LLM Group 5 Criminal Law and Criminal Administration Forensic Science and Scientific Investigation of Crime 2025-26 Question Paper with Solutions

For full marks, cover: the paper gives you a choice of two out of three, so each note you write is worth about twelve and a half marks and must be a proper short essay, not four lines. All three are set out below so that you are covered whichever pair you pick. The mark is lost in the same place every year: candidates describe the technique and stop. For each note, name the statutory provision the technique operates under, give at least one decided case, and say where the technique fails. On the lie detector in particular, the description of the instrument is worth very little and Selvi is worth almost everything.

The central operation of the subject is the medico-legal autopsy, which differs from a clinical autopsy in its purpose. A clinical autopsy asks what disease killed the patient. A medico-legal autopsy asks a legal question: was this death natural, accidental, suicidal or homicidal, what caused it, when did it occur, and does the body carry marks consistent with the prosecution's account of how it was inflicted. It is performed on the requisition of the investigating agency, not at the request of the family, and the family's consent is not required.

The statutory framework the medical witness works under

The trigger is s.194 of the Bharatiya Nagarik Suraksha Sanhita, 2023. Where the officer in charge of a police station receives information that a person has committed suicide, or has been killed by another, by an animal, by machinery or by an accident, or has died in circumstances raising a reasonable suspicion that another person has committed an offence, he must give intimation to the nearest Executive Magistrate empowered to hold inquests, proceed to the body in the presence of two or more respectable inhabitants of the neighbourhood, and draw up a report of the apparent cause of death describing the wounds, fractures, bruises and other marks of injury.

For the living, the Sanhita supplies a graded set of powers. Section 51 allows a registered medical practitioner, at the request of a police officer, to examine an arrested person where there are reasonable grounds to believe the examination will afford evidence of the offence, and the Explanation is where the modern content sits: "examination" includes the examination of blood, blood stains, semen, swabs in cases of sexual offences, sputum and sweat, hair samples and finger nail clippings by the use of modern and scientific techniques including DNA profiling. Section 52 governs the examination of a person arrested for rape, and requires the report to describe the material taken for DNA profiling. Section 53 requires every arrested person to be examined. Section 184 governs the examination of the victim of rape, requires her to be sent to the practitioner within twenty-four hours, requires her consent, and requires the report to record specifically that consent was obtained.

The weight of that evidence is settled by Solanki Chimanbhai Ukabhai v. State of Gujarat, (1983) 2 SCC 174. The accused was convicted on the evidence of eyewitnesses, and the defence argued that the injuries described by the doctor were inconsistent with the manner of assault the witnesses described. The Supreme Court held that ordinarily the value of medical evidence is only corroborative: it proves that the injuries could have been caused in the manner alleged, and nothing more. The defence may legitimately use it the other way, to prove that the injuries could not possibly have been caused as alleged and so discredit the eyewitnesses. But unless the medical evidence rules out all possibility whatsoever of the injuries occurring as the eyewitnesses describe, their testimony cannot be thrown out for inconsistency with it.

Where forensic medicine is weak

The estimates the discipline produces carry margins that are wider than the confident language of a post-mortem report suggests. Time since death derived from rigor mortis, post-mortem lividity, cooling and stomach contents is affected by ambient temperature, body mass, clothing, the last meal and the manner of death, and an honest range is often measured in hours rather than minutes. Age from ossification is an approximation and becomes unreliable above about twenty-five years. The autopsy surgeon in India almost never visits the scene, so the reconstruction is done from the body alone, without the context that would discipline it. And the volume of medico-legal work carried by district hospitals means that the examination is frequently conducted by a general duty medical officer with no specialist training in the subject.

The important point for a law paper is that a sniffer alert is a screening result and not proof of anything. It generates the reasonable suspicion that justifies a search and the seizure of exhibits, and those exhibits then go to the explosives division of a Central Forensic Science Laboratory for confirmatory analysis by gas chromatography with mass spectrometry or by high performance liquid chromatography. It is the confirmatory laboratory result, spoken to by a witness who can be cross-examined, that reaches the court. The Chief Controller of Explosives is a Government scientific expert named in s.329(4)(b) BNSS, so that report has the benefit of the section.

BNSS s.176(3) is now the provision that matters most at a blast scene. On information of an offence punishable with seven years or more, the officer in charge of the police station must, from such date as the State Government notifies within five years, cause a forensic expert to visit the crime scene to collect forensic evidence and cause videography of the process. A post-blast scene is the paradigm case for the sub-section, because the evidence is microscopic residue that degrades and is destroyed by the rescue operation itself.

iii) Lie detector test

The polygraph records several physiological correlates of arousal at once: respiration through pneumograph tubes across the chest and abdomen, cardiovascular activity through a blood pressure cuff, and electrodermal activity, the galvanic skin response, through electrodes on the fingers. Questions are put in structured formats, of which the best known are the relevant and irrelevant technique, the control or comparison question test, and the guilty knowledge or concealed information test, the last of which asks about details only the offender would know rather than asking directly whether the subject is lying.

