Country-Made Bombs and Improvised Explosive Devices (IEDs)

The four-component model is the core analytical framework for any IED analysis.

1. Initiator. Delivers shock or heat to fire the main charge. Options: commercial electric blasting cap, non-electric cap fired by safety fuse or shock tube, sutli (nitrate-soaked twine) fuse for desi bombs. Indian commercial detonators carry batch and serial markings under the Explosives Rules 2008.
2. Main charge. The bulk explosive. Desi bombs use low explosive (potassium chlorate plus sulphur, or KNO3 plus S plus charcoal black powder). Pressure-cooker, tiffin and vehicle-borne devices favour high explosive (RDX, TNT, PETN, or ammonium-nitrate ANFO). The chemistry side is covered in explosives definition, types and classification.
3. Switch (trigger). Closes the firing circuit. Four families: time-delay (digital watch, analog clock, capacitor RC delay), command-wired, radio-controlled (cell phone, RC car remote), victim-operated (pressure plate, tripwire, anti-handling).
4. Power source. Battery (9 V, AA, button cell), capacitor, or mechanical spring. The same battery brand across multiple scenes is a classic bomb-maker signature.
5. Container or casing. Confines the blast (raises peak over-pressure) and supplies shrapnel. Pipe, pressure cooker, tiffin box, suitcase, vehicle chassis, body-worn vest.

The firing chain runs in a fixed order: power source closes through the switch into the initiator, which fires the main charge, confined by the container. Every device, regardless of type, follows this sequence.

The country-made bomb is the cheapest improvised device in Indian casework. A low-explosive mixture (potassium chlorate plus sulphur, or KNO3 plus sulphur plus charcoal black powder, or amorphous phosphorus plus KClO3 for the sensitive variants) is packed into a small parcel, wrapped tightly in jute, layered paper or sutli (twine), and fitted with a fuse of sutli soaked in saltpetre, or in upgraded versions a short safety fuse with a nitrocellulose detonator.

The device is hand-thrown. Effective lethal radius is small (under five metres), but the wrap fragments into a low-grade shrapnel pattern that causes penetrating soft-tissue injury at close range. Indian casework anchors include the West Bengal political-violence cycle (Birbhum, Murshidabad, Nadia), Bihar and eastern UP rural conflicts during election periods, and routine seizures of cottage-industry bomb factories during pre-poll combing operations. Trial under the Explosive Substances Act 1908.

Four-component map: power source absent (fuse lit manually), switch absent (fuse acts as time delay), initiator is the sutli or nitrocellulose fuse, main charge is the low-explosive mixture, container is the jute and paper wrap.

Beyond the desi bomb, the next four families are defined by their containers. Each has a typical charge and a documented Indian incident that illustrates the forensic pattern.

Pipe bombs. Steel or PVC pipe sealed at both ends with threaded end caps, packed with low or high explosive, fitted with a fuse or electrical initiator. The end caps fragment on detonation and form the primary shrapnel. Common in Indian Maoist (CPI-Maoist) insurgency casework in the Bastar belt and in early IRA campaigns. Recovered end-cap fragments often retain partial thread patterns that match a specific hardware lot.

Pressure-cooker bombs (the Indian signature pattern). A steel pressure cooker packed with high explosive (RDX, or an RDX plus ammonium-nitrate slurry), with added shrapnel (nuts, bolts, ball bearings, nails) layered around the charge. The cooker body confines the blast to a much higher peak over-pressure than an open charge of the same mass, which is why the device is disproportionately lethal in crowded indoor spaces. Trigger is a timer (digital watch wired to a battery and relay) or a radio link. Casework anchors:

• 2006 Mumbai train blasts (11 July 2006). Seven pressure-cooker bombs on Western Railway local trains during the evening rush. RDX plus ammonium nitrate. Timer-detonated.
• 2008 Mumbai 26/11 attacks. Multiple pressure-cooker bombs deployed alongside the small-arms assault, with devices recovered or detonated at CST station, the Cama Hospital area, and an abandoned taxi.
• 2013 Boston Marathon bombing. Two pressure-cooker bombs near the finish line. International parallel cited in NSG training materials.

Tiffin bombs. Stainless-steel lunch boxes packed with explosive and fitted with an electrical initiator and timer. The defining Indian case is the 1993 Mumbai serial blasts ("Black Friday")of 12 March 1993: a coordinated wave of RDX-loaded vehicles and tiffin bombs hit the Bombay Stock Exchange, Air India Building, hotels and bazaars, killing over 250 people. The Mumbai 1993 investigation under TADA shaped the modern Indian post-blast exploitation playbook.

