Forensic evidence is admissible in Indian criminal trials mainly as the opinion of a person “specially skilled” in science or any other field. The rule is Section 39 of the Bharatiya Sakshya Adhiniyam, 2023 (BSA), formerly Section 45 of the Indian Evidence Act, 1872: when the court has to form an opinion “upon a point of foreign law or of science or art, or any other field, or as to identity of handwriting or finger impressions”, the opinions of such persons “are relevant facts and such persons are called experts”. The words “or any other field” are new; the old Section 45 covered only foreign law, science, art, handwriting and finger impressions. The report of a Government forensic laboratory can be read in evidence without calling the scientist, under Section 329 of the Bharatiya Nagarik Suraksha Sanhita, 2023 (BNSS), formerly Section 293 of the Code of Criminal Procedure (CrPC), but the court may summon the scientist, and a disputed report usually has to be proved through the person who made it.<\/p>\n\n\n\n
Admissible does not mean conclusive. An expert “is not a witness of fact and his evidence is really of an advisory character” (Ramesh Chandra Agrawal v. Regency Hospital, 2009). DNA evidence is only as good as the way the samples were collected, sealed, stored and sent: in Kattavellai @ Devakar v. State of Tamil Nadu (15 July 2025) the Supreme Court set aside a death-sentence conviction, finding among other things that the DNA evidence had been rendered “unusable”, and ordered a Chain of Custody Register in every DNA case. Narco-analysis, polygraph and brain-mapping tests cannot be forced on anyone (Selvi v. State of Karnataka, 2010).<\/p>\n\n\n\n
Forensic evidence in India at a glance<\/p>\n
Reviewed and updated by Century Law Firm, Delhi \u2013 October 2026. Statutory references are to the Acts as in force on that date. The Bharatiya Sakshya Adhiniyam, 2023, the Bharatiya Nagarik Suraksha Sanhita, 2023 and the Criminal Procedure (Identification) Act, 2022 are quoted from India Code (each as on 6 October 2025, the current versions on 23 October 2026), the Constitution from the Legislative Department’s 2026 edition, and the judgments from the Supreme Court’s own copies.<\/em><\/p>\n\n\n\n No Indian statute defines “forensic evidence”. In practice it means facts found by scientific examination of things connected with a crime: blood and body fluids, DNA, fingerprints, firearms and cartridges, poisons and drugs, documents and handwriting, and data on phones and computers. The law reaches these facts in three ways.<\/p>\n\n\n\n The Supreme Court uses the same classification. In Selvi (2010) it distinguished “personal testimony” from “material evidence such as bodily substances and other physical objects”, recording the view in Kathi Kalu Oghad that finger impressions and specimen writing “belong to the third category of material evidence which is outside the limit of ‘testimony'”. This decides whether an accused can be made to give a sample: bodily samples can be taken under the BNSS, but a test that extracts what a person knows cannot be forced.<\/p>\n\n\n\n Laboratories are organised by discipline; Himachal Pradesh’s Directorate of Forensics Services, for example, lists Biology and Serology, Chemistry and Toxicology, Documents and Photography, Physics and Ballistics, DNA, Forensic Psychology and Digital Forensics, and a Fingerprint Bureau. The table links each type to the provisions that usually apply.<\/p>\n\n\n\n Section 39(1) BSA reads: “When the Court has to form an opinion upon a point of foreign law or of science or art, or any other field, or as to identity of handwriting or finger impressions, the opinions upon that point of persons specially skilled in such foreign law, science or art, or any other field, or in questions as to identity of handwriting or finger impressions are relevant facts and such persons are called experts.”<\/p>\n\n\n\n Its three illustrations are the classic forensic questions: whether a death was caused by poison (opinions on “the symptoms produced by the poison” are relevant); whether a person was, by unsoundness of mind, incapable of knowing the nature of his act; and whether a document was written by a particular person, judged by comparison with a document “proved or admitted to have been written by A”.<\/p>\n\n\n\n Section 39(2) BSA, which was Section 45A of the Evidence Act, deals with digital material: “When in a proceeding, the court has to form an opinion on any matter relating to any information transmitted or stored in any computer resource or any other electronic or digital form, the opinion of the Examiner of Electronic Evidence referred to in section 79A of the Information Technology Act, 2000 (21 of 2000), is a relevant fact.” The Explanation adds that such an Examiner “shall be an expert”.<\/p>\n\n\n\n The firm’s comparison data, checked against the Gazette text, records one change of substance in Section 39(1): the words “or any other field” have been added, so the scope “is expanded greatly”. The old Section 45, as quoted by the Supreme Court in 2009, applied to “a point of foreign law, or of science, or art, or as to identity of hand writing or finger-impressions”. Section 45A became Section 39(2) without change of substance. Judgments decided under the Evidence Act cite Section 45; because Section 39 keeps its words and only adds to them, the firm’s reading is that those judgments remain the guide.<\/p>\n\n\n\n Three separate questions arise for every piece of forensic evidence: is it relevant, has it been proved, and how much weight should it get? Section 39 BSA answers the first: an expert’s opinion on a scientific point is a relevant fact. Proof depends on how the evidence reaches the court: through the expert’s own testimony, through a report admissible under Section 329 BNSS, or through an undisputed document under Section 330 BNSS. Weight is for the judge.