The premise, and the flaw, should be stated plainly because the marks are there. The instrument measures arousal. It does not measure deception. There is no physiological signature unique to lying. An innocent subject who is frightened of the machine, of the police, or of the consequences of an inconclusive result produces the pattern the examiner reads as deception, and a practised or unemotional subject produces the pattern read as truth. The guilty knowledge test is scientifically the most defensible of the formats because it does not depend on that inference at all, but it is usable only where the investigation has held back a detail that has not leaked.

What may be admitted is any information or material subsequently discovered with the help of a voluntarily administered test, and that comes in under s.27 of the Evidence Act, now the proviso to s.23(2) of the Bharatiya Sakshya Adhiniyam, 2023: where a fact is deposed to as discovered in consequence of information received from an accused in police custody, so much of the information as relates distinctly to the fact discovered may be proved. The Court further directed that the National Human Rights Commission's Guidelines for the Administration of Polygraph Test (Lie Detector Test) on an Accused, 2000 be strictly followed, and extended those safeguards to narco-analysis and to the brain electrical activation profile.

Amlesh Kumar v. State of Bihar, 2025 INSC 810, decided on 10 June 2025 by Karol and Varale JJ, is the current statement and was handed down ten months before this paper was sat. The Patna High Court had, on 9 November 2023, permitted narco-analysis of all the accused during investigation in a dowry matter. The Supreme Court set that order aside, holding that no individual may be forcibly subjected to such a test, that an accused has no indefeasible right to demand one either but may apply to the court which must weigh the totality of the circumstances, and that the findings of such a test cannot form the sole basis of conviction.

Conclusion. All three techniques are useful and none of them is proof. Forensic medicine tells the court what was possible and, more powerfully, what was impossible, and under Solanki Chimanbhai it displaces eyewitness testimony only when it excludes the eyewitness account altogether. The portable bomb sniffer is a screening instrument whose legal work is to generate the suspicion that justifies a search, with the confirmatory laboratory analysis carrying the evidential weight. The lie detector produces nothing admissible at all: after Selvi, and now Amlesh Kumar, the test cannot be compelled, its results are inadmissible even on consent, and the only thing that survives into the trial is a discovery made in consequence of it under the proviso to s.23(2) of the Sakshya Adhiniyam.

What a forensic science laboratory is for

A forensic science laboratory is a public scientific institution whose output is designed to be used in litigation. That single fact governs everything about it and distinguishes it from every other laboratory. A research laboratory may publish a provisional result and correct it later. A hospital laboratory answers to a clinician who can order the test again. A forensic laboratory produces a document that will be relied on to deprive a person of liberty, that will be attacked by an adversary, and that concerns a sample which frequently cannot be replaced because it was consumed in the testing or existed only once, at one place, on one day.

Everything characteristic of forensic laboratory practice follows from that. The exhibit is sealed and its seal is described. Every movement of it is recorded. The analyst notes the quantity consumed and preserves the remainder for a possible second opinion. The report states the method used, not merely the conclusion. And the analyst expects to be cross-examined on all of it.

Below the central tier, every State runs a State Forensic Science Laboratory, usually with regional and district laboratories and mobile units under it. Maharashtra's Directorate of Forensic Science Laboratories at Kalina, Mumbai, with regional laboratories at Pune, Nagpur, Aurangabad, Nashik, Amravati, Nanded and Kolhapur, is the pattern. Training and higher education were consolidated by the National Forensic Sciences University Act, 2020, which merged the Gujarat Forensic Sciences University at Gandhinagar and the Lok Nayak Jayaprakash Narayan National Institute of Criminology and Forensic Science at Rohini, Delhi, into a single university with the status of an Institution of National Importance.

The functions, division by division

How the laboratory's work reaches a court

The report of a laboratory is not evidence merely because it is scientific. It reaches the court through three provisions that must be stated accurately.

Section 39(1) of the Bharatiya Sakshya Adhiniyam, 2023 makes the opinion of a person specially skilled in science relevant where the Court has to form an opinion on a point of science, and the 2023 Adhiniyam has widened the class to "any other field". Section 39(2) is new and makes the opinion of the Examiner of Electronic Evidence under s.79A of the Information Technology Act, 2000 a relevant fact, with an Explanation deeming him an expert.

Section 329 of the Bharatiya Nagarik Suraksha Sanhita, 2023 is the provision that spares the laboratory from calling a witness in every case. A document purporting to be a report under the hand of a Government scientific expert to whom the section applies, on any matter duly submitted for examination or analysis in the course of a proceeding, may be used as evidence. The Court may summon and examine the expert, and where he cannot attend he may depute a responsible officer conversant with the facts.

The new duty to go to the scene

The most significant recent change is s.176(3) BNSS. On receipt of every information relating to an offence punishable with seven years or more, the officer in charge of the police station must, from such date as may be notified within a period of five years by the State Government, cause the forensic expert to visit the crime scene to collect forensic evidence and cause videography of the process on a mobile phone or other electronic device. Where the facility is not available, the State Government must notify the use of another State's facility until its own is developed.

