. comes from the E.U. After 11 months, Missouri relented and agreed to return the drug.
Such incidents illustrate how the death penalty can harm ordinary citizens.