According to international standards restraints may be used when strictly necessary as a precaution against escape, damage or injury. However, if restraints are necessary, they must be applied humanely, with adequate opportunity for the prisoner to move limbs, use the bathroom and eat and drink.

Furthermore, sedating prisoners for other than medical purposes would be in breach of international standards. According to Principle 5 of the UN Principles of Medical Ethics any administration of sedative drugs should be in accordance with purely medical criteria.

In a letter to the authorities earlier this week Amnesty International expressed concern at photos showing detainees in Afghanistan hooded while under guard by US marines. Hooding suspects in detention may violate international standards prohibiting 'cruel, inhuman or degrading' treatment. The standards emphasise that the term 'cruel, inhuman or degrading' covers mental as well as physical abuse, including holding detainees in conditions that deprive them, even temporarily, of the use of any of their natural senses such as sight or hearing or awareness of time or place. The hooding or blindfolding of suspects during interrogation also violates international standards.

'Housing detainees in Guantanamo in 6x8-feet chain-link 'cages' at least partially open to the elements would also fall below minimum standards for humane treatment,' the organisation said. Standards for the treatment of detainees require adequate shelter from the elements. The cage size would be less than that considered acceptable under US standards for ordinary prisoners confined to cells.

The letter sent to US authorities is available on by visiting www.amnesty.org