This converts the laboratory from a place that receives exhibits into an agency that collects them. It is a genuine reform, because the largest single cause of failure of scientific evidence in India has always been what happened between the scene and the laboratory door rather than what happened inside the laboratory. It should be stated with its qualification, though: the duty operates from a date the State notifies, and the Sanhita gives the States five years to notify it, so it is being phased in rather than being in force everywhere from 1 July 2024.

The Court then issued binding directions for the whole country. Samples are to be packaged with proper documentation recording the FIR number and date, the section and statute involved, the details of the investigating officer and the police station, and a serial number, with the signatures of the medical professional and independent witnesses. Samples are to reach the forensic science laboratory within forty-eight hours, and any delay is to be explained in writing. A Chain of Custody Register is to be maintained recording every transfer of the sample from collection until the close of the case, signed by each person who handles it, and forming part of the trial court record. A sealed package is not to be opened, altered or resealed without the express permission of the trial court. The directions were circulated to all State Directors General of Police.

That decision followed Rahul v. State of Delhi (NCT of Delhi), 2022 LiveLaw (SC) 926, decided on 7 November 2022, the Chhawla case, where the samples had lain in police custody for about two months without any safeguard being recorded. The Supreme Court declined to act on the DNA evidence for that reason, set aside the death sentences and acquitted all three accused, observing that the failure of the investigation could not be cured by the gravity of the offence.

The second problem is that the laboratories themselves are unregulated by statute. There is no Indian legislation prescribing accreditation, proficiency testing, method validation or error-rate reporting for forensic laboratories. The DNA Technology (Use and Application) Regulation Bill, 2019, which would have created a DNA Regulatory Board with power to accredit laboratories and to lay down standards, was withdrawn from the Lok Sabha in July 2023 and has not been reintroduced. An answer that describes that Bill as law is wrong, and an answer that notes its withdrawal and draws the consequence is doing exactly what the question asks.

Conclusion. The role of a forensic science laboratory in India is to convert physical traces into an opinion that a criminal court can act upon, and its functions are organised by the kind of trace: biological, chemical, physical, documentary and digital. The law has recently strengthened that role considerably, by widening the expert provision in s.39 of the Sakshya Adhiniyam, by putting laboratory reports in evidence under s.329 of the Sanhita, and above all by requiring a forensic expert to attend the scene of every offence punishable with seven years or more under s.176(3).

Whether the strengthening produces better convictions now depends on two things the statutes do not supply: enough trained personnel to answer the new duty, and a regulatory regime for the laboratories themselves, which the withdrawal of the DNA Bill in July 2023 left India without. Kattavellai is the measure of the cost. A forty-one day unexplained gap between the swab and the laboratory door destroyed the case, and no quality of analysis inside the laboratory could have saved it.

The shift the question is about

Crime control in India has moved in one generation from a model built on human sources to one built on traces and records. The older model asked who saw it; the newer model asks what the offender left behind and what the system already knows about him. That shift is not merely technological. It has been written into the criminal law by three instruments in three years: the Criminal Procedure (Identification) Act, 2022, and the Bharatiya Nagarik Suraksha Sanhita, 2023 and Bharatiya Sakshya Adhiniyam, 2023, both in force from 1 July 2024.

The reason for the shift is stated most bluntly by the acquittals. In case after case the eyewitness has been disbelieved and the scientific material has been the only thing left, and where it too was mishandled the prosecution failed altogether. A technique-based answer should therefore begin from the proposition that these techniques are not supplements to oral evidence any longer; in serious cases they are the case.

DNA profiling is the second identification technique and is now the most powerful, because a profile can be developed from quantities of material invisible to the eye and because the discriminating power of a full profile is orders of magnitude greater than any other identification method. Its statutory hooks are in the Sanhita rather than in any dedicated statute: s.51, whose Explanation defines the examination of an arrested person to include blood, semen, swabs, sputum, sweat, hair and nail clippings by modern and scientific techniques "including DNA profiling"; s.52 for a person arrested for rape; and s.184 for the examination of the victim.

The third identification technique is the compelled measurement. The Criminal Procedure (Identification) Act, 2022, which came into force on 4 August 2022 and repealed the Identification of Prisoners Act, 1920, defines "measurements" in s.2(1)(b) to include finger impressions, palm-print and foot-print impressions, photographs, iris and retina scans, physical and biological samples and their analysis, and behavioural attributes including signatures and handwriting. Section 3 permits their taking from convicts, from persons ordered to give security for good behaviour, and from persons arrested or preventively detained. Section 5 lets a Magistrate direct any person to give measurements.

The technique-level change here is the point of collection rather than the analysis. Section 176(3) BNSS requires that, on information of any offence punishable with seven years or more, the officer in charge of the police station shall, from such date as the State Government notifies within five years, cause a forensic expert to visit the crime scene to collect forensic evidence and cause videography of the process on a mobile phone or other electronic device. Where the facility does not exist the State must notify the use of another State's. This is the single most important structural reform in the new Sanhita for this subject, because it puts a trained collector at the scene instead of leaving collection to the first constable to arrive.

