The Supreme Court heard arguments Jan. 7 for a case that since September of last year has put executions across the United States in limbo. Death row inmates Ralph Baze and Thomas C. Bowling, both convicted in Kentucky of double murders, are challenging their sentences on the grounds that Kentucky's three-drug lethal injection protocol may in some accidental instances cause, in the words of attorney Donald B. Verrilli Jr., "torturous, excruciating pain."

If Verrilli convinces the court that Kentucky's procedure-also used in 34 other states-violates the inmates' constitutional protection against "cruel and unusual" punishment, many states will be forced to continue a moratorium on executions until they discover a constitutionally acceptable method.

The execution protocol in question involves three chemicals injected intravenously in successive order:

According to Verrilli, if the initial drug is administered improperly-for example, through a badly placed IV line-inmates might remain conscious and feel excruciating pain as the second two drugs circulate their bloodstream. Yet because of the paralyzing agent, they would be unable to show any outward signs of pain. By contrast, Kentucky state law requires animals to be euthanized using a single, large dose of barbiturates.

Guidelines from the American Veterinary Medical Association prohibit the use of potassium chloride in euthanasia unless a qualified technician can determine the animal is in a "surgical plane of anesthesia." (Several leading hospitals have approved lethal injections of potassium chloride as standard procedure in late-term abortions following the court's upholding a ban on the partial-birth abortion procedure.) Verrilli argues Kentucky's lethal injection procedure is less stringent for humans than for animals, since it doesn't require a technician to monitor the inmate's anesthesia.

But as Verrilli presented his case to the court, both conservative and more liberal justices on the bench seemed skeptical.

Justice Stephen G. Breyer: "I understand your contention. You claim that this is somehow more painful than some other method. But which? And what's the evidence for that? What do I read to find it?"

When the attorney suggested a large dose of barbiturates as an alternative, Chief Justice John G. Roberts Jr. responded that another appeal might be "brought by someone subject to the single-drug protocol, and their claim is, 'Look, this has never been tried.'"

Justice Antonin Scalia: "This is an execution, not surgery. . . . Where does that come from, that you must find the method of execution that causes the least pain? We have approved electrocution. We have approved death by firing squad. I expect both of those have more possibilities of painful death than the protocol here."

Lawsuits challenging execution methods and sentencing procedures have a long-standing history, dating back to the influence of Declaration of Independence signer Benjamin Rush, who prompted Pennsylvania to establish the nation's first penitentiary and become the first state to abolish capital punishment for all crimes except first-degree murder.

In a much later, landmark 1958 case, the Supreme Court ruled the Eighth Amendment's "cruel and unusual" clause had to be interpreted under society's "evolving standards of decency." In subsequent cases some individual justices have questioned whether capital punishment is ever appropriate.

But during this month's oral arguments before the high court, justices pressured Verrilli to present stronger evidence that the current injection protocol, as practiced, presents a reasonable risk of unnecessary pain, or that a more acceptable alternative is available. "There will always be some claim that there is some new method of execution devised and once again executions are stayed throughout the country," said Scalia, warning of future litigation once this case is "decided."

Executive stats

Timeline of capital punishment in America

1641: Massachusetts Bay Colony codifies 12 capital crimes, including idolatry and adultery.

1791: The Bill of Rights is adopted, providing protections to those accused or convicted of crimes in the United States.

1794: Pennsylvania abolishes the death penalty for all crimes except first-degree murder.

1879: The Supreme Court rules death by firing squad to be constitutionally acceptable in Wilkerson v. Utah.

1890: The Supreme Court upholds the use of the novel "electric chair," and William "Willie" Kemmler becomes the first to die in it.

1924: Gee Jon becomes the first to be executed in a gas chamber after his Supreme Court appeal is rejected.

1958: In Trop v. Dulles, the Supreme Court determines "evolving standards of decency" must govern the propriety of capital punishment.

1967: A 10-year moratorium on executions begins pending challenges to the death penalty's constitutionality.

1972: In Furman v. Georgia, the Supreme Court rules capital punishment as then practiced to be unconstitutional, commuting over 600 death sentences.

1976: The Supreme Court rules capital punishment to be constitutionally acceptable under newly crafted state laws.

1982: In Texas, Charlie Brooks becomes the first to be executed by lethal injection.

1985: The Supreme Court rejects the argument that lethal injection drugs not regulated by the FDA areunconstitutional.

2005: The Supreme Court rules criminals may not be executed for offenses they committed while under 18 years old.