<\/p>\n\n\n\n The BSA does not list qualifications. The Supreme Court, explaining the old Section 45 in Ramesh Chandra Agrawal v. Regency Hospital Ltd. (11 September 2009), a medical-negligence appeal, relied on State of H.P. v. Jai Lal: to treat a witness as an expert “it has to be shown that he has made a special study of the subject or acquired a special experience therein or in other words that he is skilled and has adequate knowledge of the subject”. The same judgment, citing a textbook, listed three further requirements for expert evidence to be admissible: “i) that the expert must be within a recognized field of expertise ii) that the evidence must be based on reliable principles, and iii) that the expert must be qualified in that discipline.” The first condition is that expert evidence is needed at all: “The test is that the matter is outside the knowledge and experience of the lay person.”<\/p>\n\n\n\n The same judgment explains the expert’s role: “It is not the province of the expert to act as Judge or Jury.” In the court’s words, “An expert is not a witness of fact and his evidence is really of an advisory character”; opinion that is “intelligible, convincing and tested becomes a factor and often an important factor for consideration along with other evidence of the case”, and its credibility “depends on the reasons stated in support of his conclusions and the data and material furnished”. The Court also quoted State (Delhi Administration) v. Pali Ram: “no expert would claim today that he could be absolutely sure that his opinion was correct”.<\/p>\n\n\n\n This is why Section 45 BSA makes the grounds of an opinion relevant: a report that sets out the samples, seals, methods and results can be tested in cross-examination; a bare conclusion is weak.<\/p>\n\n\n\n No. Daubert v. Merrell Dow Pharmaceuticals (1993) is a decision of the United States Supreme Court, which the Supreme Court of India described in Selvi (2010): it looks at whether a technique “can be and has been tested”, peer review, “its known or potential error rate”, controlling standards and scientific acceptance. Indian courts apply Section 39 BSA and the requirements in judgments such as Ramesh Chandra Agrawal, and test reliability through the grounds of the opinion and cross-examination. The earlier version of this post presented “known error rate” and “peer review” as Indian requirements and called Daubert a precedent of an unnamed “Supreme Court”; both points have been corrected.<\/p>\n\n\n\n The BNSS, in force since 1 July 2024, added several forensic steps that the CrPC did not have: a forensic expert’s visit to the scene of serious offences, video recording of searches and seizures, and a record of the “sequence of custody” of electronic devices in the police report. The infographic shows the path; the sections below explain each step.<\/p>\n\n\n\nWhat is forensic evidence, and how does Indian law classify it?<\/h2>\n\n\n\n
\n
Types of forensic evidence and the law that applies<\/h3>\n\n\n\n
Type of evidence<\/th> Examples<\/th> Main provisions<\/th><\/tr><\/thead> Biological and DNA<\/td> Blood, semen, swabs, hair, nail clippings, saliva on objects<\/td> Sections 51\u201353 and 184 BNSS (collection); Section 329(4)(e)\u2013(f) BNSS (FSL, Serologist); Section 39 BSA<\/td><\/tr> Fingerprints and other measurements<\/td> Finger, palm and foot prints, iris scans, photographs<\/td> Section 39(1) and 72(3) BSA; Section 349 BNSS; Criminal Procedure (Identification) Act, 2022; Section 329(4)(c) BNSS (Finger Print Bureau)<\/td><\/tr> Chemical and toxicological<\/td> Poison in viscera, drugs, alcohol<\/td> Section 329(4)(a) BNSS (Chemical Examiner); Section 39 BSA, illustration (a) on poison<\/td><\/tr> Ballistics and explosives<\/td> Firearms, cartridges, explosive residue<\/td> Section 329(4)(b) and (e) BNSS (Chief Controller of Explosives; FSL); Section 39 BSA<\/td><\/tr> Questioned documents<\/td> Handwriting, signatures, seals, printed notes<\/td> Sections 39, 41 and 72 BSA; Section 328 BNSS (Examiners of Questioned Documents); Section 349 BNSS<\/td><\/tr> Medical and post-mortem<\/td> Injury reports, post-mortem reports<\/td> Sections 53, 194 and 326 BNSS; Section 39 BSA<\/td><\/tr> Digital and electronic<\/td> Phone data, CCTV, e-mails, server logs<\/td> Sections 39(2) and 63 BSA; Sections 105 and 193(3) BNSS<\/td><\/tr> Psychological and psychiatric<\/td> Opinion on unsoundness of mind<\/td> Section 39 BSA, illustration (b)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Section 39 BSA (formerly Section 45 Evidence Act): opinions of experts<\/h2>\n\n\n\n
What changed from Section 45 of the Evidence Act<\/h3>\n\n\n\n
Related sections: 40, 41, 45, 55 and 72 BSA<\/h3>\n\n\n\n
BSA section (old Evidence Act section)<\/th> What it says<\/th><\/tr><\/thead> 40 (46)<\/td> Facts, “not otherwise relevant”, are relevant “if they support or are inconsistent with the opinions of experts”.<\/td><\/tr> 41 (47 and 47A)<\/td> Opinion of a person acquainted with someone’s handwriting or signature is relevant; under 41(2) the Certifying Authority’s opinion on an electronic signature is relevant.<\/td><\/tr> 45 (51)<\/td> When an opinion is relevant, “the grounds on which such opinion is based are also relevant”; “An expert may give an account of experiments performed by him”.<\/td><\/tr> 55 (60)<\/td> An opinion must be proved by the person who holds it; a published treatise can be used only if the author is dead, cannot be found, has become incapable of giving evidence, or cannot be called without unreasonable delay or expense.<\/td><\/tr> 72 (73)<\/td> The court may compare a disputed signature, writing or seal with an admitted or proved one, and may direct a person present in court to write; the section “applies also, with any necessary modifications, to finger impressions”.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n When is forensic evidence admissible, and how much weight does it carry?<\/h2>\n\n\n\n
Who counts as an expert<\/h3>\n\n\n\n
Expert opinion is advisory, not binding<\/h3>\n\n\n\n
Is the American “Daubert” test part of Indian law?<\/h3>\n\n\n\n
How forensic evidence reaches the court: the BNSS procedure<\/h2>\n\n\n\n