Crime Scene Investigation Tools, Kits and the Mobile Laboratory | ForensicSpot
Module 2 · Physical Evidences & Detection Devices
Crime Scene Investigation Tools, Kits and the Mobile Laboratory
Basic field kit, investigator's kit, sealed packet bag, and the mobile CSI vans now mandated by BNSS 2023 Section 176(3) for serious offences in Indian states.
A crime scene investigation kit is the physical toolset a Scene of Crime Officer (SOCO) carries to a scene to identify, collect, package and forward physical evidence. In Indian practice, the kit hierarchy runs through four tiers: a basic field kit (carried in every patrol vehicle), an investigator's kit (held by the IO and SOCO), a mobile crime scene laboratory (a vehicle-mounted lab operated by the state FSL), and the main FSL itself. The 2023 push that changed everything is Section 176(3) of the Bharatiya Nagarik Suraksha Sanhita (BNSS), which makes a forensic team visit mandatory at the scene of every offence punishable with seven years or more imprisonment. State FSLs scrambled, and mobile CSI vans went from a Delhi-and-Maharashtra novelty to a national rollout target across Karnataka, Gujarat, Tamil Nadu and a dozen other states.
Here's the bit that the syllabus glosses over. You'd assume the most important item in a CSI kit is something glamorous like the ALS torch or the fingerprint powder. It isn't. The most important item is the sealed packet bag and the wax-thread roll that closes it, because every other piece of evidence has to land inside one. A scene processed with a brilliant ALS sweep but a torn packet bag is a scene that loses at trial. The kit is graded by its weakest link, not its flashiest tool.
Key terms
Basic field kit
The minimum toolset carried in patrol vehicles. Gloves, masks, a torch, sealed packet bags, a swab pack, a measuring tape and a digital camera. Enough to hold a scene until the SOCO arrives.
Investigator's kit
The fuller toolset carried by the IO and SOCO. Adds presumptive test reagents, fingerprint powders and lifters, casting kits, ALS, biohazard containers, evidence labels and the Form 95 forwarding memo book.
Mobile crime scene laboratory
A vehicle-mounted lab operated by the state FSL, equipped to run presumptive tests, develop latent prints, photograph and video-document a scene, and seal forwardable packets on the spot.
Sealed packet bag
A tamper-evident outer envelope that holds the primary container, the case label and the wax-thread or security-tape seal impression. The unit of forwarding from scene to FSL.
BNSS Section 176(3)
The 2023 statutory mandate that a forensic team must visit, collect evidence and videograph at every scene of an offence punishable with seven years or more imprisonment. The legal basis for the state mobile-CSI rollout.
Replenishment SOP
The post-scene process for re-stocking consumables (swabs, gloves, packet bags, reagents) and re-certifying re-usable instruments (camera, ALS, scale) before the kit returns to operational readiness.
01
The four-tier kit hierarchy
From patrol-car toolbox to the main FSL bench.
Indian forensic practice runs the kit chain through four tiers, and the tier that responds depends on the seriousness of the offence and how quickly the scene needs handling. The hierarchy is not academic. It maps directly to who's authorised to do what at the scene, what evidence stays at the scene for the next tier, and what gets shipped onward.
02
What's actually in the basic field kit
The patrol-car toolbox. Small, cheap, always present.
The basic field kit is what every police patrol vehicle in India is supposed to carry, although the supposed and the actual aren't always aligned. The kit's job is simple: hold the scene without contaminating it until the IO and SOCO arrive. The first officer who steps into a scene with a bare hand and a wet shoe has already cost the case more than any reagent will recover.
Contents the syllabus expects you to know cold:
Personal protective equipment. Nitrile gloves (multiple pairs, multiple sizes), surgical masks, shoe covers, hair caps. Indian state SOPs require fresh gloves between every item handled.
Torch and a high-power LED hand-lamp. Most scenes are processed under poor lighting; a 1000-lumen LED is now standard.
Sealed packet bags in three sizes (small for swabs, medium for clothing, large for bulkier items) plus a roll of wax thread and a sealing wax stick. Security tape is the modern alternative.
Cotton swabs and sterile distilled water vials for wet-and-dry biological swabbing.
A measuring tape (5 m and 50 m). The 50 m tape is for outdoor scenes; the 5 m for indoor and item-to-landmark dimensions.
A pocket-size camera or a smartphone in a forensic case-management app. Most state forces now issue 5G-enabled tablets running CCTNS modules.
A notebook and pen (in working ink, in 2026 still important because pencils smudge and digital devices fail).
That's the kit. Nothing in it costs more than a few thousand rupees in total, and the entire kit fits in a single field bag. The discipline is in carrying it, restocking it, and using it.
03
What's actually in the investigator's kit
The fuller toolset. ALS, reagents, fingerprint work and the casting bench.
