Narcoanalysis technique is the test which involves the intravenous administration of a drug that causes the subject to enter into a hypnotic trance and become less inhibited. The drug-induced hypnotic stage is useful for investigators since it makes the subject more likely to divulge information. The drug used for this test is sodium pentothal, higher quantities of which are routinely used for inducing general anaesthesia in surgical procedures. This drug is also used in the field of psychiatry since the revelations can enable the diagnosis of mental disorders.

The evolution

The use of `truth-serums’ and hypnosis is not a recent development. Earlier versions of the narcoanalysis technique utilised substances such as scopolamine and sodium amytal. The following extracts from an article trace the evolution of this technique[1]:

“With the advent of anaesthesia about a century ago, it was observed that during the induction period and particularly during the recovery interval, patients were prone to make extremely naive remarks about personal matters, which, in their normal state, would never have revealed. Probably the earliest direct attempt to utilize this phenomenon in criminal interrogation stemmed from observations of a mild type of anaesthesia commonly used in obstetrical practice during the period of about 1903-1915 and known as `Twilight sleep’.

This anaesthesia was obtained by hypodermic injection of solutions of morphine and scopolamine (also called `hyoscine’) followed by intermittent chloroform inhalations if needed. The pain relieving qualities of morphine are well known. Scopolamine appears to have the added property of blocking out memories of recent events. By the combination of these drugs in suitable dosage, morphine dulled labour pains without materially interfering with the muscular contractions of labor, while scopolamine wiped out subsequent memories of the delivery room ordeal. The technique was widely used in Europe but soon fell into disrepute among obstetricians of this country, largely due to over dosage.

During the period of extensive use of `twilight sleep’ it was a common experience that women who were under drug influence, were extremely candid and uninhibited in their statements. They often made remarks which obviously would never have been uttered when in their normal state.

Dr. Robert E. House, an observant physician practising in Ferris, Texas, believed that a drug combination which was so effective in the removal of ordinary restraints and which produced such utter candor, might be of value in obtaining factual information from persons who were thought to be lying. Dr. House’s first paper presented in 1922 suggested drug administration quite similar to the standard `twilight sleep’ procedure.

Subjects were questioned as they recovered from the light chloroform anaesthesia and gave answers which subsequently proved to be true. Altogether, Dr. House reported about half-a-dozen cases, several of which were instrumental in securing the release of convicts from State prisons, he also observed that, after returning to their normal state, these subjects had little or no recollection of what had transpired during the period of interrogation. They could not remember what questions had been asked, nor by whom; neither could they recall any answers which they had made.”

The Truth Serum

The use of the `Scopolamine’ technique led to the coining of the expression `truth serum’. With the passage of time, injections of sodium amytal came to be used for inducing subjects to talk freely, primarily in the field of psychiatry. The author cited above has further observed, Id. at p. 522:

“During World War II, this general technique of delving into a subject’s inner consciousness through the instrumentality of narcotic drugs was widely used in the treatment of war neuroses (sometimes called `Battle shock’ or `shell shock’). Fighting men who had been through terrifically disturbing experiences often times developed symptoms of amnesia, mental withdrawal, negativity, paralyses, or many other mental, nervous, and physical derangements. In most instances, these patients refused to talk about the experiences which gave rise to the difficulty, and psychiatrists were at a loss to discover the crux of the problem. To intelligently counteract such a force, it was first necessary to identify it.

Thus, the use of sedative drugs, first to analyze the source of disturbance (narcoanalysis) and later to obtain the proper frame of mind in which the patient could and would `talk out’ his difficulties, and, as they say `get them off his chest’ – and thus relieve himself (narco-synthesis or narco-therapy) – was employed with signal success. In the narcoanalysis of war neuroses a very light narcosis is most desirable. With small doses of injectable barbiturates (sodium amytal or sodium pentothal) or with light inhalations of nitrous oxide or somnoform, the subject pours out his pent-up emotions without much prodding by the interrogator.”

