UNITED NATIONS (AFP) - A senior UN human rights investigator on Monday criticised the US justice system as flawed and called on authorities to ensure it does not execute innocent people. Philip Alston, the United Nations special rapporteur on extra-judicial, summary and arbitrary executions, blasted the administration of President George W Bush for lack of transparency at the Guantanamo detention camp, and slammed state authorities in Alabama and Texas for being "strikingly indifferent" to the risk of putting innocent people to death. "At present, a great deal of time and energy is being spent trying to expedite executions" in the United States, Alston told a press conference after a two-week fact-finding tour. "A better priority would be to analyse whether the criminal justice system is failing in capital cases and why innocent people are being sentenced to death." Alston, an Australian, wrapped up a two-week tour of the United States including Washington DC, New York, Alabama and Texas, during which he met government officials, judges, civil society groups and victims and witnesses. He reserved a special barrage of criticism for Alabama, which has the highest per capita rate of executions in the country, and Texas, which has the largest number of executions as well as prisoners on death row. "It is entirely possible that Alabama has already executed innocent people, but officials would rather deny than confront flaws in the criminal justice system," Alston said. He said that since 1973, 129 people on death row in the United States have been exonerated and that the number continues to grow. As for the US-run prison in Guantanamo, Alston expressed concern for the six "alien unlawful enemy combatants" currently detained at the US naval base in Cuba who face war crimes charges under special military tribunals. The prisoners face the death penalty if convicted in the military trials. "These trials utterly fail to meet the basic due process standards required for fair trial and international humanitarian and human rights law," he said. He highlighted that access to counsel was limited and hearsay evidence was allowed in the military trials, and that the act's rules allowed "coerced statements" obtained during interrogations. He also said that at least one of the detainees facing trial has been subjected to "waterboarding," a simulated drowning technique denounced by rights groups as torture. But he said the Military Commissions Act that created the tribunals "does not prohibit all coerced statements from being admitted into evidence." Referring to five deaths of inmates at Guantanamo in 2006-07, Alston called for the government to make public the investigations of those cases and release autopsies to the families of the deceased men. "The Department of Defence has provided little public information about the cause or circumstances of any of these deaths," he said. Alston described the US military justice system as "troublingly opaque," and called for greater transparency. "Procedural and other impediments are firmly ensconced in order to thwart those who seek to monitor the accountability of public authorities," he said. However, Alston said transparency could be achieved quickly and easily. "Reporting requirements and a central office or registry could be added to the existing system at little cost and this would markedly improve accountability," he said.