What does BNSS 2023 Section 176(3) require for physical evidence?

BNSS 2023 Section 176(3), which came into force on 1 July 2024 replacing CrPC Section 176, makes a forensic-expert visit to the scene mandatory for every offence punishable with imprisonment of seven years or more. The forensic expert collects and packages the evidence, prepares an FSL report, and the report becomes part of the chargesheet. Section 105 separately requires audio-video recording of the search and seizure, and Section 348 carries forward the IEA Section 73 power allowing courts to direct accused persons to give specimens of handwriting, signature, fingerprints or voice. Together these provisions make scientific evidence-gathering a statutory step in every serious case.

What constitutes a broken chain of custody, and what is the legal consequence?

A chain of custody is broken when there is any unexplained gap in the record of who held the exhibit between seizure and production in court. Typical breaks are: missing Malkhana register entry at the police station, broken or mismatched seal at the FSL, a date gap between despatch and FSL receipt, an absent BSA 2023 Section 63 (formerly IEA Section 65B) certificate for an electronic record like CCTV footage or an instrument printout, and a missing signature at any transfer node. The legal consequence is that the BSA 2023 Section 39 expert opinion can be discarded because the court cannot satisfy itself that the sample examined is the sample seized. Anvar P.V. v. P.K. Basheer (2014) and Arjun Panditrao Khotkar v. Kailash Kushanrao Gorantyal (2020) made the Section 65B / Section 63 certificate mandatory; State of Maharashtra v. Damu (2000) and Mukesh v. State (2017) show how an intact chain carries a circumstantial case across the conviction threshold.

Physical Evidence: Nature, Types, Collection and Chain of Custody

UGC-NET Paper 2 Unit I notes on physical evidence: nature, types, search methods, collection, preservation and chain of custody under BNSS 2023 + BSA 2023.

Last updated: 18 May 2026

Physical evidence is the second bullet of Unit I in the UGC-NET Forensic Science syllabus and arguably the most heavily examined one across years. NTA splits it into seven recall blocks: what physical evidence is (nature), how it is classified (types), how the scene is searched, how each class is collected, how it is preserved, how it is packaged and forwarded to the laboratory, and how the chain of custody is held intact under the Bharatiya Sakshya Adhiniyam 2023. Every block has both a textbook answer and a statutory hook, and NTA tests both sides.

Treat this topic as one principle (Locard) plus one workflow (search, collect, preserve, package, forward, hand over). The principle anchors the science. The workflow anchors the law: BNSS 2023 Section 176(3) sends the FSL to the scene, Section 105 videographs the search and seizure, Section 348 brings the analyst's report into evidence, and BSA 2023 Sections 22, 39 and 56 to 63 govern relevance, expert opinion and the electronic-evidence certificate. A break anywhere in the chain breaks the case, which is why Indian appellate courts spend more time on custody than on chromatography.

Key terms

Physical evidence: Any tangible object, mark or trace, biological, chemical or physical, that can establish a fact in issue in a criminal or civil proceeding by scientific examination.
Locard's exchange principle: Edmond Locard (1910, Lyon): when two objects come into contact, there is a mutual transfer of material between them. The basis of all trace-evidence work.
Individual characteristics: Features that allow an item to be associated with one specific source to the practical exclusion of all others, for example fingerprint ridge minutiae, DNA STR profile, striations on a fired bullet.
Class characteristics: Features common to a group of items that allow categorisation but not single-source identification, for example shoe brand and size, ABO blood group, fibre type.
Transient evidence: Short-lived evidence that changes or disappears quickly: temperature, odour, blood drying, footprints in snow. Must be documented first.
Conditional evidence: Evidence produced by an event and dependent on the conditions, for example state of doors and windows, position of body, lividity pattern.
Pattern evidence: Two-dimensional or three-dimensional patterns: bloodstain spatter, glass fracture, tool marks, tyre marks, fire burn patterns, gunshot residue distribution.
Transfer evidence: Material exchanged between people, objects and locations: hair, fibres, paint, glass fragments, soil, biological fluids. Direct application of Locard.
Control sample: A known reference sample collected from a substrate near the questioned stain (unstained cloth, soil from an undisturbed area) to rule out contamination from the substrate itself.
Chain of custody: The continuous, documented record of every person who handled the exhibit from seizure to courtroom, with date, time, purpose and signature at each transfer.
Tamper-evident seal: Sealed packaging that visibly shows interference, for example wax seal with case number, numbered security tag, holographic strip. Required for all forwarded exhibits.
Form 21 (viscera): Standard Indian forwarding form for viscera and biological samples sent to the FSL toxicology division, listing exhibits, preservatives, FIR number, autopsy surgeon and seal impressions.

