Impact of Forensic Science on Law


Harshita Yadav, University of Petroleum & Energy Studies, Dehradun

Deepak Yadav, Law Centre-II, Faculty of Law, University of Delhi


Varun Hinge, Institute of Law, Nirma University

“Genetic Science produces truthful facts about human identity, and that establishing the truth in matters of identity is equivalent to ensuring justice” ~ Sheila Jasanoff[1]

The 20th century had rendezvous with a massive amount of technologies, starting from a light bulb to electric cars. In between the various inventions, the forensic science had become an important part in the sphere of criminal investigation. DNA referred to as deoxyribonucleic acid is unique in every human, saving the identical twins. DNA can be used by the forensic scientists to determine the criminals or parentage, if in question. In order to bring out the truth in criminal cases, suspects are administered with drug such as sodium pentothal, scopolamine and sodium amytal, this process is known as Narco-analysis. Accused are also subjected to Polygraph test popularly known as lie-detector test and brain mapping test. In this article we will discuss about the admissibility of the above-mentioned tests as an evidence in the court of law.


DNA is a helix structure which contains the genetic information of an organism. One of the significant features of DNA is that no two human beings can have same DNA structure barring the case of identical twins. DNA testing includes examination of DNA of a particular person and determines whether it can be matched to the DNA found in physical evidences such as blood, hair or semen. It is also used as tool to determine the parentage of a child.

Indian courts never doubted upon the conclusiveness and accuracy of DNA testing. Despite of that, the ocular evidence is given a preference over medical evidence in Indian Courts. The admissibility of DNA evidence depends on the accurate and proper collection, preservation and documentation as to satisfy the court that the evidence presented before the court is reliable.[2] This is so, because the evidence on the basis of DNA test pose a challenge to the fundamental rights of ‘Right to Privacy’ and ‘Right against Self-Incrimination’ enshrined under Article 21 and 20(3) respectively of the Indian Constitution.

In the case of Narayan Dutt Tiwari v. Rohit Shekhar,[3] it was held by the Supreme Court that there would be no violation of right to privacy, mentioning that the result of test would be in sealed envelope and would not be revealed to anyone.

Section 45 of the Indian Evidence Act, 1872 lays down that for forming an opinion on a foreign law, science, identify of handwriting or finger impression etc the court can rely upon the expert opinion. Further, Section 46 states that the facts stated which are not otherwise relevant, becomes relevant if they support or are inconsistent with the opinions of the experts, when such opinions are relevant.

In the case of Krishnan v. State,[4] the court considered the witnesses as the eyes and the ears of justice. Thus, in case there is disparity between ocular evidence and the opinion of a medical expert, more preference is given to the eye witnesses over the medical reports like DNA tests given by the medical experts.


Narco analysis is a term referred to as the interrogation of the suspect by administration of drugs called the ‘truth serum’ in the presence of the doctors. This causes the suspect to enter the various stages of anaesthesia. The process makes the suspect to divulge the information which otherwise is not easy to obtain in natural conscious state.

The major drawback of this technique is that some people are able to retain their ability to deceive even under the influence of the drugs while others may become extremely easy to manipulate. The statements under the influence of drugs are involuntary, the admissibility of the test still remains in question.[5] An accused cannot be convicted exclusively on the basis of narco-analysis. The test is exercised to find out supporting evidences which can be used to corroborate the relevant facts in the proceeding. Hence, a confession must be voluntary to make it admissible as evidence against the accused.

National Human Rights Commission has laid down several guidelines for conducting the test.

The test must be administered on the basis of consent of the accused and it must be obtained before a Magistrate.

The recording of the test shall be done by an independent agency and it shall be conducted in the presence of a lawyer.

The manner of information received must be recorded.[6]

The Evidence Act is completely silent on the usage of scientific process. This is raised various times by the courts but in some other cases it has been upheld in order to evaluate some complicated issues.[7] The admissibility of the narco-analysis has to be tested in accordance to the Article 20 (3) of the Indian Constitution, each time when the validity of test is in question.

The narco-analysis test came in limelight due to the infamous case of Moninder Singh Pandher & Surendra Koli v. State of U.P.[8] also known as Nithari village serial killings, where the accused undergone the test.