Test Procedure

Coming to the test procedure, when the drug (sodium pentothal) is administered intravenously, the subject ordinarily descends into anaesthesia in four stages, namely:

(i) Awake stage

(ii) Hypnotic stage

(iii) Sedative stage

(iv) Anaesthetic stage

A relatively lighter dose of sodium pentothal is injected to induce the `hypnotic stage’ and the questioning is conducted during the same. The hypnotic stage is maintained for the required period by controlling the rate of administration of the drug. The behaviour exhibited by the subject during this stage has certain specific characteristics, namely: –

  • It facilitates handling of negative emotional responses (i.e. guilt, avoidance, aggression, frustration, non-responsiveness etc.) in a positive manner.
  • It helps in rapid exploration and identification of underlying conflicts in the subject’s mind and unresolved feelings about past events.
  • It induces the subject to divulge information which would usually not be revealed in conscious awareness and it is difficult for the person to lie at this stage.
  • The reversal from this stage occurs immediately when the administration of the drug is discontinued.[2]

Personnel involved in Narcoanalysis Interview

The personnel involved in conducting a `narcoanalysis’ interview include a forensic psychologist, an anaesthesiologist, a psychiatrist, a general physician or other medical staff and a language interpreter if needed. Additionally, a videographer is required to create video-recordings of the test for subsequent scrutiny.

In India, this technique has been administered either inside forensic science laboratories or in the operation theatres of recognised hospitals. While a psychiatrist and general physician perform the preliminary function of gauging whether the subject is mentally and physically fit to undergo the test, the anaesthesiologist supervises the intravenous administration of the drug. It is the forensic psychologist who actually conducts the questioning. Since the tests are meant to aid investigation efforts, the forensic psychologist needs to closely co-operate with the investigators in order to frame appropriate questions.

The Purposes of the Technique

This technique can serve several ends. The revelations could help investigators to uncover vital evidence or to corroborate pre-existing testimonies and prosecution theories. Narcoanalysis tests have also been used to detect `malingering’ (faking of amnesia). The premise is that during the `hypnotic stage’ the subject is unable to wilfully suppress the memories associated with the relevant facts.

Narcoanalysis tests could be requested by defendants who want to prove their innocence. Demands for this test could also be made for purposes such as gauging the credibility of testimony, to refresh the memory of witnesses or to ascertain the mental capacity of persons to stand trial. Such uses can have a direct impact on the efficiency of investigations as well as the fairness of criminal trials.[3]

Limitations of the Test

It is also important to be aware of the limitations of the `narcoanalysis’ technique. It does not have an absolute success rate and there is always the possibility that the subject will not reveal any relevant information. Some studies have shown that most of the drug-induced revelations are not related to the relevant facts and they are more likely to be in the nature of inconsequential information about the subjects’ personal lives. It takes great skill on part of the interrogators to extract and identify information which could eventually prove to be useful.

While some persons are able to retain their ability to deceive even in the hypnotic state, others can become extremely suggestible to questioning. This is especially worrying, since investigators who are under pressure to deliver results could frame questions in a manner that prompts incriminatory responses. Subjects could also concoct fanciful stories in the course of the `hypnotic stage’. Since the responses of different individuals are bound to vary, there is no uniform criteria for evaluating the efficacy of the `narcoanalysis’ technique

Cases on Narco Test

  1. In an article published in 1951, C.W. Muehlberger had described a French case which attracted controversy in 1948. Raymond Cens, who had been accused of being a Nazi collaborator, appeared to have suffered an apoplectic stroke which also caused memory loss. The French Court trying the case had authorised a board of psychiatrists to conduct an examination for ascertaining the defendant’s amnesia. The narcoanalysis technique was used in the course of the examination and the defendant did not object to the same. However, the test results showed that the subject’s memory was not impaired and that he had been faking amnesia.

At the trial, testimony about these findings was admitted, thereby leading to a conviction. Subsequently, Raymond Cens filed a civil suit against the psychiatrists alleging assault and illegal search. However, it was decided that the board had used routine psychiatric procedures and since the actual physical damage to the defendant was nominal, the psychiatrists were acquitted. At the time, this case created quite a stir and the Council of the Paris Bar Association had passed a resolution against the use of drugs during interrogation.[4]

An article published in 1961[5], had surveyed some judicial precedents from the U.S.A. which dealt with the forensic uses of the narcoanalysis technique.

  • The first reference is to a decision from the State of Missouri reported as State v. Hudson, 314 Mo. 599 (1926).