Nature of physical evidence and Locard's exchange principle

Mute witness, mutual transfer, the only evidence that does not lie.

Physical evidence is any tangible material recovered from a scene, a victim or a suspect that can shed light on a fact in issue through scientific examination. Paul L. Kirk called it the "mute witness" that does not forget, does not get confused, does not get intimidated and does not lie, in contrast to eyewitness testimony, which Indian appellate jurisprudence treats as inherently fallible. The Supreme Court reaffirmed this preference in State of Maharashtra v. Damu (2000), where circumstantial physical evidence (recovery of the victim's belongings under Section 27 of the Indian Evidence Act, now BSA 2023 Section 23) tied the chain together, and in Mukesh v. State (NCT of Delhi) (2017), the Nirbhaya appeal, where DNA, dental and bitemark evidence carried weight that no single eyewitness account could.

The scientific bedrock is Edmond Locard's exchange principle, formulated around 1910 at the Lyon police laboratory: "every contact leaves a trace". When a suspect touches a victim, fibres, hair, skin cells, sweat, saliva, blood, soil, paint, glass fragments and gunshot residue move in both directions. The principle is the reason a forensic examiner collects control samples, reference samples and the substrate alongside the questioned stain, and the reason an integrated CSI kit (as supplied by the Directorate of Forensic Science Services, DFSS, New Delhi, to State SFSLs) carries swabs, tweezers, tape lifts and sterile containers for each transfer class. The Indian CSI doctrine adds three working corollaries: physical evidence is created at the moment of contact, degraded by every subsequent action (weather, footfall, well-meaning bystanders), and only as good as its documentation.

Classification of physical evidence

Individual versus class; transient, conditional, pattern, transfer; biological, chemical, physical.

NTA examines physical-evidence classification along three axes, and the MCQ correct answer depends on which axis the stem invokes.

Axis 1, evidential value. Individual characteristics allow association with a single source: fingerprint minutiae (ridge endings, bifurcations), DNA STR profile across the CODIS-style 13 to 20 loci panel used by the CFSL DNA division and CDFD Hyderabad, striations on a fired bullet from a single barrel, handwriting from a single writer, and tool-mark striations on a single tool edge. Class characteristics allow categorisation only: ABO blood group, shoe brand and size, paint colour and resin type, fibre polymer (cotton, polyester, nylon), glass refractive index, fired-cartridge calibre. Class evidence narrows the suspect pool; individual evidence identifies the source.

Axis 2, behaviour at the scene. Transient evidence is short-lived (odour of phosphine, ambient temperature, blood that dries from glossy to matt, ice melt around a body) and must be documented first or it is lost. Conditional evidence captures the event state (door bolt position, headlight switch state in a road-traffic-accident vehicle, lividity pattern on a body before it is shifted). Pattern evidence is geometric (bloodstain spatter direction, glass radial and concentric fracture, gunshot-residue tattoo and powder distribution, tyre mark spacing, tool-mark impression shape). Transfer evidence is the direct Locard product (hair, fibre, paint, glass, soil, body fluid, gunshot residue on hands).

