There are unequivocal points to be made within the debate now raging in the United States over the Bush administration's use of what it described in its sanitized parlance as 'enhanced interrogation techniques' to wring information from detainees suspected of terrorism — techniques better described as torture.

Despite plausible-sounding talk about 'states of induced dependency' and the like, there is no scientific basis for asserting that techniques such as waterboarding, or slamming people against a wall, are fast or effective ways of getting at the truth (see Nature 445, 349; 2007). Indeed, it is hard to imagine any ethical way a controlled study on that question could be carried out. What is known to work — and surprisingly rapidly, according to field anthropologists, investigative journalists, police detectives and others with practical experience at getting information from reluctant or hostile sources — are the 'soft' methods of building rapport and trust.

And even if physical or mental torture could be shown to be effective in some immediate, tactical sense, that would be beside the point: torture is a violation of human rights and of international law, and is a threat to the long-term health of democracy. It is not to be tolerated.

Beyond that, there are few easy answers. Witness the struggles by the American Psychological Association (APA) to lay out ethical guidelines for psychologists involved in US national-security-related interrogations such as those that took place at Guantanamo Bay in Cuba.

The discussions, which were made public earlier this month on the non-profit news site ProPublica, were carried out on a confidential listserv in 2005 and involved the ten members of the APA Task Force on Psychological Ethics and National Security. Their work led to a set of 12 principles that were issued in a 2005 report (www.apa.org/releases/pens0705.html).

The most inflammatory issue, now that the task force's work has been thrust back into the limelight, is that six of its members were on the Pentagon's payroll. This might seem reasonable: guidelines should be informed by people who know what they're talking about. But it has led the Massachusetts-based activist group Physicians for Human Rights, among others, to charge the APA with having excessively cosy relations with the military on torture — or, at the very least, with letting the Pentagon dictate a set of guidelines to its own liking.

The evidence for this is not obvious in the 12 principles themselves. One forbids psychologists to engage in, direct, support, facilitate or offer training in torture or other cruel, inhuman or degrading treatment; another articulates a moral obligation for them to report acts of torture to the “appropriate authority”. But the very fact that collusion charges have been made suggests how sensitive the subject is.

Another, long-standing issue for many APA members can be found in the first of the 12 principles, which explicitly states that it is ethical for psychologists to be involved in interrogations. Other professional societies have taken a less permissive tack; the American Medical Association, the American Psychiatric Association and the World Medical Association have all come out against having their members participate in interrogations.

But such restrictions fly in the face of the reality that interrogation is a necessity in preventing loss of life from terrorism, and that some professionals feel it is their duty to ensure that the activity is conducted responsibly. The risks of abuse are ever present, and having a professional present should serve as protection for detainees, provided the professional adheres to, and is held accountable to, the most fundamental medical ethic of all: 'do no harm'.

Mike Gelles, a task-force member who was at the time chief psychologist for the Naval Criminal Investigative Service, maintains that his active involvement at Guantanamo Bay allowed him to bring concerns about interrogation methods to military leaders there, leading them to change those methods. He deserves the last word. “Removing professional psychologists from these settings,” he wrote in 2007 to colleagues who were calling for a moratorium on psychologists' involvement in interrogations, “will impact the degree of oversight and inevitably increase the likelihood of abuse, thus having precisely the opposite effect of what occurred as a result of my involvement at Guantanamo Bay.”