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Magnetic resonance imaging (MRI), or nuclear magnetic resonance imaging (NMRI), is a non-invasive medical imaging technique used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it especially useful in neurological (brain), musculoskeletal, cardiovascular, and oncological (cancer) imaging.

Unlike CT, MRI uses no ionizing radiation. Rather, it uses a powerful magnetic field to align the hydrogen atoms in water in the body. Radio frequency (RF) fields are used to systematically alter the alignment of this magnetization. This causes the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to construct an image of the body.

Magnetic resonance imaging is a development of nuclear magnetic resonance. Originally, the technique was referred to as Nuclear Magnetic Resonance Imaging (NMRI). However, because the word nuclear was associated in the public mind with ionizing radiation exposure, it is generally now referred to simply as MRI. Scientists still use the term NMRI when discussing non-medical devices operating on the same principles. The term magnetic resonance tomography (MRT) is also sometimes used.

SAFETY: MRI makes use of powerful magnetic fields that, though not known to cause direct biological damage, can interfere with metallic and electromechanical devices. Additional (small) risks are presented by the radio frequency systems, components or elements of the MRI system’s operation, elements of the scanning procedure and medications that may be administered to facilitate MRI imaging.


Narco Test is the technique of administering barbiturates or certain other chemical substances, most often Pentothal Sodium, to lower a subject’s inhibitions, in the hope that the subject will more freely share information and feelings. This technique is used primarily in psychotherapy and in law enforcement for the purpose of interrogations. The term “truth drug” or “truth serum” refers to the barbiturate that is administered in Narcoanalysis.


A person is able to lie by using his imagination. It is an active process that requires mental effort. In the narco analysis test, the subject’s inhibitions and mental defenses are lowered by interfering with his nervous system by using drugs. The narco analysis test is conducted by mixing 3 g of Sodium Pentothal or Sodium Amytal dissolved in 3000 ml of distilled water. The drug depresses the central nervous system, lowers blood pressure and slows the heart rate, putting the subject into a hypnotic trance resulting in a lack of inhibition. In this state, it becomes difficult though not impossible for him to lie. In other words, whatever he speaks is considered as truth. The subject is then interrogated by the investigating agencies. The subject is made to answer specific but simple questions. The answers given are recorded both in video and audio cassettes. This is either used as evidence in court or as an aid in investigation.


The issue of using narco analysis test as a tool of interrogation in India has been widely debated. It raises serious scientific, legal, and ethical questions. Some of the main points of criticism are

Violates fundamental rights: The main provision regarding crime investigation and trial in the Indian Constitution is Art. 20(3) according to which, no person accused of any offence shall he compelled to be a witness against himself. It deals with the privilege against self-incrimination, referred to as the Right to Silence. The characteristic features of this principle are:

v   The accused is presumed to be innocent until proven guilty

v   That it is for the prosecution to establish his guilt

v   That the accused need not make any statement against his will, known as the Right to Silence

The Section161 (2) in the Code of Criminal Procedure (CrPC) also protects the Right to Silence.

  1. A narcoanalysis constitutes a forcible intrusion into subject’s mind and the subject gives answers not voluntarily but under the psychoactive effect of the drug, and thereby violates the Right to Silence.
  2. Violates human rights and is a form of torture: Arguments have been made that narco analysis constitutes mental torture. It works by inhibiting the nervous system and thus lowering the subject’s inhibitions. This is interpreted by critics as a physical violation of an individual’s mind and privacy. Thereby, it also violates the dignity of the individual. The unethical use of truth drugs is classified as a form of torture according to international law.
  3. Unreliable and is not admissible in court: Tests like narco analysis are not considered very reliable. According to prevailing medical thought, information obtained under the influence of sodium amytal or sodium pentothal can be unreliable. Subjects may mix fact and fantasy, and give false or misleading answers. Critics say that it does not increase truth-telling but merely increases talking.
  4. Suspects who are used to drug abuse may snot experience the intended effect of the barbiturate and may still remain ‘in control.’ They may give deliberately false answers but make the investigators believe he is speaking the truth.
  5. A narco analysis test report may have validity but as it includes confessions made by a semiconscious person, it must not be totally admissible in court.

In May 2010, the Supreme Court of India held that narco, polygraph and brain mapping test violate article 20(3) of the Constitution, and that they must be performed only on the prior consent of the suspect. It also held that compulsory administration of any of these techniques is an unjustified intrusion into the mental privacy of an individual. It would also ampunt to ‘cruel, inhuman or degrading treatment’ with regard to the language of evolving international human rights norms.


  1. However, it is pointed out that narcoanalysis can be a valuable aid in investigations. The police do not base their entire investigation on narcoanalysis alone. Narcoanalysis is only one among a variety of means employed.
  2. The police must be permitted to use all available methods, as long as they do not violate legal or ethical principles, as law enforcement is also important. Denying these methods can hamper the police in their investigations especially in cases such as terrorism where the defendant may use a variety of means to escape prosecution. Therefore, one has to take a balanced view.
  3. Polygraph and brain mapping are not intrusive techniques like narcoanalysis and must be permitted to be used by police in their investigations.

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