Procedural techniques introduced by the 2023 codes

A set of techniques is purely procedural and is easily missed. Section 173 BNSS permits information of a cognizable offence to be given by electronic communication and irrespective of the area where the offence is committed, which is the zero first information report and the electronic first information report. Section 105 requires the search and seizure process, and the preparation of the list of seized articles, to be recorded by audio-video electronic means, preferably a mobile phone, and forwarded to the Magistrate. Section 185 carries a similar requirement for a search by a police officer. Section 193(3)(i) requires the police report to state "the sequence of custody in case of electronic device". Each of these is a technique for making the record of the investigation verifiable rather than merely assertible, and each of them exists because courts stopped believing the older records.

The cost, and the case against

The techniques described above are, taken together, a system for the permanent identification and continuous tracing of a large population, and the safeguards have not kept pace.

The retention rule is the sharpest illustration. Under s.4(2) of the Criminal Procedure (Identification) Act, 2022, records of measurements are retained in digital form for seventy-five years from the date of collection. The proviso softens this only for a narrow class: a person not previously convicted, who is released without trial, discharged or acquitted after exhausting all legal remedies, and even then the court may direct otherwise for reasons recorded in writing. A person arrested and never charged is not obviously within that proviso at all.

The constitutional standard those techniques must satisfy was set in K.S. Puttaswamy v. Union of India, (2017) 10 SCC 1, where a nine-judge Bench held that privacy is a fundamental right under Article 21 and that an invasion of it must satisfy legality, a legitimate State aim, and proportionality between the object and the means. Seventy-five years of retention of biometric data taken from a person who was arrested and never tried is difficult to defend on the proportionality limb, and the argument has not yet been authoritatively answered.

Conclusion. The modern techniques of crime control fall into five groups: identification of the person by fingerprint, DNA and compelled measurement; analysis of the traces the offender leaves; the informational technique of holding and connecting national records; the procedural techniques of videographed search, electronic first information reports and certified computer output that the 2023 codes now require; and situational and community prevention before the fact.

Indian law has adopted all five with unusual speed, and the constitutional architecture around them is thinner than the powers. The genuine advance is s.176(3) of the Sanhita, which places a trained collector at the scene of every serious offence, because that addresses the failure that has actually destroyed Indian prosecutions. The genuine gap is that seventy-five year retention under the 2022 Act has never been tested against the proportionality standard of Puttaswamy, and the Digital Personal Data Protection Act, 2023 has exempted policing from itself.

Definition

Forensic science is the application of scientific knowledge, principles and methods to questions arising in the administration of justice. The adjective comes from the Latin forensis, meaning of or belonging to the forum, the place where legal disputes were argued in Rome, and the etymology preserves the essential point: this is not a science defined by its subject matter but by its audience. Chemistry becomes forensic chemistry not because different chemistry is done but because the result is destined for a tribunal.

Paul Kirk's formulation, that the object of the discipline is to establish the individuality of physical evidence, and Richard Saferstein's, that forensic science is the application of science to the criminal and civil laws enforced by police agencies in a criminal justice system, are both worth quoting. For examination purposes the safest working definition is this: forensic science is the body of scientific disciplines applied to the detection, investigation and proof of offences, whose distinguishing feature is that its output is prepared to be tested by cross-examination.

And it is adversarial in design. Its documents are written to survive attack. That is why the sealing, the packaging, the register and the note of quantity consumed are part of the science and not administrative decoration.

The principles

The objectives are conventionally stated as five, and they are worth separating because courts treat them differently. Identification answers what a thing is, that the powder is heroin or that the stain is human blood. Individualisation answers whose it is, and is the harder and more valuable operation. Association links a person to a place, a victim or an object. Reconstruction establishes the sequence of events from the physical record. And exoneration, which is listed last and matters most in principle, eliminates the innocent, which the discipline does more reliably than it convicts.

The role of forensic evidence at trial: the Indian authorities

Forensic evidence enters an Indian trial as opinion. Section 39(1) of the Bharatiya Sakshya Adhiniyam, 2023 makes relevant the opinion of a person specially skilled in foreign law, science, art, any other field, or the identity of handwriting or finger impressions, where the Court has to form an opinion on that point, and s.45 makes the grounds of the opinion relevant as well. Everything the courts have said about weight follows from that single characterisation, and the propositions can be set out in order.

First, forensic evidence is opinion evidence and the court is not bound by it. In Pattu Rajan v. State of Tamil Nadu, (2019) 4 SCC 771, the appellants were convicted of the abduction and murder of one Santhkumar, and the identification of the recovered body was challenged on the ground that no DNA test had been done and that a superimposition test, which compares the skull with photographs of the deceased, was an improper substitute.

