Evidence Collection Handbook - EXPLOSIVES

An explosive is a substance which, through chemical reaction, violently changes into a gas, creating much pressure and liberating much heat. Explosives are divided into two classes: low-order and high-order explosives.

With low-order explosives, the rate of change to gaseous state is relatively slow and must be in a compressed or enclosed state to explode. Low-order explosives tend to produce large chunks of debris. Examples of low-order explosives are black powder, smokeless powders, volatile flammable liquids, and flammable gases. These explosives can also be called deflagration agents. A dust or grain explosion can also be considered a low-order explosion.

In high-order explosives, the rate of change to the gaseous state is extremely rapid. They tend to pulverize everything nearby. Compression or enclosing the explosive is not required. Such an explosion is said to detonate. High-order explosives include dynamite, military explosives, TNT, PETN, Composition C, and mixtures of ammonium nitrate and fuel oil.

Information Determined.

1. Debris and soil close to the point of detonation are likely to bear residue from the explosive. From this residue, the type of explosive used frequently can be determined.
2. An examination of blasting caps, wires, batteries, fuses, containers and boxes, etc. sometimes makes it possible to identify the manufacturer.

Collection of Evidence.

Handling Bombs.

1. DON'T, UNLESS YOU'RE QUALIFIED! Obtain the services of explosive experts. You should have available the names of the nearest qualified disposal experts in the event one must be handled.
2. Don't move or touch anything connected with it.
3. Clear the area and post guards outside the danger area.
4. Shut off fuel, electricity, and gas and remove flammable material.
5. Notify fire and rescue squads.
6. Obtain a portable X-Ray machine if the expert requests it and obtain mattresses and sandbags for use as baffles and shields if necessary.

Collecting Evidence at the Scene of an Explosion and On-Site Determination.

1. The effects of the two classes of explosives are different. Low-order explosions tend to "push" rather than shatter. Large chunks of debris result. Twisting and tearing of objects tend to occur. High-order explosives tend to shatter and fragment material near the center of detonation, and there is much evidence of impact by small, high-velocity missiles near the center of detonation. The resulting debris is in small fragments.
2. Evidence of accessories used in the explosions may be found. Some examples are fragments of blasting caps, safety fuse fragments, wire, matches, match folders, fuse lighters, batteries or other sources of electric current, fragments of a timing device, delay mechanisms, or switches. Information of these accessories assist in the investigation. Containers or material foreign to the scene should be collected.
3. Unusual odors should be noted.
4. The site should be checked for fingerprints, footprints, tire tracks and tool marks.
5. The laboratory does not accept large quantities of explosives. It does not have the facilities for storage of such material. Requests for the identification of residues of explosives from debris is the usual request; however, if an intact explosive is needed to be identified, only a small amount is needed. Just a few grams, or about the amount in level teaspoon, is needed for analysis.

Disposition of Dynamite and Black Powder.

Disposition is best handled by someone familiar with explosives.

Shipment.

For explosive devices, follow the instructions of the explosives expert for disposal and evidence collection. For blast scenes, package debris in plastic bags or arson cans if possible. Call the lab for advice on exploded material, blasting caps, and other detonating material. Analysis of explosives is currently limited to the Central Forensic Laboratory in Frankfort.

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