In that case, the defence lawyer in a prosecution for rape attempted to rely on the expert testimony of a doctor. The doctor in turn declared that he had questioned the defendant after injecting a truth-serum and the defendant had denied his guilt while in a drug-induced state. The trial court had refused to admit the doctor’s testimony by finding it to be completely unreliable from a scientific viewpoint. The appellate court upheld the finding and made the following observation, Id. at p. 602:

“Testimony of this character – barring the sufficient fact that it cannot be classified otherwise than a self-serving declaration – is, in the present state of human knowledge, unworthy of serious consideration. We are not told from what well this serum is drawn or in what alembic its alleged truth compelling powers are distilled. Its origin is as nebulous as its effect is uncertain. …”

  • In State v. Lindemuth, 56 N.M. 237 (1952) the testimony of a psychiatrist was not admitted when he wanted to show that the answers given by a defendant while under the influence of sodium pentothal supported the defendant’s plea of innocence in a murder case. The trial court’s refusal to admit such testimony was endorsed by the appellate court, and it was noted, Id. at p. 243:

“Until the use of the drug as a means of procuring the truth from people under its influence is accorded general scientific recognition, we are unwilling to enlarge the already immense field where medical experts, apparently equally qualified, express such diametrically opposed views on the same facts and conditions, to the despair of the court reporter and the bewilderment of the fact- finder.”

  • The U.S. Supreme Court has also disapproved of the forensic uses of truth-inducing drugs in Townsend v. Sain, 372 US 293 (1963). In that case a heroin addict was arrested on the suspicion of having committed robbery and murder. While in custody he began to show severe withdrawal symptoms, following which the police officials obtained the services of a physician. In order to treat these withdrawal symptoms, the physician injected a combined dosage of 1/8 grain of Phenobarbital and 1/230 grain of Hyoscine.

Hyoscine is the same as `Scopolamine’ which has been described earlier. This dosage appeared to have a calming effect on Townsend and after the physician’s departure he promptly responded to questioning by the police and eventually made some confessional statements. The petitioner’s statements were duly recorded by a court reporter. The next day he was taken to the office of the prosecutor where he signed the transcriptions of the statements made by him on the previous day.[6]

When the case came up for trial, the counsel for the petitioner brought a motion to exclude the transcripts of the statements from the evidence. However, the trial judge denied this motion and admitted the court reporter’s transcription of the confessional statements into evidence.

Subsequently, a jury found Townsend to be guilty, thereby leading to his conviction. When the petitioner made a habeas corpus application before a Federal District Court, one of the main arguments advanced was that the fact of Scopolamine’s character as a truth-serum had not been brought out at the time of the motion to suppress the statements or even at the trial before the State Court. The Federal District Court denied the habeas corpus petition without a plenary evidentiary hearing, and this decision was affirmed by the Court of Appeals. Hence, the matter came before the U.S. Supreme Court. In an opinion authored by Earl Warren, C.J. the Supreme Court held that the Federal District Court had erred in denying a writ of habeas corpus without giving a plenary evidentiary hearing to examine the voluntariness of the confessional statements.

Both the majority opinion as well as the dissenting opinion (Stewart, J.) concurred on the finding that a confession induced by the administration of drugs is constitutionally inadmissible in a criminal trial.

Admissibility in India

In India, the Supreme court, considered the question of its admissibility in detail in the case of ‘Selvi v. State of Karnataka, (2010)’. The court said, that

“It is quite evident that the narcoanalysis technique involves a testimonial act. A subject is encouraged to speak in a drug-induced state, and there is no reason why such an act should be treated any differently from verbal answers during an ordinary interrogation. Therefore, the court held that there is no obstruction to the proposition that the compulsory administration of the narcoanalysis technique amounts to `testimonial compulsion’ and thereby triggers the protection of Article 20(3).”

While concluding the judgment, the court held-

  • The compulsory administration of the test violates the `right against self- incrimination’. This is because the underlying rationale of the said right is to ensure the reliability as well as voluntariness of statements that are admitted as evidence. Supreme Court has recognised that the protective scope of Article 20(3) extends to the investigative stage in criminal cases and when read with Section 161(2) of the Code of Criminal Procedure, 1973 it protects accused persons, suspects as well as witnesses who are examined during an investigation.

The test results cannot be admitted in evidence if they have been obtained through the use of compulsion.