Axis 3, nature of the material. Biological evidence covers blood, semen, saliva, hair, bone, viscera, tissue, urine, faeces, nails and the bacterial-toxin / botulinum / Vibrio cholerae specimens forwarded to the Microbial Toxicology Division at CFSL Hyderabad. Chemical evidence covers drugs and poisons (NDPS exhibits, pesticides, heavy metals, alcohol, arson accelerants, explosives, dyes, inks).

Search methods at the crime scene

Spiral, grid, strip or lane, zone or quadrant, wheel.

Five search patterns dominate the Indian CSI textbooks and the NTA paper. The choice depends on the size of the scene, the number of searchers and the terrain.

Spiral search. A single searcher walks in a spiral from a fixed point. Spiral inward starts at the perimeter and converges on a centre target (typically the body in a homicide). Spiral outward starts at the centre and works outward to the perimeter. Inward spiral preserves the centre, outward spiral preserves the perimeter; both fail in cluttered indoor scenes. Best for small open scenes or the scene under a body once the body is moved.

Grid search. Two passes at right angles: first a strip search north-south, then the same area re-searched east-west. Slow but the most thorough; finds the second-pass evidence the first pass missed. Standard for outdoor scenes where time allows, for example open-field homicide and aircraft-crash debris recovery as performed by DGCA / AAIB alongside the State SFSL.

Strip or lane search. The scene is divided into parallel strips; searchers walk each strip in turn. Faster than grid (single pass) but misses what a perpendicular pass would catch. Used for railway-track scenes, road verges, and the perimeter of an explosion site coordinated by the NSG Bomb Data Centre and the NIA.

Zone or quadrant search. The scene is divided into zones (rooms in a house, quadrants in a hall), and a searcher or team is assigned per zone. Standard indoor method, used by Delhi Police Crime Branch in flat and apartment scenes and by State SFSL mobile units sent under BNSS 2023 Section 176(3).

Wheel or ray search. A small circular scene is searched along rays radiating from a centre. Limited utility because spacing widens away from the centre; used mainly for clearly circular scenes (a single bomb crater).

A sixth pattern, the link search, is taught in some Indian curricula: the investigator follows logical connections between items (body, weapon, point of entry) rather than a geometric pattern. It is more a state of mind than a method.

Collection and preservation by evidence type

Paper not plastic for biologicals; glass and firearms separately; always a control sample.

Collection rules are evidence-class-specific, and NTA loves the small operational details.

Biological evidence (blood, semen, saliva, hair, tissue). Wet stains are dried at room temperature, away from direct sunlight and heat, then packed in paper bags or breathable cotton cloth, never plastic. Plastic traps moisture, encourages bacterial and fungal growth, and destroys DNA within hours. Liquid blood for grouping and DNA is drawn into an EDTA vacutainer (purple cap, 5 ml) and refrigerated at 4 degrees Celsius; for alcohol estimation, sodium fluoride and potassium oxalate (grey cap) is used to prevent fermentation. Swabs of dried stains are taken with sterile distilled-water-moistened cotton swabs, air-dried, and placed in paper sleeves. Hair is collected with clean tweezers (root preserved for nuclear DNA, shaft for mitochondrial DNA at CDFD Hyderabad) and packed in folded paper bindles inside paper envelopes. A control sample of unstained substrate is always taken from the same surface.

Viscera for toxicology. Stomach with contents, small intestine first 30 cm with contents, half each of liver and kidney, blood, urine, and where relevant brain, lung and skin around an injection mark, are placed in wide-mouthed glass jars with saturated common salt (sodium chloride) as preservative, except blood (NaF or sodium fluoride) and the specimen for alcohol (NaF). Each jar is sealed, labelled, and forwarded with Form 21 to the FSL toxicology division. Where insecticide poisoning is suspected, rectified spirit must not be used because it interferes with the analysis.

