Washington ? Supreme Court justices clashed on Wednesday over how states execute killers, with one court member saying current lethal-injection drugs would not be used on cats and dogs and a second arguing that executions do not have to be pain-free.

The court blocked Florida, at the last minute, from executing Clarence Hill in January, as Hill lay on a gurney with IV lines in his arms.

The justices agreed to consider the way states carry out capital punishment. The court’s ruling, expected before July, will determine whether inmates can file last-minute civil rights challenges claiming their deaths would be cruel and unusual punishment.

“Your procedure would be prohibited if applied to dogs and cats,” Justice John Paul Stevens told Florida’s assistant deputy attorney general, Carolyn Snurkowski.

On the other side, Justice Antonin Scalia said the Constitution does not require painless deaths. “Hanging was not a quick and easy way to go,” he said, referring to one of the country’s oldest execution methods.

Critics of lethal injection have been bolstered by a 2005 study published in the Lancet medical journal indicating that a painkiller administered at the start of an execution can wear off before a prisoner dies.

Florida’s three-drug combination is similar to that used in other states. The painkiller sodium pentothal is followed by a chemical, pancuronium bromide, that paralyzes the inmate. The final drug is potassium chloride, which causes a fatal heart attack.

Florida is one of 30 states that restrict the use of an agent such as pancuronium bromide in euthanizing animals, justices were told in a brief by three veterinarians. The veterinarians said “its only effect is to mask any suffering endured by the patient.” They said that the Florida protocol does not meet standards for animals.

Several justices appeared surprised that the state has laws that spell out how animals should be euthanized, but that there are no guidelines for how prison officials should execute people.