Evidence

Collection

• Explosion usually followed by fire• Often destroyed by one or other• Dangerous – shards of glass or metal, toxic or

flammable vapors, 2nd 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 –

• Several tests – - Modified Griess Test – presence of nitrite

(NO2-) (orange)- Alcoholic Potassium Hydroxide (KOH) –

presence of TNT (blue or violet)- Diephenylamine – most explosive

residues (not TNT or RDX) (blue or black)

Reactions

Explosive Modified Griess Test

Alcoholic KOH Diphenylamine

Nitrate None None Blue to Blue-Black

Nitrocellulose

Nitroglycerine

Trinitrotoluene (TNT)

RDX

PETN

Reactions

Explosive Modified Griess Test

Alcoholic KOH Diphenylamine

Nitrate None None Blue to Blue-Black

Nitrocellulose Orange None Blue-Black

Nitroglycerine

Trinitrotoluene (TNT)

RDX

PETN

Reactions

Explosive Modified Griess Test

Alcoholic KOH Diphenylamine

Nitrate None None Blue to Blue-Black

Nitrocellulose Orange None Blue-Black

Nitroglycerine Orange None Blue to Blue-Black

Trinitrotoluene (TNT)

RDX

PETN

Reactions

Explosive Modified Griess Test

Alcoholic KOH Diphenylamine

Nitrate None None Blue to Blue-Black

Nitrocellulose Orange None Blue-Black

Nitroglycerine Orange None Blue to Blue-Black

Trinitrotoluene (TNT) None Red to Violet None

RDX

PETN

Reactions

Explosive Modified Griess Test

Alcoholic KOH Diphenylamine

Nitrate None None Blue to Blue-Black

Nitrocellulose Orange None Blue-Black

Nitroglycerine Orange None Blue to Blue-Black

Trinitrotoluene (TNT) None Red to Violet None

RDX Orange None None

PETN

Reactions

Explosive Modified Griess Test

Alcoholic KOH Diphenylamine

Nitrate None None Blue to Blue-Black

Nitrocellulose Orange None Blue-Black

Nitroglycerine Orange None Blue to Blue-Black

Trinitrotoluene (TNT) None Red to Violet None

RDX Orange None None

PETN Orange None Blue

Chromatography

• TLC – Thin Layer Chromatography• Calculate Rf values• Use cellulose or silica gel plates as stationary

phase• Mixture of unknown explosives rinsed w/

solvent• 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)

• IR spec – IR light passes thru sample and measures amount of energy it absorbs

• GC-MS – GC separates compounds in mixtureMS – compounds broken into smaller

charged particles – separated by mass & charge

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