In Rojo George v. Deputy Superintendent of Police,[9] the court was of the opinion that in recent times the criminals had come up with sophisticated and modern techniques to commit crimes. So, there is a need for new technology for investigation such as polygraph, brain mapping and narco-analysis. Court also said that if these techniques are used in the presence of expert then it can’t be said that investigating agencies violated the fundamental human rights of any citizen of India.


Polygraph or Lie detector is a test of truth, in which by giving a sedative drug questioning is done by an expert, various indicators of the body are compared to the normal body conditions and an observation is made how a body is reacting to a stimuli. The chances to innovate a statement is less as the reasoning power of a body is made dormant by the drug. The major indicators which are observed are:

Rate of sweating

Skin resistance

Muscle contraction

Pulse rate

Heart beat

The report which is submitted by the experts are analysed by the Court and inference is given on the basis of the statement so made, it is to be noted that unless an expert is called as a witness, the opinion cannot be taken into consideration as held in “State of Maharashtra v. Damu”[10] .

Before the innovation of this technique, there was a common practice in England to get truth out from a suspect by throwing him into water or fire considering that if he is speaking truth god will save him.

NHRC has laid down some guidelines for the safeguard of Individual rights for the test:

The consent should be obtained prior to the test but if a person volunteers for the test he should be provided access to the lawyer.

The consent has to be recorded before a judicial magistrate and it has to be explained to him that the statement made is not a confession and it will not be used as an evidence against him.

The test has to be recorded by an independent authority in presence of a lawyer.[11]

There has been a prolonged debate over the admissibility and enforcement of this test, Hon’ble Supreme court of India reiterating the above guidelines in Smt. Selvi v. State of Karnataka [12]has held that:

The test can be done only with the consent of the person before a magistrate, nobody can be forced for the test

If the guidelines prescribed by NHRC has been duly followed then such results may be admissible to a limited extent in Sec 27, Indian Evidence Act.


In this test, first the person is interrogated whether he is concealing any information and after the interrogation, the person is made to sit before a computer with sensors attached to his head presenting pictures or made to hear sound to record reaction to a stimuli. The sensors attached records electrical mechanism in the brain and accounts for P300 waves which are only generated if the suspect has connection with the stimuli i.e. Picture or Sound.

The admissibility of the test is not conclusive and the report submitted needs corroboration and it is a matter which would require further consideration. The Hon’ble Supreme Court of India has ruled pre conditions for the admissibility of the scientific test under section 45 of the Evidence Act are[13]:

Is the method reliably be tested?

Potential rate of error

Whether it is accepted by the community?

Are there recognized standards that control the procedure of implementation of the technique?

In conclusion, it is necessary to devise a legislation which contains necessary regulations regarding the administration of the tests. Various guidelines must be included which need to be followed while examining the accused. Doing so, will validate the admissibility of these tests as an evidence in court of law. Furthermore, safeguarding the rights of the accused and plaintiff will become relatively easy.

[1] Sheila Jasanoff, Just Evidence: The Limits of Science in The Legal Process, 34 J. LAW, MED & ETHICS 328-332 (2006). [2] Mokshi Manhas & Gunjan Thakur, DNA Profiling: Penumbra of Criminal Law, JUS DICERE (Oct. 10, 2020, 12:39 PM), [3] (2012) 12 SCC 554. [4] (2003) 7 SCC 56. [5] Suresh Bada Math, Supreme Court Judgement on Polygraph, narco-analysis & brain mapping: A boon or a bane, IJMR (Oct. 10, 2020, 13:07 PM),,in%20the%20court%20of%20law. [6] [7] Barcelona Panda, Narco-Analysis and its Evidentiary Value in India, The Practical Lawyer (Oct. 10, 202, 13:17 PM), [8] (2011) 4 SCC 80. [9] High Court Kerala WP(C) No 6245 of 2006 (U). [10] AIR 2000 SC 1691. [11] NHRC, supra. [12] (2010) 7 SCC 263. [13] Ranitsing Brahmajeetsing Sharma v. State of Maharashtra, 2005CrLJ 2533 (SC).

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