Third, forensic evidence is ordinarily corroborative and displaces oral testimony only when it excludes it. In Solanki Chimanbhai Ukabhai v. State of Gujarat, (1983) 2 SCC 174, the defence attacked eyewitness accounts on the footing that the medical evidence did not fit them. The Supreme Court held that the value of medical evidence is ordinarily only corroborative: it proves that the injuries could have been caused in the manner alleged and nothing more. The defence may use it affirmatively to show that the injuries could not possibly have been so caused, and thereby discredit the eyewitnesses. But unless the medical evidence rules out all possibility whatsoever of the injuries having occurred as the eyewitnesses describe, their testimony is not to be thrown out for inconsistency.

The approach should be one of caution, the reasons for the opinion must be carefully probed, all other relevant evidence must be considered, and in appropriate cases corroboration may be sought; but "in cases where the reasons for the opinion are convincing and there is no reliable evidence throwing a doubt, the uncorroborated testimony of a handwriting expert may be accepted". The reason expert opinion is fallible, he added, is not that experts are unreliable witnesses but that all human judgment is fallible, and the risk is higher where the underlying science is less perfect. The two formulations are not easy to reconcile, and the practical position is that a court will look for corroboration and will usually find that the absence of it is fatal, without treating that as a rule.

The Supreme Court acquitted, and laid down binding nationwide directions: documented packaging bearing the FIR number and date, the section and statute, the investigating officer and police station and a serial number; signature of the medical professional and independent witnesses; transmission to the laboratory within forty-eight hours with any delay explained in writing; a Chain of Custody Register recording every transfer, signed by each handler and forming part of the trial record; and no opening or resealing of a sealed package without the trial court's permission. It followed Rahul v. State of Delhi (NCT of Delhi), 2022 LiveLaw (SC) 926, where samples had lain in police custody for about two months and the Court declined to act on the DNA evidence, setting aside three death sentences.

India has no statute regulating the accreditation, method validation or proficiency testing of forensic laboratories, and the DNA Technology (Use and Application) Regulation Bill, 2019, which would have supplied a regulatory board for at least the DNA laboratories, was withdrawn from the Lok Sabha in July 2023. The second proviso to s.330 BNSS now relieves an expert of attending at all unless his report is disputed, which places the burden of triggering scrutiny on a defence that has not seen the bench notes. And the whole apparatus rests on collection by police officers whose training in it is minimal, which is the gap s.176(3) is designed to close and has not yet closed.

Conclusion. Forensic science is the application of scientific method to questions the law must answer, comparative in method, probabilistic in output and adversarial in design. Its objectives are identification, individualisation, association, reconstruction and exoneration, and its importance to the Indian criminal justice system has grown in exact proportion to the decline of oral testimony. But Indian law has never given it a privileged status.

For full marks, cover: the question names its own three limbs and you should answer them in the order given, but they are not worth the same. "What is it" is worth about four marks and should include the drug, the mechanism and the personnel. Efficacy and reliability together are worth about eight and must be answered scientifically, because the honest answer is that the technique does not do what its name claims. "Judicial procedure" is worth the remaining thirteen and means the whole Indian constitutional history: the High Court decisions that permitted it, Selvi which stopped it, the National Human Rights Commission safeguards, the section 27 exception, and Amlesh Kumar in 2025. If you are short of time, sacrifice the pharmacology and keep the case law.

The procedure is conducted by a team, ordinarily an anaesthetist who administers and monitors, a clinical or forensic psychologist who conducts the interview, and a forensic expert who records. Vital signs are monitored throughout because the drug depresses respiration and cardiac function, and the whole session is recorded on audio and video, which is a legal requirement as much as a clinical one.

Efficacy: does it produce what the investigator wants

The efficacy question must be separated from the reliability question, and candidates conflate them. Efficacy asks whether the technique produces speech at all; reliability asks whether that speech is true.

On efficacy the answer is qualified yes. Subjects in the hypnotic stage do talk, do so at length and do disclose matters they had withheld. Investigators report that the technique produces leads: the location of a weapon, the identity of a confederate, the route taken after the offence. That is why agencies have persistently sought it despite the legal difficulty.

Second, the state produces confabulation: the subject fills gaps in recollection with material that is plausible to him and reports it with the same confidence as genuine memory. The subject is not lying, which is exactly what makes it dangerous; he believes what he is saying.

Third, fantasy and actual recollection are not distinguishable in the output. A subject may narrate what he feared, imagined or was told by others as though it were experience.

Fourth, there is no validation. There is no published error rate for narco-analysis, no controlled study establishing the proportion of true to false statements it produces, and no accepted method of scoring an output. It would not survive the reliability enquiry that Ramesh Chandra Agrawal requires of any expert technique, which demands that the evidence be based on reliable principles.

The consequence, which is worth stating explicitly, is that the technique cannot even reliably exonerate. A subject who denies the offence under narco has not proved anything, because a person capable of confabulating a confession is equally capable of confabulating a denial.

Selvi and the law as it now stands

Selvi v. State of Karnataka, (2010) 7 SCC 263, decided on 5 May 2010, is the whole of the modern law, and the answer stands or falls on how completely it is set out.

