COPENHAGEN - Thirty-two states and the federal government have the death penalty, and all of them use lethal injection, with various drugs, as the primary method. It has been used in the United States more than 1,200 times.
Many states, including Oklahoma, have been having trouble getting a hold of the execution drugs.
The reason several states are running short is a woman named Maya Foa. She works for a British group which campaigns against the death penalty.
"I don't believe there's such a thing as a humane execution," she said. "We have executions which are lasting 25 minutes, and the prisoner's dying in agony. That for me as a form of 'just' punishment is a contradiction in terms."
In 2011, Foa began researching pentobarbital, the drug most commonly used in U.S. executions.
It was developed to treat epilepsy, but in the high doses used in lethal injections it causes respiratory arrest.
Foa discovered that the only company with approval from the Food and Drug Administration to sell pentobarbital in the U.S. was a Danish group called Lundbeck.
The death penalty has been banned in the European Union so she made the information public, hoping to force Lundbeck to stop selling pentobarbital to U.S. prisons.
"It was a scandal," Foa said. "It was extraordinary. It was a scandal. It was a big deal in Denmark, and it was a real problem for the company."
At Lundbeck's headquarters in Vopenhagen, communications chief, Anders Schroll, told us Lundbeck had not known its epilepsy drug was being used in executions.
"That was certainly a shock for Lundbeck because this is completely against what we stand for," Schroll said. "Our researchers go to the lab every day to save people's lives, and this is completely against why they work."
With Foa's help, Lundbeck developed a new sales system to control who purchased their drugs.
That has shut down the supply of FDA-approved pentobarbital to U.S. prisons, and led 10 other pharmaceutical companies to follow suit, to stop their drugs being used in executions.
One of the consequences of what Foa has done is that some U.S. states are now turning to new, untested drugs that may cause more suffering than pentobarbital.
"We can make sure that our products are used for what they're meant for," Schroll said. "The rest is up to society, to U.S. citizens to find out whether or not they should have capital punishment."But the shortage of pentobarbitol has drawn attention to how much executed prisoners suffer.