The investigator's kit is the SOCO-level kit. It adds the tools needed to recognise less-obvious evidence (latent prints, biological stains under ALS, trace fibres), to conduct presumptive tests on the spot, and to lift impression evidence that won't survive transit. Most district-headquarters SOCO units carry a standardised kit issued by the state FSL.
Category
Contents
Primary use
Biological collection
Sterile swabs, distilled water vials, paper envelopes, druggist folds, refrigerated transport box
Blood, semen, saliva, touch DNA
Fingerprint
Black, white and magnetic powders, fibreglass brush, magnetic wand, lifting tape, gelatin lifters, backing cards
Dental stone or Plaster of Paris, mixing bowl, fixative spray, ESDA-grade lifters, casting frames
Footwear, tyre and tool-mark casts
Presumptive test reagents
Kastle-Meyer (phenolphthalein) for blood, leucomalachite green, AP (acid phosphatase) strips for semen, Marquis and Scott for drugs
04
The sealed packet bag, in detail
The unit of forwarding from scene to lab.
The sealed packet bag is the outer envelope that turns a collected item into a forwardable exhibit. The packet bag is the thing the FSL receives, logs at intake, and opens under controlled conditions. If the packet fails at intake (torn, unsealed, mis-labelled, missing memo), the exhibit is sometimes refused outright and almost always weakened at trial.
What a correctly prepared sealed packet looks like:
Outer envelope. Heavy paper or a sturdy plastic-laminated paper. Plastic-only packets are forbidden for biological exhibits because they breed bacteria and degrade DNA.
Case-identifying label. FIR number, IO's name and signature, case-diary serial number for the item, brief description, date and time of collection, location coordinates (GPS or address), and a tested-for field listing what analysis the IO is requesting.
Seal impression. Either a wax-thread closure with the unit's brass seal pressed into a wax pool covering the thread, or a numbered security tape that records the seal serial number on the case-diary entry. The wax-thread method is still standard at most state FSLs because it's the version Indian appellate courts have most clearly affirmed.
Form 95 forwarding memo (the name varies by state) accompanying the packet. The memo lists every packet forwarded under one FIR, with the IO's signature, the seal impression replicated on the memo, and the addressed FSL section.
Tested-for line. Critical and routinely missed. The FSL section's analysis is bounded by what the IO requested. A blood-stained shirt forwarded for "blood grouping" will not get a DNA profile unless DNA is on the tested-for line.
Most courtroom failures of the sealed packet trace back to the same three causes. Either the seal was broken in transit and not re-sealed under a clear chain entry, the memo was missing the IO's signature, or the tested-for line was wrong and the FSL ran the wrong test. None of these are exotic failures; all of them are the kit's discipline failing at the boundary between the scene and the lab. Chain of Custody covers what happens in court when one of these slips.
05
Mobile crime scene vans: what they carry and where they run
A lab on wheels, mandated by BNSS for serious offences.
A mobile crime scene laboratory (often just "the CSI van") is a vehicle-mounted lab operated by the state FSL. Indian deployments are typically built on a 4x4 SUV chassis or a small truck, with a generator, a powered work surface, a refrigerated specimen compartment, a photography and videography rig, a presumptive testing bench, and a latent-print development station. The van turns a scene visit from a recognise-collect-forward exercise into a recognise-test-confirm-forward exercise, which is faster and more defensible.
The BNSS push made these vans non-optional. Section 176(3) of the Bharatiya Nagarik Suraksha Sanhita 2023 mandates that a forensic team visit the scene, collect physical evidence and videograph the proceedings for every offence punishable with seven years or more imprisonment. The earlier CrPC framework treated the FSL visit as discretionary; BNSS made it the rule. State governments responded by procuring CSI vans at scale.
Where the vans actually run, by mid-2026:
Delhi. The FSL Rohini operates around 14 mobile CSI units across the seven district commissionerates. Deployed primarily for homicide, sexual offence and major arson scenes.
Maharashtra. The Directorate of Forensic Science Laboratories runs a fleet of roughly 50 mobile units across the state, with each district FSL having at least one assigned vehicle. Mumbai's fleet is the largest.
Karnataka. Roughly 35 mobile units operate out of Bengaluru, Mysore, Mangaluru, Hubballi and the smaller divisional centres. Bengaluru's Madiwala FSL anchors the urban response.
Gujarat. A state-wide rollout under the Directorate of Forensic Sciences, with around 30 vehicles distributed across districts, the largest concentration in Ahmedabad and Surat.
Tamil Nadu. Around 40 units across the state, anchored at the FSL Chennai with district reach into Madurai, Coimbatore, Tiruchirappalli and Salem.
Smaller fleets are now operational in Uttar Pradesh (around 25 units), Telangana, Andhra Pradesh, Haryana, Punjab and Kerala. NFSU's training centre in Gandhinagar runs the standardised mobile-unit curriculum for state FSL personnel.