The Supreme Court held, first, that the compulsory administration of narco-analysis, polygraph examination and the brain electrical activation profile violates Article 20(3). The reasoning is the point to get right. Narco-analysis produces a testimonial act: the subject is made to speak, and there is no reason to treat speech in a drug-induced state differently from answers in an ordinary interrogation. It therefore falls squarely within "to be a witness" as that expression was construed in Kathi Kalu Oghad, unlike a fingerprint or a handwriting specimen, which are material and not testimonial.

Second, the Court held that compulsory administration also violates Article 21, as an unjustified intrusion into mental privacy and personal liberty and as conduct that does not answer the requirement of a fair, just and reasonable procedure. That limb matters because it protects witnesses and suspects who are not "accused of an offence" and so cannot invoke Article 20(3) at all.

Fifth, the Court directed that the National Human Rights Commission's Guidelines for the Administration of Polygraph Test (Lie Detector Test) on an Accused, 2000 be strictly followed, and extended the same safeguards to narco-analysis and the brain electrical activation profile. Those guidelines require that the accused be given the option of the test rather than being required to take it, that he be informed of the legal, physical and emotional implications with access to a lawyer, that the consent be recorded before a Judicial Magistrate, that the lawyer be permitted to explain the implications, that the statement be recorded as a statement to the police and not as a confession, and that the whole be conducted in an independent agency's premises in the presence of a lawyer, with a full record of the physical, emotional and legal condition of the subject.

The position after Selvi, and the 2025 restatement

Amlesh Kumar v. State of Bihar, 2025 INSC 810, decided on 10 June 2025 by Karol and Varale JJ, is the current statement and predates this paper by ten months. The Patna High Court had on 9 November 2023 permitted narco-analysis of the accused persons during the investigation of a dowry-related matter. The Supreme Court set that order aside as contrary to Selvi and to Articles 20(3) and 21.

The strongest argument the other way deserves to be stated. Serious crime, particularly terrorism and organised crime, presents cases in which conventional interrogation fails and the cost of failure is high, and a technique that produces leads has obvious utility even if it produces no evidence. The answer to that argument is not that the technique is useless but that it is unreliable in a specific and dangerous way: it produces confident falsehood. An investigation that acts on a confabulated lead wastes its effort at best, and at worst builds a case against an innocent person who has implicated himself while incapable of resisting the suggestion that he should.

Conclusion. Narco-analysis is interrogation under a barbiturate infusion that suppresses inhibition, and its popular name is inaccurate because no drug compels truth. It is moderately effective at producing speech and unreliable as a source of it, because suggestibility and confabulation are features of the very state the technique induces, and because no error rate for it has ever been established.

For full marks, cover: the question is in two commands and both must be obeyed. "Enlist" means give a real list, and a list of fifteen to twenty devices arranged by the function they perform is worth about six marks on its own; a list of four is not a list. "Explain any three in detail" then means three proper expositions, each of about five hundred words, and the examiner is choosing between candidates on whether the three chosen have any law attached to them. Choose devices whose legal position you can state. The three taken below are the closed circuit television camera, the breath analyser and the comparison microscope, because each of them has a decided Indian case and a statutory provision behind it.

The list

What it does for crime control. It works in three distinct ways, and confusing them is a common error. It deters, because a visible camera raises the perceived risk of detection, which is classical situational crime prevention. It detects in progress, where the feed is actively monitored, which is rare outside major cities. And it proves after the fact, which is what it is mostly used for and which is a wholly different function requiring wholly different qualities from the installation.

Its legal position as evidence. Footage is an electronic record, and it comes in under s.63 of the Bharatiya Sakshya Adhiniyam, 2023. Sub-section (1) deems computer output to be a document admissible without proof or production of the original if the conditions in sub-section (2) are satisfied: that the output was produced by a device used regularly to store or process information for the purposes of an activity regularly carried on by the person having lawful control of it; that information of that kind was regularly fed into it in the ordinary course; that the device was operating properly throughout the material part of the period, or that any malfunction did not affect the accuracy; and that the output reproduces or is derived from the information so fed in.

The device as a control on the police themselves. Paramvir Singh Saini v. Baljit Singh, (2021) 1 SCC 184, decided on 2 December 2020, is the case worth leading with, because it turns the device around. Dealing with custodial violence, the Supreme Court directed that closed circuit television cameras with night vision and both audio and video recording be installed in every police station at all entry and exit points, the lock-up, corridors, lobbies, the reception area, verandas, the Inspector's room, the station hall, the compound and outside washrooms; that the footage be preserved for eighteen months and in no case less than a year; that the station house officer report any malfunction for immediate repair; and that the same be done in the offices of central agencies which interrogate and hold accused persons. The Court grounded the directions in Article 21.