  • Article 20(3) protects an individual’s choice between speaking and remaining silent, irrespective of whether the subsequent testimony proves to be inculpatory or exculpatory.
  • Forcing an individual to undergo the test violates the standard of `substantive due process’ which is required for restraining personal liberty. Such a violation will occur irrespective of whether these techniques are forcibly administered during the course of an investigation or for any other purpose since the test results could also expose a person to adverse consequences of a non-penal nature.
  • The compulsory administration of technique is an unjustified intrusion into the mental privacy of an individual. It would also amount to `cruel, inhuman or degrading treatment’ with regard to the language of evolving international human rights norms.
  • Furthermore, placing reliance on the results gathered from this test comes into conflict with the `right to fair trial’. Invocations of a compelling public interest cannot justify the dilution of constitutional rights such as the `right against self-incrimination’.
  • No individual should be forcibly subjected to test in question, whether in the context of investigation in criminal cases or otherwise. Doing so would amount to an unwarranted intrusion into personal liberty.
  • However, the court left room for the voluntary administration of the test in the context of criminal justice, provided that certain safeguards are in place.
  • Even when the subject has given consent to undergo test, the test results by themselves cannot be admitted as evidence because the subject does not exercise conscious control over the responses during the administration of the test.
  • However, any information or material that is subsequently discovered with the help of voluntary administered test results can be admitted, in accordance with Section 27 of the Evidence Act, 1872.
  • THE NATIONAL HUMAN RIGHTS COMMISSION HAD PUBLISHED `GUIDELINES FOR THE ADMINISTRATION OF POLYGRAPH TEST (LIE DETECTOR TEST) ON AN ACCUSED’ IN 2000. These guidelines should be strictly adhered to and similar safeguards should be adopted for conducting the `Narcoanalysis technique’.

The text of these guidelines has been reproduced below:

(i) No Lie Detector Tests should be administered except on the basis of consent of the accused. An option should be given to the accused whether he wishes to avail such test.

(ii) If the accused volunteers for a Lie Detector Test, he should be given access to a lawyer and the physical, emotional and legal implication of such a test should be explained to him by the police and his lawyer.

(iii) The consent should be recorded before a Judicial Magistrate.

(iv) During the hearing before the Magistrate, the person alleged to have agreed should be duly represented by a lawyer.

(v) At the hearing, the person in question should also be told in clear terms that the statement that is made shall not be a `confessional’ statement to the Magistrate but will have the status of a statement made to the police.

(vi) The Magistrate shall consider all factors relating to the detention including the length of detention and the nature of the interrogation.

(vii) The actual recording of the Lie Detector Test shall be done by an independent agency (such as a hospital) and conducted in the presence of a lawyer.

(viii) A full medical and factual narration of the manner of the information received must be taken on record.


Selvi v. State of Karnataka, (2010)

(References in the article, as quoted by court in the judgment)

[1] C.W. Muehlberger, `Interrogation under Drug-influence: The so-called Truth serum technique’, 42(4) The Journal of Criminal Law, Criminology and Police Science 513-528 (Nov- Dec. 1951) at pp. 513-514.

[2] Laboratory Procedure Manual – Forensic Narco-Analysis (Directorate of Forensic Science, Ministry of Home Affairs, Government of India, New Delhi – 2005); Also see John M. Macdonald, `Truth Serum’, 46(2) The Journal of Criminal Law, Criminology and Police Science 259-263 (Jul.-Aug. 1955)

[3] George H. Dession, Lawrence Z. Freedman, Richard C. Donnelly and Frederick G. Redlich, `Drug-Induced revelation and criminal investigation’, 62 Yale Law Journal 315-347 (February 1953)

[4] C.W. Muehlberger (1951) at p. 527; The Raymond Cens case has also been discussed in the following article: J.P. Gagnieur, `The Judicial use of Psychonarcosis in France’, 40(3) Journal of Criminal Law and Criminology 370-380 (Sept.-Oct. 1949

[5] Andre A. Moenssens, `Narcoanalysis in Law Enforcement’, 52(4) The Journal of Criminal Law, Criminology and Police Science 453-458 (Nov.- Dec. 1961)

[6] The facts of this case have also been discussed in: Charles E. Sheedy, `Narcointerrogation of a Criminal Suspect’, 50(2) The Journal of Criminal Law, Criminology and Police Science 118-123 (July- Aug 1959) at pp. 118-119