Post-Blast Residue (PBR)
Definition
Unconsumed explosive plus reaction by-products left at the seat of an explosion, on debris, on fragments and on the hands or clothing of anyone who handled the device. The forensic analyte of every blast case.
- Composition
- Unconsumed explosive plus reaction by-products
- Recovery sites
- Seat of explosion, debris, fragments, hands and clothing
- Typical analysis
- Ion mobility spectrometry, GC-MS and swab colour tests
- Role
- Primary analyte in blast-scene investigation
Common questions
Why does hand or clothing residue matter for suspect linkage?+
Trace PBR transferred onto a handler's skin or clothing during device assembly or detonation can place a suspect in contact with the explosive material, independent of scene evidence, though it degrades and can also transfer innocently, so it is corroborating rather than conclusive on its own.
Why is PBR often present only in trace quantities?+
Most of the explosive charge converts to gas during detonation, leaving only a small unreacted fraction plus by-products, and what remains is further reduced by fire, water used to fight it, and weathering before collection.
Related terms
- Diphenylamine Test
- Color test for nitrates and nitro groups. Diphenylamine in conc. H2SO4 turns deep blue with oxidising NO3-/NO2-. Also a primer-residue test, which...
- GC-TEA
- Gas chromatography with a Thermal Energy Analyser. Pyrolytic cleavage of the nitro group to NO followed by chemiluminescent reaction with ozone. Nitro-specific,...
- IMS
- Ion Mobility Spectrometry. Drift-tube separation of gas-phase ions at ambient pressure. Smiths IONSCAN 500DT and Sabre 5000 give 5-second field screening on...
- Ion Chromatography (IC)
- An analytical technique that separates and quantifies anions and cations in solution. In post-blast residue analysis, IC detects nitrate, nitrite, ammonium, and...
- Janowski Test
- Color test for nitroaromatics. Sample plus DMSO plus alcoholic KOH gives a violet Meisenheimer complex. Positive for TNT, picric acid, tetryl and...
- Modified Griess Test
- A contact-transfer colour chemistry test for nitrite-containing propellant combustion residue. Sulphanilic acid undergoes diazotisation with nitrous acid (from NO2 on the target...
- VBIED
- Vehicle-Borne Improvised Explosive Device. Pulwama 2019 is the recent Indian reference case (RDX plus ammonium nitrate).