Narco-Analysis

In one line

The drug removes the ability to withhold, not the ability to invent.

In the wording a student can write in an exam: narco-analysis is an interrogation technique in which a psychoactive drug, in Indian practice sodium pentothal, is administered intravenously under controlled conditions to bring the subject to a hypnotic state in which his reasoning power and his capacity to withhold information are suppressed, and he is then questioned; its premise is that a person in that state cannot lie, and its flaw is that the drug acts on inhibition and not on truth, so the state induced is one of suggestibility in which the content of the answers is shaped by the questions and the subject may confabulate; it may not be administered without consent, and even with consent the results are not admissible in evidence, though information subsequently discovered with their help may be proved.

What is done

The drug. Sodium pentothal, a barbiturate also used in higher doses to induce general anaesthesia. It is given intravenously by slow infusion.

The state induced. Between full consciousness and anaesthesia, a hypnotic state in which the subject is drowsy, disinhibited and highly suggestible. The dose must be maintained within a narrow range: too little and nothing changes, too much and the subject is unconscious.

Who is present. In Indian practice an anaesthetist, a psychiatrist or psychologist, a forensic expert to conduct the questioning, and recording equipment.

The questioning. Structured, and recorded on audio and video, which is essential because what is said in the state is often unclear and the recording is the only record.

Why it does not work as claimed

The drug acts on inhibition. It suppresses the capacity to withhold, not the capacity to invent. A subject who wishes to lie may still do so, less carefully.

The state is one of suggestibility. The subject accepts and elaborates suggestions embedded in the questions, so the content of the answers is powerfully shaped by the questioner. Two examiners asking different questions get different accounts from the same subject.

Confabulation. The subject produces plausible material that he has not experienced, without any intention to deceive, and cannot distinguish it from memory afterwards.

Consciousness is not absent. The subject retains a degree of awareness and can resist.

And there is no validation. No published body of work establishes an error rate for the technique in the sense a court would need.

What its supporters say, and it should be stated fairly. Subjects in the hypnotic state do speak at length and do disclose matters previously withheld, and investigating agencies have reported operational value in the leads obtained. That is a claim about leads, and it is consistent with everything above: the technique may point an investigation somewhere useful while remaining worthless as proof.