Ch. 19 Arson and Explosives Investigations

2. What two factors are needed to cause a fire?

A source of heat and material ignited.

ultraviolet fluorescence

A technique in which a darkened fire scene is illuminated with an ultraviolet lamp so that certain substances glow; used to detect residues of accelerants and to locate the point of a fire's origin.

spontaneous heating

An increase in temperature that results from a natural process; caused by chemical action, fermentation, or oxidation

Property Insurance Loss Register (PILR)

An insurance industry database that lists the insureds in burglary and theft claims and everyone with an insurable interest in fire claims; detects repeated patterns of claim activity.

catalytic combustion detector

a portable device that oxidizes any combustible gases in a sample; used to detect residues of flammable-liquid accelerants at fire scenes

19. What is the definition of an improvised explosive device (IED)?

A combination of items/components that are neither designed nor produced to be used in conjunction with each other, but when placed together/assembled, constitute a mechanism that has the capacity of exploding and causing personal injuries/property damage.

incendiary device

A device or mechanism used to start a fire or explosion.

infrared spectrophotometer

A device that identifies samples by recording the amount of infrared light that poses through them; used to detect residues of flammable-liquid accelerants at fire scenes.

flame ionization detector

A device the produces ionized molecules in proportion to the amount of combustible organic gases in a sample; used to detect residues of accelerants at fire scenes.

explosion

A physical reaction characterized by the presence of high pressure gas, confinement of the pressure, rapid release of the pressure, and change or damage to the confining structure, container, or vessel as a result of the pressure release.

gas liquid chromatograph (GLC)

A portable device that separates a sample gas into measurable components; used to detect residues of accelerants at the scene.

burn indicators

Any effects of heat or partial burning that indicate a fire's rate of development, points of origin, temperature, duration, and time of occurrence and the presence of flammable liquids.

pyromaniac

Arsonists who lack conscious motivation for their fire setting.

9. Why should uncoated metal paint cans (or similar containers), not plastic bags or containers, be used for the storage of material suspected of containing flammable liquids?

Because plastic gives off hydrocarbons that contaminate the recovered material.

blast fragmentation

Devices may be constructed with high or low explosives. They use a hard case container such as a metal pipe or other suitable enclosure or have fragmentation shrapnel added to or around the main charge explosive. These types of IEDs use the explosive to propel casualty-producing fragmentation and shrapnel throughout the scene.

5. What types of burn indications can be examined by the arson investigator to assist in determining whether a fire is accidental or incendiary in nature?

Effects of heat, point of origin, duration, temperature, and time of occurrence well as presence of flammable liquids.

4. What are some of the more common causes of accidental or natural fires?

Electrical appliances/equipment, the electric system, gas, heating units, sunlight, matches, and smoking.

mechanical explosion

Explosions in which a high-pressure gas is produced by purely physical reactions; commonly caused by steam (e.g., the bursting of a steam boiler).

chemical explosion

Explosions in which a high-pressure gas is produced by reactions that involve changes in the basic chemical nature of the fuel; commonly caused by burning of the hydrocarbon fuels (e.g., natural gas, gasoline, lubricating oils).

shaped charge

Explosives specifically designed and constructed to achieve a very specific result, namely the blasting of a hole through metal and other types of hardened material.

layer-checking technique

In arson investigation, the process of examining the strata of debris, working through to the floor; may indicate the sequence of burning.

trailer

In arson, any substance used to spread the fire from the plant to other parts of a room or building.

plant

In arson, the material placed around the ignition device to feed the flame.

effective fire temperatures

In structural fires, identifiable temperatures which reflect physical effects that can be defined by specific temperature ranges.

What kind of data is available within the ATF's U.S. Bomb Data Center (USBDC)?

It is the primary source for explosives-related intelligence and information in the United States.

1. If arson is suspected, why should firefighters not alter the premises, such as by mopping up or over-hauling the scene of the fire, especially at the point of origin?

