In addition to his concerns that some forms of execution - such as stoning and gas asphyxiation - have been "explicitly deemed to violate the prohibition of torture," Mendez noted that "[s]olitary confinement ... in combination with the knowledge of death and uncertainty of when an execution would take place, contributed to the risk of irreparable mental and physical harm." And, of course, there is evidence suggesting that even lethal injection is not as pain-free as some would like to believe.
In response, the U.S. delegate defended the death penalty by saying that "the report noted that the death penalty could only be carried out pursuant to the judgement of competent courts and applied only to the most serious crimes. The United States had a number of exhaustive protections to ensure that the death penalty was undertaken with the best safeguards and only after multiple layers of judicial review."
But try telling that to the family of Cameron Todd Willingham, who was executed in Texas in 2004 for an alleged arson murder only to have a later forensic review conclude that "a finding of arson could not be sustained." In other words, the fatal fire for which Willingham was executed was probably an accident. So much for safeguards.
But whether the condemned is actually innocent or not is beside the point that Mendez was making. So are the "exhaustive protections" claimed by the U.S. delegate. Unfortunately, to some it doesn't matter.