What a typical CSI van actually carries (the contents map closely to the investigator's kit, but with scene-side analytical capability added):
Onboard generator (3-5 kVA), inverter, multiple 230 V outlets, climate control (specimens degrade in 40°C+ summer interiors).
06
Replenishment SOPs and chain-of-custody implications
The bit that decides whether the next scene gets a working kit.
Replenishment is the unglamorous post-scene work that decides whether the kit is fit for the next deployment. Most state SOPs follow a consistent pattern, and the FACT syllabus tests it because the gap between policy and practice is wide.
On-scene closure
Before leaving the scene, the SOCO inventories what was consumed: number of gloves and masks, swabs used, packet bags sealed, reagent vials opened, casting kits expended. The inventory goes into the case diary and the kit's running consumption log.
Return to base
The kit returns to the district or state FSL store-room within the operational window (typically 24 hours). Any sealed packets travel separately with the IO under the chain-of-custody protocol; the kit itself returns with the SOCO.
Store-keeper handover
The kit is signed back in with the FSL's store-keeper, who tallies the consumption log against the returned items. A discrepancy (gloves logged as used but the box still feels heavy, vials missing from the rack) is flagged and investigated. This step is where most state SOPs are weak in practice.
Practice
Question 1 of 5· 0 answered
Under BNSS 2023 Section 176(3), a forensic team's visit to a scene is mandatory when the offence is punishable with:
Frequently asked questions
What is the difference between a basic field kit and an investigator's kit?+
The basic field kit is the minimum toolset carried in every patrol vehicle: PPE, sealed packet bags, swabs, torch, measuring tape and a camera. Its job is to hold the scene until the SOCO arrives. The investigator's kit is the SOCO-level toolset that adds ALS, presumptive reagents, fingerprint powders, casting kits and biohazard containers. It does the recognition, presumptive testing and collection work.
What does BNSS Section 176(3) require for forensic teams at a crime scene?+
Section 176(3) of the Bharatiya Nagarik Suraksha Sanhita 2023 mandates that a forensic expert visit the scene, collect evidence and videograph the proceedings for every offence punishable with seven years or more imprisonment. This replaced the earlier CrPC framework where the FSL visit was discretionary and triggered the national rollout of state mobile CSI vans.
What is inside a mobile crime scene investigation van?+
A typical Indian CSI van carries a generator and power supply, a refrigerated specimen compartment, a presumptive testing bench with the standard reagent set, a latent print development station, photography and videography kits, GPS and a CCTNS terminal, biohazard handling supplies, and sealed packet bag stock with wax-thread sealing materials. The van turns a scene visit into a triage-test-seal exercise rather than just a collect-and-forward exercise.
Which Indian states currently operate mobile CSI vans?+
As of 2026, mobile CSI van fleets are operational in Delhi (FSL Rohini, around 14 units), Maharashtra (around 50 units), Karnataka (around 35 units), Gujarat (around 30 units), Tamil Nadu (around 40 units), Uttar Pradesh (around 25 units), Telangana, Andhra Pradesh, Haryana, Punjab and Kerala. NFSU Gandhinagar runs the standardised training curriculum.
The four-tier kit hierarchy. The basic field kit holds the scene; the investigator's kit does the recognition and collection work; the mobile CSI van runs scene-side presumptive tests and produces sealed packets; the main FSL does the confirmatory analysis. Capability grows at each tier, response time grows with it, and the BNSS 2023 mandate now pushes tier 3 to every serious-offence scene.
The capability grows at each tier, but the discipline at every tier is the same: nothing leaves a tier in a state worse than it arrived. Tier 1 holds the scene without contaminating it. Tier 2 recognises and lifts without destroying. Tier 3 produces a sealed packet that survives transit. Tier 4 opens the packet, runs the confirmatory test, and signs the report. The chain of custody you read about in Chain of Custody is what stitches the tiers together.
Scene-side preliminary identification
Optical aids
ALS unit (multiple wavelengths), UV torch, magnifier, orange and yellow viewing goggles
Wax thread roll, sealing wax sticks, brass seal of the unit, security tape with serial numbers
Tamper-evident closure of every packet
A few field pragmatics that aren't in the textbooks:
The ALS unit is the single most expensive item in the kit (typically ₹40,000 to ₹2,00,000 for a multi-wavelength unit), and it's the item most often left behind because of weight. Don't.
Presumptive reagents have shelf lives. Most state SOPs require a fresh batch every six months, with the date stamped on each vial. An expired Kastle-Meyer can produce a false negative that misses a wiped-down blood scene.
Magnetic powder is gentler on porous surfaces (untreated wood, leather) than standard powders. Most candidates miss this because the FACT syllabus lists powders as one item.
