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What is truth serum?

Indian officials plan to inject captured Mumbai terrorist with the "truth serum," sodium pentothal, but history tells us that the technique isn't up to the task



© iStockPhoto / Stefan Klein

The baby-faced gunman of Mumbai, Azam Amir Kasab,  now in the custody of Indian police, is the sole surviving attacker in the three-day rampage that began on the night of November 26 and left more than 170 people dead and scores of others injured.

After the attacks, Indian officials immediately began pointing fingers at longtime rival, Pakistan, as the source of the 10 militants—a charge that Pakistan President Asif Ali Zardari disputed last night on CNN. During police interrogations, Kasab himself claimed to hail from the Punjab region of Pakistan and to have trained with the Pakistan-based extremist group, Lashkar-e-Taiba.

Of course, Kasab could be making this all up. The only way that interrogators can tap a man's memory is to ask him. But what if the person is unwilling to spill the beans or, at least, the real ones? If only there were only a way to plug a USB cable to the back of Kasab's head and just download the experiences.

While such technology may be the stuff of science fiction, Indian government officials have announced they will employ another technique that seems to leap from the pages of a 1940s pulp novel: truth serum. Also known as narcoanalysis, administering psychoactive drugs for interrogation purposes has been around for just under a century, but it has been viewed with skepticism from the start. Indeed, the practice is banned in most democracies, and evidence obtained from such an interrogation would have a hard time making it into an American court. 

But could "truth serum" reliably extract the truth from this man and other criminal targets? We asked Alison Winter, a science historian at the University of Chicago, who has studied the origins and applications of truth serum.

What does the term "truth serum" mean?
That's a term that was used to describe the use of certain drugs, most commonly barbiturates like sodium amytal and sodium pentothal, to try to extract truthful statements from people about their past experiences.  What the term really meant was that the people who used the serum believed that it made people unable to censor themselves and they would just empty their memories into a narrative statement.

Who discovered these effects?
In the mid-1910s, Dr. Robert House was an obstetrician who noticed that the popular obstetric anesthetic drug, scopolamine, also known as twilight sleep, would put his patients into a state where they would deliver information in a way that seemed automatic.

He didn't want to use it in interrogation, for the purpose of getting people to admit to criminal acts, so this is a quite different beginning from the association we have now. At the time, he wanted to use it to provide support for claims people made about their innocence -- not their guilt.  If somebody said 'I wasn't at the crime, I was in the library but nobody saw me,' then, perhaps, this would give support for the claim, because you would think they could not lie under the drug's influence.

It was only later when other people used these drugs that they got the reputation for having the power to force people to provide information against their will.

How did they begin to be used for interrogation?
In the 1930s, there were these committees to evaluate corruption in American policing, and it first came out that police were using these drugs in interrogations to get suspects to incriminate themselves. But there's not a lot of documentation of that.

During World War II, these drugs were used in a very different way. They were the first intravenous anesthetics and were used to treat traumatized soldiers who had lost their memories or had aphasia [loss of the ability to speak or process language due to brain injury]. Doctors found that using these drugs would make it easier for people to say what happened, and this helped them feel better.

As a result, a lot of doctors who had been in the military during the war were familiar with these drugs. Sodium amytal and pentothal were no longer just used as surgical anesthetics, although that was their most common use, but they were sometimes used for this psychiatric purpose of getting people to talk.  In most cases, the drugs were not used in interrogations, but to help people talk about their memories in psychiatric consultations.  However, some of these military doctors eventually became consultants for police forces or they did psychiatric research for the government and began exploring different ways of using these drugs for interrogation.

Do experts believe they really work?
The idea of a "truth serum" has never been widely accepted. Although there have been waves of enthusiasm for the idea of a drug that can extract information reliably, there has been even more skepticism. Ever since the 1920s, many judges, psychiatrists, and scientists have rejected the idea that there is a drug that can get memories out intact. They have claimed, instead, that it makes people feel like talking, but it also puts them in a state of extreme suggestibility: people will pick up on cues about what questioners want to hear and repeat that back. This is one of the reasons that statements made under the influence of these drugs have never, as far as I know, been accepted in an American court.

After 9/11, there were discussions in the national papers about whether it's a good idea to interrogate suspects using these drugs. Every time there is a desperate need for information from people, you get speculation about whether these drugs are going to get that information. But you also get consistent warnings that the information may be less reliable than what you would get without the drugs. That skepticism was there right from the start 80 years ago.

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