The statutory framework. The offence is s.185 of the Motor Vehicles Act, 1988: driving or attempting to drive with alcohol exceeding thirty milligrams per hundred millilitres of blood, detected in a test by a breath analyser or in any other test including a laboratory test, or being under the influence of a drug to such an extent as to be incapable of exercising proper control. The Motor Vehicles (Amendment) Act, 2019 raised the penalty to imprisonment up to six months or a fine up to ten thousand rupees or both for a first offence, and up to two years or fifteen thousand rupees or both for a second or subsequent offence committed within three years.

Sections 203 to 205 supply the procedure. Section 203 empowers a police officer in uniform to require a driver to provide a breath specimen for a breath test where he has reasonable cause to suspect alcohol or an offence, or after an accident. Refusal without reasonable excuse permits arrest, and the person may then be required to provide a specimen for laboratory test. Section 204 governs the laboratory test, and section 205 provides that where a person is proved to have refused a breath test, the court may presume that he was under the influence.

3. The comparison microscope

What it is and how it works. A comparison microscope is two compound microscopes joined by an optical bridge so that the fields of view of both objectives are presented side by side in a single eyepiece, with a hairline dividing them. The examiner can therefore rotate and align two objects and inspect the junction between them at the same magnification and under the same lighting at the same instant. It is the fundamental instrument of every comparison discipline and, in Indian practice, it is the instrument of forensic ballistics.

What it establishes. The interior of a rifled barrel imparts to the bullet a set of longitudinal striations produced by the lands and grooves and by the individual imperfections of that barrel, which are unique to it and are reproduced, with variation, on every bullet fired through it. The breech face, firing pin, extractor and ejector similarly mark the cartridge case. The examiner test-fires the suspect weapon into a recovery tank, mounts the test bullet on one stage and the crime bullet on the other, and looks for agreement in the striation pattern across the dividing line. The same instrument compares tool marks on a forced lock, cut marks on a wire, and striations on any two surfaces.

Limits. The comparison is a judgment of sufficiency of agreement made by a human examiner, and there is no numerical threshold and no established error rate for it. A barrel changes with use and with corrosion, so the striations from an old weapon fired many times are less consistent. A soft-nosed bullet recovered from a body may be too deformed to compare at all. Smooth-bore weapons and country-made firearms, which are a very large part of the Indian firearms docket, impart no rifling marks at all, so the comparison is confined to the cartridge case where one exists. And the examiner is generally aware of which weapon the investigation favours, which is the classic condition for contextual bias.

Conclusion. The modern devices of crime control divide by function into detection, analysis, comparison, identification, surveillance, enforcement and digital examination, and they divide legally into those that produce mere suspicion and those that produce evidence. Of the three examined, the closed circuit television camera is the most widely deployed and the most fragile in court, because Arjun Panditrao makes the s.63(4) certificate indispensable and s.63(4) now demands it at every submission, while Paramvir Singh Saini has turned the same device into a control on custodial conduct under Article 21.

For full marks, cover: three commands, and the marks are weighted towards the last. Forensic biology and serology should be explained with the actual tests named, because "examination of biological evidence" is not an explanation. DNA profiling should be described as a process from swab to statistic, not as a slogan about ninety-nine point nine per cent. The admissibility limb is worth at least ten marks and must carry Indian authority on both sides of the subject: the criminal line, where Pattu Rajan, Rahul and Kattavellai now govern, and the civil and matrimonial line, where Goutam Kundu, Nandlal Wasudeo Badwaik and s.116 of the Sakshya Adhiniyam govern. Do not forget to say that India has no DNA statute.

Forensic biology

Forensic biology is the division of forensic science that examines material of biological origin, whether human, animal or plant, in order to answer a question in a legal proceeding. Its material is blood, semen, saliva, sweat, urine, faeces, vomit, hair, bone, teeth, tissue, and, on the botanical and microbial side, diatoms, pollen, spores, wood and plant fragments.

Serology: the tests, in order

Serology is the sub-discipline concerned with body fluids and their identification, species determination and grouping. Its tests are arranged in a deliberate sequence from cheap and sensitive to expensive and specific, and the order matters because the early tests must not consume or contaminate the sample the later ones need.

Blood. The presumptive tests exploit the peroxidase-like activity of haemoglobin. The Kastle-Meyer test with phenolphthalein and hydrogen peroxide gives a pink colour; leucomalachite green gives blue-green; benzidine was the classical reagent and is now avoided as a carcinogen; and luminol sprayed over a surface luminesces in darkness and reveals bloodstains that have been washed away, which makes it the tool for a cleaned scene. These are presumptive only, and vegetable peroxidases and some metal salts produce false positives, so a negative result excludes blood but a positive result does not establish it.

The confirmatory tests are the microcrystal tests: the Teichmann test, which forms haemin crystals, and the Takayama test, which forms haemochromogen crystals. These establish that the stain is blood.

Saliva is identified by the detection of amylase, and is important because it is deposited on bite marks, cigarette ends, envelope flaps and bottle rims, all of which are good sources of DNA. Hair is examined microscopically to determine whether it is human or animal, the region of the body, whether it fell naturally or was pulled, and whether the root sheath is present, because the root is what yields nuclear DNA while the shaft yields only mitochondrial DNA.

