Lethal injection (search), when used for the first time in Texas nearly 22 years ago, was touted as a more humane way to execute prisoners than the firing squad, hanging, the gas chamber or even the electric chair. Today, though, death penalty opponents are challenging that notion based on the Constitution's Eighth Amendment (search), which prohibits "cruel and unusual punishments inflicted."

Attorneys in at least a dozen of the 37 states that use lethal injection have filed lawsuits seeking to ban the procedure, which they say puts inmates through excruciating pain because the anesthetic wears off before the two other drugs are injected.

Prosecutors and victims rights advocates call the lawsuits "the appeal du jour."

"It is clear that no method would be acceptable to those who oppose capital punishment in principle," said Pete Adams, executive director of the Louisiana District Attorney's Association (search). "It should be remembered that anti-death penalty advocates see their cause as a long-term campaign to be waged on many fronts."

The most recent anti-death penalty action was brought in civil court in Kentucky. Earlier this year, New Jersey stopped lethal injections after an appeals court found insufficient medical knowledge to support the procedure.

The Kentucky case involves two convicted murderers, Thomas Clyde Bowling and Ralph Baze. Their lawyers argue that Bowling and Baze "will ... be tortured to death" if the state executes them by lethal injection.

A lethal injection is comprised of an anesthetic, a paralytic drug and potassium chloride, which causes cardiac arrest.

Pennsylvania state Rep. Daylin Leach has proposed eliminating the paralytic drug from that state's lethal injection. Not using it may show whether inmates are unconscious when receiving potassium chloride or if they are awake and just unable to speak, Leach said. Someone squirming and screaming in pain as the lethal dose is administered could be enough to prompt states to refine the procedure, he said.

"It seems to me that the only reason we are using it is to protect the aesthetic sensitivities of the witnesses to the execution," Leach said.

Carol Weihrer of Reston, Va., testified before the Pennsylvania lawmakers about how the anesthesia she was given for eye surgery didn't work, but the drug she was given to paralyze her did — meaning she couldn't alert her doctors that she was awake. She felt no pain from the cutting, because the painkilling portion was effective, but the tremendous pressure exerted to remove the eye was painful in its own way.

"It looked pretty boring," Weihrer said about a video of her surgery. "It was quite painful."

Death penalty proponents say they don't believe inmates feel pain during a lethal injection.

"Science does not support the rhetoric," said Dianne Clements, president of Justice For All (search), a Houston, Texas-based victim's rights group.

Wayne Uber, the director of the North Carolina victims assistance network, said the only pain prisoners may feel is temporary discomfort when the needle is inserted.

"Lethal injections, as they are currently performed in the United States, represent the most humanely possible means of executing a condemned murderer," Uber said.

Anesthesiologists and activists do not agree whether the initial anesthesia keeps an inmate unconscious throughout an execution.

Texas state Sen. Kyle Janek (search), an anesthesiologist, said the amount of anesthesia given in lethal injections is 10 times more than the dosage given to a patient going into surgery. That dose basically guarantees the inmate is not awake as the other drugs are administered, Janek said in written testimony to a Pennsylvania legislative committee considering Leach's proposal.

But Columbia University anesthesiologist Mark Heath said the paralyzing drug makes it impossible to know if the condemned inmate is feeling pain.

There is no national consensus on how much anesthesia to give an inmate and no way to guarantee the condemned stays unconscious throughout the procedure, said Heath, who testified with Weihrer before the Pennsylvania legislative committee.

In Kentucky, lethal injections will continue unless some proof of a problem arises, said Vicki Glass, a spokeswoman for the state attorney general's office.

"The court should not prevent the implementation of the sentence imposed by the judge and jury," Glass said.