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Police in India are reportedly to use the so-called "truth serum" sodium pentothal on a man they suspect to be involved in the attacks that claimed 170 lives in Mumbai. So how reliable is it?
Truth serum has appeared in the plot of Spooks
It sounds like a far-fetched James Bond scenario - a drug that makes people tell the truth.
But even the Ancient Romans noted how consumed substances can make people less partial to fibs, coining the phrase "In vino veritas" which means "In wine there is truth".
Thousands of years on, police in India are said to be considering the use of sodium pentothal as they question a man they accuse of being involved in the attacks in Mumbai. They have been known to use it as an aid to questioning in previous criminal investigations.
Sodium pentothal - also known as thiopental - is a barbiturate that acts on the receptors in the brain and the spinal cord.
Psychiatrists in the UK prescribe it for the treatment of phobias. And its anaesthetic properties mean it is one of the drugs administered in lethal injections in some US states.
Like alcohol, sodium pentothal can loosen people up and make lying more effort than telling the truth
But it is not considered a reliable technique
Evidence obtained in this way is not admissible in court
It has the effect of diminishing activity in part of the brain, in practice removing inhibitions and making people chatty. Those who advocate its effectiveness as a "truth drug" believe that by relaxing an individual in this way, the person will find it harder to lie than to to tell the truth. So is it effective?
"Telling lies is hard work and requires considerable mental effort," says Michael Enders, a criminologist and interrogation specialist based in New South Wales, Australia.
"Anything that reduces the subject's capacity to carry out this mental work can give the impression that it is a 'truth serum'. For instance, alcohol, in some circumstances, can give results.
"People who are drunk find it easier to tell the truth rather than lie, so they tell the truth. Many drugs provide similar results."
But if a drug was found to provide reliable results with minimal risks to the subject, it would be in widespread use, especially given the lengths to which the US, former Soviet Union and other countries have gone to in order to "interrogate" subjects, he says.
Also, the number of double agents who have avoided detection suggests either no such drug exists or it has limited effect.
Some psychiatric researchers have claimed that it is possible to lie under the influence of pentothal, says Alison Winter, an expert in the history of modern medicine at the University of Chicago.
"But the more common view is that drugged patients have less control over what they say in the drugged state than in a sober one, so it is less likely that a deliberate lie can be perfectly maintained as easily in this state as in an undrugged one."
However, a more common problem with the reliability of information given under the influence of sodium pentothal, she says, is that subjects pick up on hints from interlocutors more readily than they would in an ordinary state of mind.
So someone who is drugged might make a false statement because he or she is responding to a deliberate or unconscious cue.
There were calls in the US for drugs to be used on men arrested in the wake of the 11 September attacks, but while their use in the questioning of prisoners of war is forbidden by the Geneva Convention, that does not rule out its lawful use on terror suspects.
However, statements made by people under the influence of drugs are not admissible in the courts of many countries, including the US, the UK and India. In the UK, the use of a needle by police could also constitute assault.
Dr Winter says the term "truth serum" was first used in Texas in about 1920, to describe the work of obstetrician Dr Robert House, who noted that when under the anaesthetic drug scopolamine, his patients would answer questions in a way that appeared automatic.
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In the 1920s, he replaced scopolamine with sodium pentothal or sodium amytal and by then he was using it on defendants in court, to validate claims of innocence, at a time when there was some concern in the US about interrogation and false confessions.
"This is an ironic beginning for the idea of a 'truth serum', because in later years it was more commonly associated with coercive interrogations - as a way of trying to extract truthful statements from people, whether or not they consented to the procedure," says Dr Winter.
During and after World War II, it was used in military psychiatry to help traumatised soldiers to articulate what had happened to them, says Dr Winter.
And in the 1950s and 60s, the CIA researched the use of sodium pentothal as part of a wider look at the effectiveness of drugs such as LSD in the controversial Project MK-ULTRA. Many people were given substances without their knowledge or consent.