DNA profiling: the process

The scientific basis is that human beings share about ninety-nine point nine per cent of their genomic sequence, and that the variation lies in regions that do not code for proteins. Forensic profiling targets short tandem repeats, which are short sequences of two to six base pairs repeated a variable number of times at a given locus. The number of repeats at each locus is inherited, one copy from each parent, and varies widely across the population. The profile is therefore not a picture of the genome but a list of repeat counts at an agreed set of loci.

Three variants matter. Autosomal STR profiling is the standard and is the most discriminating. Y-STR profiling examines the male-specific chromosome and is used where a male contributor must be found in a mixture dominated by female material, as in most sexual assault samples, but it identifies a paternal lineage rather than an individual, so all male relatives in the male line share the profile. Mitochondrial DNA is present in many copies per cell and survives degradation, so it is used on old bone, teeth and hair shafts, but it is inherited maternally and therefore also identifies a lineage rather than a person. The amelogenin locus is routinely included to indicate sex.

Admissibility in Indian courts

There is no Indian DNA statute. The DNA Technology (Use and Application) Regulation Bill, 2019, which would have established a DNA Regulatory Board, a national DNA data bank with regional banks, and mandatory accreditation of laboratories, was introduced in the Lok Sabha on 8 July 2019 and was withdrawn in July 2023, an earlier Bill of 2018 having lapsed. Any answer that describes that Bill as law, or that describes an Indian DNA data bank as existing under statute, is wrong. DNA evidence in India therefore rests on the general law of expert opinion together with specific powers to take samples.

Admissibility itself is governed by s.39(1) of the Bharatiya Sakshya Adhiniyam, 2023, and this is where Pattu Rajan v. State of Tamil Nadu, (2019) 4 SCC 771 does its work. The appellants were convicted of the abduction and murder of one Santhkumar, and it was argued that the identification of the recovered body was bad because no DNA test had been done and a superimposition test had been used instead. The Supreme Court held that DNA evidence is itself in the nature of opinion evidence within what was then s.45 of the Evidence Act, that the court is not bound by it any more than by ballistics, fingerprint or handwriting opinion, and that the superimposition result could be accepted as part of a body of evidence when corroborated, while acknowledging that the technique is not infallible. The importance of the decision is negative: DNA gets no privileged status, and the ordinary rules about expert opinion apply to it.

The Court acquitted, and issued binding directions for the country: packaging documented with the FIR number and date, the section and statute, the investigating officer and police station and a serial number; the signatures of the medical professional and independent witnesses; delivery to the forensic science laboratory within forty-eight hours with written reasons for any delay; a Chain of Custody Register recording every transfer from collection to the close of the case, signed by each handler and forming part of the trial court record; and no opening, alteration or resealing of a sealed package without the trial court's express permission. The directions were sent to every State Director General of Police.

The civil and matrimonial line

DNA evidence has a separate Indian history in paternity disputes, and a complete answer covers it. Section 116 of the Sakshya Adhiniyam, which reproduces s.112 of the Evidence Act, makes birth during the continuance of a valid marriage, or within two hundred and eighty days of its dissolution with the mother remaining unmarried, conclusive proof of legitimacy, rebuttable only by proof of non-access.

Nandlal Wasudeo Badwaik v. Lata Nandlal Badwaik, (2014) 2 SCC 576, decided on 6 January 2014, is the counterweight and the more modern statement. A test conducted by the Central Forensic Science Laboratory at Hyderabad excluded the appellant as the biological father of the child in respect of whom maintenance had been ordered, and the question was whether the conclusive presumption in s.112 could stand against it. The Supreme Court held that where there is a conflict between a conclusive proof envisaged by law and proof based on scientific advancement accepted by the world community as correct, the latter must prevail, and that a court should be furnished with the best available science rather than left to rely on presumptions where science has an answer. The two cases are reconciled in practice by treating Goutam Kundu as governing whether the test may be ordered and Nandlal as governing what follows once it has been done.

Conclusion. Forensic biology examines biological material and asks, in order, whether it is biological, what it is, what species it came from and whose it is; serology answers the first three by a graded sequence of presumptive, confirmatory, species and grouping tests, and has been displaced at the fourth by DNA profiling. DNA profiling reads the number of short tandem repeats at an agreed set of loci and expresses the result as a random match probability. In Indian courts it is admitted as ordinary opinion evidence under s.39 of the Sakshya Adhiniyam, and Pattu Rajan is express that the court is not bound by it.

There is no DNA statute, the 2019 Bill having been withdrawn in July 2023, so the sample-taking powers come from ss.51, 52 and 184 of the Sanhita and from the Criminal Procedure (Identification) Act, 2022. What decides Indian cases now is not the profile but the custody of the sample: Rahul in 2022 and Kattavellai in 2025 both set aside death sentences because the interval between the swab and the laboratory could not be accounted for, and the forty-eight hour rule and the Chain of Custody Register laid down in Kattavellai are the operative law on this subject today.