It may destroy valuable physical evidence.

6. What are some of the most commonly used ignition and timing devices in the commission of arsons?

Matches, gasoline/accelerants, chemicals, gas, electrical systems, and mechanical devices.

13. What are the two basic types of explosions? Briefly describe each.

Mechanical and chemical.

8. What are some of the most common motives for arson?

Profit, personal revenge, societal retaliation, institutional retaliation, and group retaliation.

11. What types of individuals might be able to provide information relevant to the fire?

Tenants, businesspeople, taxi drivers, sanitation people, and delivery people.

12. What is the purpose of the National Insurance Crime Bureau?

The National Insurance Crime Bureau (NICB) is a U.S. insurance industry trade association focused on preventing, detecting and defeating insurance fraud and vehicle theft through information analysis, investigations, training, legislative advocacy and public awareness.

spalling

The breakdown in the surface tensile strength of concrete, masonry, or brick that occurs when exposure to high temperatures and rates of heating produces mechanical forces within the material.

spontaneous ignition

The catching afire of material subjected to spontaneous heating; usually requires several hours to several months of oxidation or fermentation.

alligatoring

The checking of charred wood, which gives it the appearance of alligator skin.

20. What are the basic components of an improvised explosive device?

The main charge explosive and the fuzing system.

3. What is the layer-checking technique, and how can it assist in determining the cause and the origin of a fire?

The process of examining the strata of debris, working through to the floor; these layers often contain wood ash, plaster, melted aluminum, window glass, charred drapery fabric, and charred newspapers; may indicate the sequence of burning.

charring

The scorching of materials by fire; used to deduce the direction of fire spread by comparing relative depths of char throughout the scene.

improvised explosive device

This is a combination of items or components that are neither designated nor produced to be used in conjunction with each other, but when placed together or assembled, constitute a mechanism that has the capability of exploding and causing personal injuries and property damage.

bomber's signature

This refers to an identifiable pattern or characteristic of using essentially the same or similar bomb construction components and construction fabrication and design techniques for multiple bombs.

14. What are the principal objectives of an explosion scene investigation?

To determine the origin, identify the fuel/ignition sources, determine the cause, and establish responsibility for the incident.

15. What is the first duty of the investigator at the scene of an explosion?

To secure the scene.

10. What are some of the advantages and disadvantages of olfactory detection in determining the presence of fire accelerants at the scene of a fire?

advantages: the nose is as sensitive as any of the currently available detecting equipment disadvantages: - there are flammable liquids that the nose is not sensitive to - the nose tends to lose its sensitivity to an odor after prolonged or intense exposure to it - the odor of fire accelerants may be masked by another strong odor - somewhat impractical or impossible to search with the nose for accelerant odors along floors or recessed areas

21. What does the term "bomber's signature" mean?

an identifiable pattern or characteristic using essentially the same or similar bomb construction components and construction, fabrication, and design techniques for multiple bombs

18. Once the origin, or epicenter, of the explosion has been identified, the investigator should determine what type of fuel has been employed. How is this typically done?

by comparing the nature and type of damage to the known available fuels at the scene

accelerant

in fire starting, any flammable fluid or compound that speeds the progress of a fire.

incendiary mechanism

may be mechanical or chemical, consists of; ignition, possibly timer, plants, and trailers

7. Why can items missing from the fire scene be as valuable as things remaining at the scene?

missing items or pets should raise the suspicions of the investigator

17. What are the minimum details that should be placed on an evidence container?

name of the person finding the evidence date location where found short description of the evidence item number case number and the evidence log number

16. What criteria should be employed in order to make a determination as to the types of containers that should be used for storage of evidence at the bomb scene?

the containers should be selected according to the type of evidence recovered and should afford sufficient protection to the materials that would permit their collection, storage, transport to the lab for examination, and subsequent use in any legal proceedings

claymore charge

uses explosive energy to propel shrapnel in one primary direction