The casting frame for plaster work is often improvised from a plastic strip; the kit's frame is for the situations where time matters and improvisation costs evidence.
Power and environmental.
Refrigeration. A small forensic-grade refrigerator for biological samples, holding 2-8°C, and a freezer compartment for samples that need lower temperatures pending FSL transit.
Presumptive testing bench. Folding work surface with reagent racks, calibrated pipettes, disposable plastic pipettes, and the standard reagent set (Kastle-Meyer, leucomalachite, AP, Marquis, Scott, Duquenois-Levine).
Latent print station. Powder bench, magnetic wand, cyanoacrylate fuming chamber for porous surfaces (some vans, not all), and a dedicated photo bench for development photography.
Photography and videography. Tripod, full-frame DSLR with macro and wide lenses, video camera with date-time overlay, drone for outdoor overheads (newer vans). The videography kit is the BNSS 176(3) requirement.
GPS and case-management terminal. A laptop or tablet running the state CCTNS module, with offline capability and sync-on-return.
Sealed packet bag stock. Multiple sizes, wax-thread rolls, sealing wax, the unit's brass seal, security tape rolls, and a stock of Form 95 forwarding memo books.
Biohazard handling. Sharps boxes, double-bagged pouches, full PPE for two operators, decontamination wipes for the van's interior between scenes.
Restocking
Consumables are replaced from the central store: fresh gloves, masks, swabs, packet bags, wax-thread rolls, sealing wax, reagent vials with the new expiry date, casting media, Form 95 memo books. The replacement is logged with batch numbers for traceability.
Instrument re-certification
Re-usable instruments are checked. The camera's flash, focus and date stamp are tested with a calibration frame. The ALS unit's wavelength output is verified against a reference card. The GPS unit's positional accuracy is checked against a known landmark. Any instrument outside its tolerance is pulled out of service and re-calibrated by the FSL's instrumentation cell.
Seal stock check
The unit's brass seal is checked for legibility. Wax-thread stock is replenished. Security tape rolls are checked for serial-number sequence continuity (the next serial in stock is recorded so a torn or missing tape during the next scene is detectable).
Operational readiness sign-off
The store-keeper and the SOCO co-sign the kit's readiness log. The kit is now operational for the next deployment. Most state SOPs require this sign-off within 48 hours of return; longer delays disqualify the kit from urgent response.
The chain-of-custody implication is the bit candidates miss. Every replenishment item that touches a sealed packet (wax, thread, security tape) has to come from a logged stock with a batch number traceable to the state FSL's central store. If the defence at trial argues that the wax used to seal the packet came from an unverifiable stock, the court is asked to doubt the seal. State SOPs answer this by maintaining batch numbers in the replenishment log and recording the batch in use on the case diary for each scene. It's a paper trail, but it's the paper trail that holds the seal at trial.
A few replenishment failures the syllabus expects you to recognise:
The expired reagent. A presumptive vial past its shelf life produces unreliable results. The fix is the six-month rotation discipline.
The torn packet bag. An unflagged tear in stock means a packet sealed at the scene was already compromised on issue. The fix is the store-keeper's intake check.
The depleted wax-thread roll. A roll close to the end produces a thin seal that won't hold. The fix is the consumption log triggering a restock at 25% remaining.
The uncalibrated camera flash. A flash that has drifted in output produces under-exposed close-ups. The fix is the calibration-frame check on every return.
What is a sealed packet bag and why does it matter at trial?+
A sealed packet bag is the tamper-evident outer envelope that holds the primary container, the case-identifying label and the seal impression (wax-thread or security tape). It's the unit of forwarding from the scene to the FSL. At trial, the packet's integrity is what the defence challenges first: a torn envelope, a missing IO signature, an unverifiable seal stock or a wrong tested-for line can each unravel the chain of custody.
How are CSI kits replenished after a scene, and why does it affect chain of custody?+
Replenishment follows a defined SOP: on-scene consumption inventory, return to base within 24 hours, store-keeper handover with discrepancy check, restocking from the central store with batch numbers logged, instrument re-certification (camera, ALS, GPS), seal stock verification, and operational readiness sign-off within 48 hours. The chain-of-custody implication is that every wax stick, thread roll and security tape used to seal a packet must trace back to a logged batch number, otherwise the defence can ask the court to doubt the seal at trial.
Why is the presumptive test in a mobile lab not court-admissible on its own?+
Presumptive reagents like Kastle-Meyer for blood or Marquis for drugs produce a strong colour change in the presence of the target substance, but false positives are possible with other compounds (plant peroxidases for Kastle-Meyer, certain over-the-counter medications for Marquis). The presumptive is a triage tool that justifies the cost of confirmatory analysis. Indian courts treat presumptive results as preliminary and require confirmatory FSL testing (DNA, GC-MS, immunoassay) for primary evidentiary use.