Nail bombs and shrapnel-enhanced devices. Any of the above with deliberately added fragmentation (nails, ball bearings, washers, broken glass) packed around the main charge. The shrapnel injury pattern, which parallels the entry-wound framework in firearm injuries: entry, exit and rangeis what tells the post-mortem pathologist the device was shrapnel-enhanced rather than pure blast.

The container can scale up (vehicle) or scale down (parcel) without changing the four-component logic.

VBIED (Vehicle-Borne IED). A car, SUV, truck or two-wheeler loaded with bulk explosive, driven to the target and detonated. The defining recent Indian case is the Pulwama attack of 14 February 2019 a Maruti Eeco carrying roughly 200 kilograms of explosives (RDX combined with ammonium nitrate, gelatin sticks, and aluminium powder) was rammed into a CRPF convoy on the Jammu-Srinagar highway, killing 40 personnel. Post-blast NIA investigation under UAPA recovered chassis fragments, residue swabs and detonator components.

SBBIED (Suicide Bomber-Borne IED). A belt or vest worn by the bomber, packed with high explosive (commonly RDX in Indian casework) and ball-bearing shrapnel, fired by a hand-held switch. The Rajiv Gandhi assassination at Sriperumbudur on 21 May 1991 by an LTTE operative wearing a belt-worn RDX device is the case Indian textbooks open with. The recovered switch button and belt buckle became the forensic exploitation template Indian agencies still use.

Letter and parcel bombs. Small charge inside an envelope or parcel, often fired by an anti-handling switch released when the flap is opened. Historically used during the Punjab insurgency of the 1980s and 1990s. Rare in current Indian casework but documented in historical investigations.

The forensic examination of an IED runs across three phases and three agencies.

Phase 1: Render-safe. A suspect device is approached by the NSG Bomb Data Centre (for high-value or terrorism-classified scenes) or by the state Bomb Disposal Squad (for routine criminal scenes). The team cordons to standoff distance, then images the device in place using a portable X-ray (transmission imagers such as 3DX-RAY or Golden Engineering units) to map the four components without opening the casing. Render-safe is then executed using a disruptor (water-cannon or PAN disruptor that interrupts the firing circuit), or by a robot (indigenous DRDO Daksh, or imported Andros / iRobot Packbot platforms) carrying the disruptor to the device. Manual approach in a bomb suit is the last resort.

Phase 2: Recovery (post-blast scene exploitation). If the device has already detonated, the scene is gridded into quadrants centred on the crater. Every fragment within a defined search radius is recovered, bagged, labelled and logged. Priority targets: timer chip or watch fragments, battery casing, switch parts, electronic-board fragments, and the initiator (detonator) casing. Intact detonator casings often carry the manufacturer batch marking required by the Explosives Rules 2008. Residue swabs from the crater walls and near-field objects feed the forensic analysis of explosives and post-blast residuescovered in the next bullet.

Phase 3: Exploitation and chargesheet. Recovered fragments and swabs go to the CFSL Hyderabad post-blast laboratory and, for central counterterrorism casework, to the NSG forensic exploitation cell. Fragment analysis (crater dimensions, fragment dispersion, recovered switch and circuit-board components) tells the lab what device type was used and gives a "bomb-maker signature": tape brand and colour, wire colour scheme, switch model, IC number on the circuit board, soldering style. The NIA then files the chargesheet under the Unlawful Activities (Prevention) Act and the Explosive Substances Act 1908, with the forensic report admitted under Section 39 of the Bharatiya Sakshya Adhiniyam 2023 (see BSA forensic evidence in court). Every transfer is logged in the chain-of-custodyregister, with sealed-container labelling and tamper-evident packaging.

Scene management (seat-of-explosion identification, debris layering, crater analysis) is covered separately in the investigation of explosion and arson casesbullet.

Defence counsel attacks IED forensic reports on three predictable lines.

Chain of custody on recovered fragments. Post-blast scenes carry hundreds of fragments across multiple agencies (state police, BDS, NSG, NIA, CFSL). A missing entry on a critical fragment (the timer chip, the detonator casing) can sink its admissibility. The CFSL Hyderabad SOP uses sealed evidence cans, tamper-evident packaging, and dual signatures at every transfer.

Residue cross-contamination. Trace RDX, PETN or nitrate residues are detectable at nanogram levels by IMS (Smiths IONSCAN) and LC-MS. That sensitivity is also the vulnerability: a clothing or vehicle swab could pick up contamination from a previous scene or the swabber's own residue history. The SOP defence is the field blank, run alongside every active sample.

The bomb-maker signature claim. Linking two scenes to one bomb-maker on the basis of wire colour, tape brand and circuit-board topology is reasonable, but the defence will argue these are class characteristics. The honest report says "consistent with" rather than "uniquely matches", and the chargesheet builds the signature claim on a cluster of indicators.