(Washington) - The state of California's new procedure for carrying out executions by lethal injection violates international human rights law, Human Rights Watch said today in a letter to state officials.

California has recently revised its execution procedure in response to criticisms and concerns raised in legal challenges. But the new procedure continues to use a three-drug formula that poses a significant risk of unnecessary suffering, Human Rights Watch said.

"California should follow the example of New Jersey and New Mexico and abolish the death penalty," said David Fathi, director of the US program at Human Rights Watch. "But as long as California carries out executions, international human rights law requires it to make every effort to minimize the prisoner's physical and mental suffering."

At issue is the use of pancuronium bromide, a paralytic agent, as one of the drugs in the execution process. A 2006 Human Rights Watch report, "So Long As They Die: Lethal Injections in the United States," showed that use of this drug creates a risk that an inadequately anesthetized prisoner could be fully conscious and experiencing excruciating pain, yet be unable to move, cry out, or otherwise communicate suffering. The risk that paralytic agents like pancuronium bromide can mask unnecessary suffering is so well recognized that their use in animal euthanasia is banned in California and many other states.

"It's shocking that California plans to put human beings to death using a method that's considered too cruel to use on animals," Fathi said.

The International Covenant on Civil and Political Rights, a human rights treaty ratified by the United States in 1992, does not completely prohibit capital punishment. But it has been interpreted to require that executions be carried out "in such a way as to cause the least possible physical and mental suffering." The Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, ratified by the United States in 1994, also imposes limits on execution methods by prohibiting "cruel, inhuman or degrading treatment or punishment."

Human Rights Watch opposes the death penalty in all circumstances because of its inherent cruelty and finality.