Evidence. Collection Explosion usually followed by fire Often destroyed by one or other Dangerous – shards of glass or metal, toxic or flammable vapors,

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Presentation transcript:

Evidence

Collection Explosion usually followed by fire Often destroyed by one or other Dangerous – shards of glass or metal, toxic or flammable vapors, 2 nd explosion Large crater = point of origin

Collect soil and debris from inside crater Test nearby objects for explosive residue or pieces of detonator Use sieves to sift for small pieces Follow chain of custody Package separately in metal containers – label where found

Analysis ID types of explosives & mechanisms of detonation First – preliminary tests, then confirmatory tests

Use stereomicroscopy - examine debris for unexploded material - look for certain shapes and colors - look for pieces of wrapper from dynamite, metal from pipe, pieces of wire

Chemical Analysis Wash debris w/ acetone to dissolve explosives Color Spot Test – screens for various explosives Mix small amount of conc. acetone & explosive solution with a specific reagent – observe

Several tests – - Modified Griess Test – presence of nitrite (NO 2 -) (orange) - Alcoholic Potassium Hydroxide (KOH) – presence of TNT (blue or violet) - Diephenylamine – most explosive residues (not TNT or RDX) (blue or black)

Reactions ExplosiveModified Griess Test Alcoholic KOHDiphenylamine NitrateNone Blue to Blue-Black Nitrocellulose Nitroglycerine Trinitrotoluene (TNT) RDX PETN

Reactions ExplosiveModified Griess Test Alcoholic KOHDiphenylamine NitrateNone Blue to Blue-Black NitrocelluloseOrangeNoneBlue-Black Nitroglycerine Trinitrotoluene (TNT) RDX PETN

Reactions ExplosiveModified Griess Test Alcoholic KOHDiphenylamine NitrateNone Blue to Blue-Black NitrocelluloseOrangeNoneBlue-Black NitroglycerineOrangeNoneBlue to Blue-Black Trinitrotoluene (TNT) RDX PETN

Reactions ExplosiveModified Griess Test Alcoholic KOHDiphenylamine NitrateNone Blue to Blue-Black NitrocelluloseOrangeNoneBlue-Black NitroglycerineOrangeNoneBlue to Blue-Black Trinitrotoluene (TNT)NoneRed to VioletNone RDX PETN

Reactions ExplosiveModified Griess Test Alcoholic KOHDiphenylamine NitrateNone Blue to Blue-Black NitrocelluloseOrangeNoneBlue-Black NitroglycerineOrangeNoneBlue to Blue-Black Trinitrotoluene (TNT)NoneRed to VioletNone RDXOrangeNone PETN

Reactions ExplosiveModified Griess Test Alcoholic KOHDiphenylamine NitrateNone Blue to Blue-Black NitrocelluloseOrangeNoneBlue-Black NitroglycerineOrangeNoneBlue to Blue-Black Trinitrotoluene (TNT)NoneRed to VioletNone RDXOrangeNone PETNOrangeNoneBlue

Chromatography TLC – Thin Layer Chromatography Calculate R f values Compared to knowns Can also use HPLC

Confirmatory Tests After prelim ID Infrared spectroscopy or Gas chrom – Mass spec – confirm ID of organics (TNT, military explosives)

Physical Evidence Clues about perpetrator Pieces of wire, pipe, detonators – fingerprints, explosive residue on clothes, serial number on watch, tool marks on pipe, torn edges of duct tape