The United States believes the International Committee of the Red Cross is the body that should handle that duty. However, ICRC reports are generally kept confidential, while the U.N. experts almost always make their findings public.
"Fact-finding on the spot has to include interviews with detainees," said Manfred Nowak, the U.N. special investigator on torture and one of the experts. "What's the sense of going to a detention facility and doing fact-finding when you can't speak to the detainees? It's just nonsense."
The five U.N. experts have mandates that cover torture, freedom of religion, health, independent judiciary and arbitrary detention. They started working together in June 2004 to monitor conditions at Guantanamo Bay.
They were appointed to their three-year terms by the 53-nation U.N. Human Rights Commission, the global body's top rights watchdog. The commission has come under criticism because its members include countries with poor human rights records such as Cuba and Zimbabwe, but the experts act independently of the body.
While focusing on individual complaints, the report also constituted a larger rebuttal of U.S. policy in Guantanamo. The experts dismissed U.S. claims that the war on terror constitutes an armed conflict, and said they would not classify the detainees as "enemy combatants."
About 500 people are being held in Guantanamo on suspicion of links to al Qaeda or Afghanistan's ousted Taliban government and charges have been filed against approximately 10 detainees.
The report said the U.S. system of justice for the detainees was unfair and cited poor treatment that included prolonged solitary confinement and sensory deprivation. The experts accused doctors of force-feeding detainees on hunger strike in violation of the U.N. Principles of Medical Ethics and standards adopted by the World Medical Association.
Last week, a Kuwaiti prisoner's lawyer released notes alleging aggressive U.S. military tactics meant to end a hunger strike, including strapping detainees into a restraining chair and denying them throat lozenges to ease the pain of the feeding tubes.
McCormack and other U.S. officials said the U.S. treatment did not violate standard practice.
"I have to tell you that the doctors down there comply with accepted international practice when it comes to these questions," McCormack said. "And this is done by medical professionals in a humane way, according to international practice, when there are those individuals who seek to do harm to themselves by going on hunger strike."