Sodium pentothal is used in something called a narco test in India. Why not any other drug?


I think its use has been replaced by something else by now in most parts of the world, but why do they choose the drugs they choose for “truth serum” purposes?
(The results of a narco test aren’t admissible in court)

In: 1

If you inject someone with enough sodium pentothal they will initially become unconscious as the sodium pentothal turns most of their brain off.

As the sodium pentothal wears off, the person’s brain begins to slowly turn back on. The first parts that turn on are the parts of your brain responsible for the basic functions involved in being awake, while the last parts that turn on are the parts responsible for thinking. During that turn back on period, there is a twilight phase where the person is awake enough to respond to simple questions, but not so awake that they are capable of actively trying to deceive you.

Because they can’t really lie, people have a high chance of responding truthfully to questions they are asked. Its not a 100% thing and there are several common issues:

1) People often babble incoherently and may continue babbling in response to a question.

2) People in that state are easily confused and may answer a different question than what they asked.

3) Sodium Pentothal interferes with memory, so people may not remember the answer to the question but, nonetheless, try to answer without indicating their inability to remember the correct answer.

In other words, the mechanism by which sodium pentothal causes people to give truthful answers is by disrupting brain activity. One of the other consequences of disrupting someone’s brain activity is that, due to the effects of the drug, the person temporarily thinks the answer they gave is correct, even though its really nonsense.

That doesn’t mean its a completely useless technique, but its really only useful for confirming things that you already have a pretty good idea about. IE, you strongly believe that Joe is your subject’s friend. When you ask them who their friend is, they say Joe. The likelihood of their friend being Joe just went up substantially.

Conversely, if they say their friend is named Steve, but you have no idea who Steve is, then that doesn’t mean much. It could be that their friend actually is Steve and not Joe. It could also be that Steve is just the first name that came to their mind and, in their drug induced twilight state, they assumed that meant that Steve was their friend when, in fact, Joe is.

The idea is that sodium pentothal *supposedly* makes it difficult for you to lie. It is a barbituate, which suppresses the part of the brain responsible for higher level thinking and inhibition. In theory this would make it more difficult to lie.

> I think its use has been replaced by something else by now in most parts of the world, but why do they choose the drugs they choose for “truth serum” purposes?

The answer to this question is, no, it has not been replaced. It has been *discarded.* Like you say, even in countries that still use it, it’s often not admissible in court. In reality, ***no drug has ever been scientifically proven to aid in forcing somebody to tell the truth.*** There have been studies involving these drugs, but there are doubts about whether they are sufficiently free of bias or noise to use as genuine evidence. Another problem with this drug and others like it is while it may, or again, may not, aid in getting a suspect to talk, it also very well make it easy for interrogators to mess with people’s heads and implant or fabricate memories, which makes it potentially subject to prosecutorial abuse. If you want a truth serum, you need one which is:

1. safe
2. effective at getting the truth from suspects
3. resistant to tampering by interrogators, and
4. ethical

We don’t have anything which has been scientifically shown to meet the requirements of 2 and 3, and it’s doubtful that any kind of truth serum satisfies requirement 4, at least if the right to not incriminate yourself is part of your country’s legal doctrine.

There is no such thing as a truth serum. You can’t force people to tell the truth. There’s no “lying center” in the brain that you can selectively switch off.

Lying is harder than telling the truth. The truth doesn’t require you to make stuff up. Making stuff up isn’t so hard, but making it believable and coherent is. The truth is always self-consistent. You don’t have to make all the pieces fit when telling the truth – they already fit by default. But when constructing a lie, you have to think hard to make sure you don’t contradict yourself, or any facts that the other person already knows. And with every question you are asked, you have to consult your memory about the lies you’ve told so far. Also, you have to suppress the urge to simply answer the question truthfully, which is what people are naturally inclined to do.

In short, lying requires all this hard thinking and self-control. What putative “truth serums” often try to do is shut down the parts of the brain that are necessary to do that. Lower inhibitions and suppress higher cognitive functions. In theory, that could cause a person to tell the truth simply because they lack the necessary functions for lying. However, when you shut down all these things, it does a lot more than just make it harder for the person to lie. By suppressing the person’s self-control, they can’t inhibit themselves from responding to any impulse that presents itself. They will likely find it very hard to focus on your questions and be very distractible. As in, if they see you wearing a hat, they might comment on that with the first thing that pops into their head, rather than answer your question. This impulsiveness may also interfere with their truth-telling. Without proper inhibition, thinking and speech can become very associative. Meaning they might start off answering your question, but then what they’re saying triggers all kinds of associations and that derails their story in a completely irrelevant direction. Like “Johnny? Yeah I saw him at the bar. I like bars, they serve nice drinks. I drank a whisky once that had a snake in it. I hate snakes….” and so on.

Worse, when you remove a person’s inhibitions, they become very suggestible and their memories become very open to fabrication. So even if they seem to be confessing to something or giving you relevant information, they might simply be spinning a completely made-up story in response to what you prompted them with. In other words, they will still be lying – just not deliberately.

At best, these kinds of interrogation techniques can be used as leads for further investigation. For instance, if a person says they buried the bodies in a specific location, you can go search for them there. But you can’t take the statement itself as any sort of reliable confession. Besides which of course it is ethically questionable to be subjecting people to this sort of treatment – especially suspects who have not been proven guilty of any crime.

Sodium pentothal, also known as sodium thiopental, is a fast-acting barbiturate that is sometimes used as an anesthetic or sedative. In India, it has been used in the past for something called a “narco test,” which is a type of interrogation technique where a person is injected with the drug and questioned while under its effects.
The use of sodium pentothal for narco testing is controversial and has been criticized by human rights organizations and legal experts. There are concerns about the reliability and validity of information obtained through narco testing, as the effects of the drug can alter a person’s memory and perception of events.
As for why sodium pentothal specifically is used in narco testing in India, it may be due to its fast-acting nature and ability to quickly induce a state of relaxation and sedation. Other drugs may also be used for similar purposes in other countries or contexts, but the use of any drug for interrogation or investigation purposes raises ethical and legal questions. It is generally considered preferable to obtain information through legal and ethical means, such as voluntary confessions, corroborating evidence, and eyewitness accounts.

Narco refers to the sleep inducing and/or hypnotic state induced by the drug. The idea is people may be more prone to revealing truth/secrets while half baked on the drug.