L ast July, convicted murderer Joseph Rudolph Wood took more than 640 gulps of air as he lay dying for nearly two hours in the execution chamber of an Arizona prison. One reporter described it as “drowning in air.” The state had administered an experimental two-drug combination including the sedative midazolam and the painkiller hydromorphone. By the time Wood died, he had been injected with 15 times the amount of lethal chemicals originally planned.

The Wood execution was the third instance in 2014 alone of experimental combinations of drugs resulting in executions that did not go as expected. In Ohio, Dennis McGuire was also reported to have gasped for air after the injection of a similar two-drug protocol; it took him 26 minutes to die. In Oklahoma, Clayton Lockett died from a heart attack after another experimental mixture failed to kill him.

On Wednesday, the Supreme Court is scheduled to hear oral arguments in Glossip v. Gross and will consider whether the Lockett execution amounted to cruel and unusual punishment.

With this case in mind, The Marshall Project compared two ways this country legally dispenses death: the execution of death-row prisoners and the euthanizing of incurably sick dogs and cats. See if you can guess which rules apply to which category of condemned creature.