Chemical evidence. Suspected drugs under the NDPS Act are weighed, sampled (representative portions per the standing instruction of the Narcotics Control Bureau), packed in heat-sealed polythene with a moisture-resistant outer wrap, sealed with the seizing officer's seal, and forwarded with the NDPS forwarding memo. Arson debris is packed in

Packaging, sealing and forwarding under BNSS 2023

Tamper-evident seal, forwarding memo, Section 105 videograph, FSL routing.

Packaging is a legal act, not a logistical one. Each exhibit is packed in its own container, the container is closed, the closure is sealed with the seizing officer's brass seal in molten wax or a numbered tamper-evident security tag, and the seal impression is recorded on the seizure memo, the panchnama and the forwarding memo. A duplicate seal impression on a separate paper accompanies the parcel so the FSL can verify the seal is intact and matches the impression.

The BNSS 2023 Section 105 requires audio-video recording of the search and seizure on any electronic device available to the police, with copies preserved for the Magistrate and the accused. This is the statutory upgrade over the old CrPC Section 100 and brings the search itself into the chain-of-custody record. BNSS 2023 Section 176(3) mandates an FSL visit for offences carrying seven years' imprisonment or more, with the seizure now reflected in the FSL examination report attached to the chargesheet. BNSS 2023 Section 348 carries forward the IEA Section 73 power, allowing the court to direct the accused to give specimens of handwriting, signature, finger impressions or voice for comparison.

The forwarding memo carries the FIR number, the case sections, the list of exhibits with seal numbers, the examination sought (DNA profiling, narcotics identification, toxicology, ballistics, fingerprint comparison, document examination), the laboratory addressed (CFSL Hyderabad for narcotics, DNA and toxicology; CFSL Chandigarh for ballistics and questioned documents; CFSL Kolkata for chemistry and serology; CFSL Pune for general chemistry and biology; CFSL New Delhi as the apex coordinating laboratory; CFSL Bhopal, Guwahati under DFSS expansion; the appropriate State SFSL for first-line work; RFSL for regional support), and the despatch mode (registered post, special messenger, sealed despatch).

Indian institutional anchor: the Directorate of Forensic Science Services (DFSS) under the Ministry of Home Affairs administers the central CFSL network and issues the

Chain of custody under the BSA 2023 and break-in-chain case law

Continuous, documented, contemporaneous; one break and the exhibit is excluded.

Chain of custody is the unbroken paper trail showing every person who held the exhibit from the moment of seizure to its production in court. At each transfer, the record names the person handing over, the person receiving, the date and time, the location, the purpose of the transfer, the seal status, and the signature of both parties. The minimum nodes for a typical exhibit are: seizing officer at the scene, investigating officer, station house Malkhana with Malkhana register entry, despatcher to the FSL, FSL receipt clerk, analyst, return to despatch, return to police, production in court. Each node is a row in the register; gaps are fatal.

The Bharatiya Sakshya Adhiniyam 2023 frames the chain in three statutory provisions. Section 22 (relevancy of facts forming part of the same transaction) puts the chain of seizure within the res gestae of the offence. Section 39 (opinion of experts) makes the FSL report admissible only if the chain is intact, because the expert's opinion presupposes that the sample examined is the sample seized. Sections 56 to 63 govern electronic records: Section 56 makes electronic records primary evidence in the form printed, Section 61 prevents denial of admissibility solely because the record is electronic, and Section 63 (carrying forward IEA Section 65B) requires the electronic-evidence certificate for any computer-generated output, including the videographed search under BNSS Section 105 and the FSL's analytical output (LC-MS chromatograms, DNA electropherograms, fingerprint AFIS hit lists).

