The US Secretary of State Condoleezza Rice’s defence of the practice of transferring prisoners around the world for interrogation relies a great deal on a definition of torture.



In the US view, torture has to involve "severe pain" and harsh interrogations do not necessarily amount to torture.



Ms Rice accepted that prisoner transfers, known as "renditions", take place and said they were not unusual. The French had moved Carlos the Jackal directly from Sudan that way in 1994, she pointed out.



She did not adddress the issue of where these prisoners, thought to be senior al-Qaeda suspects like Khaled Sheikh Mohammed, the man who thought up the attacks of 9/11, end up.



The Washington Post has alleged that there are or have been secret CIA prisons in Eastern Europe, Afghanistan and Thailand. By being located outside the US, they would avoid coming under the scrutiny of US courts.



But as she set off a European visit during which the rendition flights and the ultimate aim of such flights will be a key issue, the Secretary of State stressed several times that the United States did not engage in torture.



And it is really the torture issue which is the key. If the flights were simply for the purpose of moving prisoners between open court systems, nobody would complain.



It is the idea that they are tortured in secret detention camps that has concerned critics and has forced Ms Rice to issue her statement.



The United States acted, she said, in accordance with its legal obligations, among which is the 1984 UN "Convention against Torture and other Cruel, Inhuman and Degrading Treatment or Punishment.



This defines torture as follows: "Torture means any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession, punishing him for an act he or a third person has committed or is suspected of having committed, or intimidating or coercing him or a third person, or for any reason based on discrimination of any kind..."



It will be seen that a lot depends on the definition of "severe."



In a memorandum on 1 August 2002, the then Assistant US Attorney General Jay Bybee said that "the adjective severe conveys that the pain or suffering must be of such a high level of intensity that the pain is difficult for the subject to endure."



He even suggested that "severe pain" must be severe enough to result in organ failure death.



Such an interpretation would obviously leave an interrogator a great deal of latitude, and that memo was subsequently disowned by the Bush administration.



What seems to have evolved is a series of interrogation techniques which in the US view do not amount to torture as defined by the UN Convention but which go beyond the simple business of asking questions.



Recent reports on the American ABC News network, quoting CIA sources, listed six so-called "Enhanced Interrogation Techniques."



1. Grab: the interrogator grabs a suspect’s shirt front and shakes him.



2. Slap: an open-handed slap to produce fear and some pain.



3. Belly Slap: a hard slap to the stomach with an open hand. This is designed to be painful but not to cause injury. A punch is said to have been ruled out by doctors.



4. Standing: Prisoners stand for 40 hours and more, shackled to the floor. Said to be effective, it also denies them sleep and is part of a process known as sensory deprivation ( this was a technique used by British forces in Northern Ireland for a time until it was stopped).



5. Cold Cell: a prisoner is made to stand naked in a cold, though not freezing, cell and doused with water.



6. Water Boarding: the prisoner is bound to a board with feet raised, and cellophane wrapped round his head. Water is poured onto his face and is said to produce a fear of drowning which leads to a rapid demand for the suffering to end.



Some or all of these techniques might be outlawed if the US Senate has its way. The Senate has approved by 90 to 9 a measure outlawing "cruel, inhuman, or degrading treatment or punishment."



Again, much depends on definitions but President Bush apparently feels that McCain’s amendment would prevent the CIA from carrying out "enhanced" interrogation. He is threatening to veto the Bill onto which this prohibition has been tacked as an amendment. The White House and McCain, a former pilot who was himself tortured by the North Vietnamese, are trying to reach a compromise.



Senator McCain has written against any ill-treatment of prisoners: "We should not torture or treat inhumanely terrorists we have captured. The abuse of prisoners harms, not helps, our war effort. In my experience, abuse of prisoners often produces bad intelligence because under torture a person will say anything he thinks his captors want to hear - whether it is true or false - if he believes it will relieve his suffering," he said in an article in Newsweek.



He is particularly against "waterboarding". "I believe that it is torture, very exquisite torture," he said.



But the administration clearly feels that the CIA’s hands should not be tied too tightly.



Stephen Hadley, the US National Security Adviser, has spoken of the dilemma faced by governments which say they abide by the rule of law yet which need to get information to save lives.



"The president has said that we are going to do whatever we do in accordance with the law. But you see the dilemma. What happens if on September 7th 2001, we had gotten one of the hijackers and based on information associated with that arrest, believed that within four days, there’s going to be a devastating attack on the United States?"



One very grey area of the rendition policy is that sometimes a prisoner is handed over secretly to a country which itself carries out the interrogation. Such a country might not be so particular as to the methods used.



There is a view among some lawyers that the US would violate international law if it knew of such practices by governments to which it hands over suspects.