Indian appellate jurisprudence on broken chains is rich. In State of Maharashtra v. Damu (2000)

PYQ pointers

NTA repeatedly tests: Locard's principle attribution to Edmond Locard, 1910, Lyon; the difference between individual and class characteristics; the five standard search patterns with the spiral inward / outward distinction; paper not plastic for biological evidence and the reason (moisture and DNA degradation); EDTA vacutainer for DNA blood, NaF + potassium oxalate for alcohol blood, saturated NaCl for viscera; BNSS 2023 Section 176(3) mandatory FSL visit threshold (seven years); BSA 2023 Section 63 (formerly IEA 65B) electronic-evidence certificate for any secondary electronic output; and the Ritesh Sinha 2019 style proposition that BSA 2023 Section 348 (formerly IEA 73) covers compelled specimens. For verified year-tagged PYQs, cross-reference NTA's published past-paper PDFs; this topic deliberately avoids citing unconfirmed years.

MCQ takeaways

Locard's exchange principle: Edmond Locard, Lyon, 1910. "Every contact leaves a trace." The basis of all trace evidence.Individual characteristic = fingerprint minutiae, DNA STR, bullet striations. Class characteristic = ABO group, shoe size, fibre polymer.Search patterns: spiral (single searcher, inward or outward), grid (two-pass, most thorough), strip or lane (single-pass parallel), zone or quadrant (indoor standard), wheel or ray (small circular scene).Biological evidence: paper bags only, never plastic. Air-dry wet stains first. Always take a substrate control sample.Blood tubes: EDTA (purple) for DNA and grouping; NaF + K-oxalate (grey) for alcohol estimation.Viscera preservative: saturated NaCl in wide-mouthed glass jars; NaF for blood; never rectified spirit in suspected insecticide poisoning.Arson debris: clean metal paint cans or nylon evidence bags for headspace GC-MS, never plastic zip bags.Firearms: unloaded, packed in rigid box with cable ties through trigger guard; live and fired cartridges packed separately.BNSS 2023 Section 176(3): mandatory FSL visit for offences of seven years or more imprisonment. Section 105: audio-video recording of search and seizure. Section 348: court can compel specimens.BSA 2023 Section 22 relevance, Section 39 expert opinion, Sections 56 to 63 electronic records, Section 63 mandatory electronic-evidence certificate (per Anvar P.V. 2014 and Arjun Panditrao Khotkar 2020).

What is Locard's exchange principle and why is it the foundation of physical evidence?

Edmond Locard formulated the principle around 1910 at the Lyon police laboratory: when two objects come into contact, there is a mutual transfer of material between them. Every contact leaves a trace. The principle is the scientific basis of all trace-evidence work because it predicts that a suspect entering a scene leaves something (fibres, hair, skin cells, soil, gunshot residue) and carries something away. The investigator's job is to find both directions of transfer, and the laboratory's job is to associate the questioned trace with the known source. This is also why every collection protocol asks for a substrate control sample, so the analyst can distinguish transferred material from material native to the substrate.

What is the difference between individual and class characteristics in physical evidence?

Individual characteristics allow association with a single source to the practical exclusion of all others. Examples are fingerprint ridge minutiae, the DNA STR profile across 13 to 20 loci, striations on a fired bullet from a specific barrel, and handwriting from a specific writer. Class characteristics allow only categorisation into a group. Examples are ABO blood group, shoe brand and size, fibre polymer, glass refractive index, and fired-cartridge calibre. Class evidence narrows the suspect pool; individual evidence identifies the source. In court the weight of an opinion turns on which category the underlying feature falls into.

Why are biological samples packed in paper and never in plastic?

Plastic is non-breathable. Any residual moisture in the sample is trapped, encouraging bacterial and fungal growth that destroys DNA within hours and degrades serological markers. Paper bags and breathable cotton cloth allow the sample to continue drying after collection, preserving nuclear and mitochondrial DNA for the long despatch to the CFSL or CDFD Hyderabad. Wet stains are first air-dried at room temperature away from direct sunlight, then packed in paper. The substrate control sample is packed the same way.

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