Fire And Arson Investigation

Question 1

What is the leading cause of arson?

Answer 1

Vandalism

Question 2

Fire requires 3 elements

Answer 2

1. Heat
2. Fuel
3. Oxidizing agent

Question 3

What is fire a result of?

Answer 3

An oxidation reaction

Question 4

Oxidation

Answer 4

A chemical reaction between a substance and oxygen

Question 5

“Slow” oxidation reaction

Answer 5

Processes such as rusting or bleaching

Question 6

“Fast” oxidation reactions

Answer 6

Rapid release of beat such as combustion or fire

Question 7

“Extremely fast” oxidation reaction

Answer 7

Explosions

Question 8

Sequence of events during a fire

Answer 8

1. Incipient stage (growth)
2. Free-burning stage (development)
3. Smoldering stage (decay)

Question 9

Incipient stage (growth)

Answer 9

• begins with ignition of fire
• gases rise in the room
• oxygen dives to the bottom of the flames
• fire produces “V” pattern on vertical surfaces

Question 10

Free Burning Stage (development)

Answer 10

• fire consumes more fuel and intensifies
• flames spread up and out
• dense layer of smoke and fire gases accumulate near ceiling (carbon monoxide)
• at 1100F all fuels in the room simultaneously ignore (flashover)

Question 11

Smoldering Stage (decay)

Answer 11

• all fuel consumed and fire open flames disappear
• if oxygen enters, the spot and fire gases ignite with explosive force producing a backdraft
• pressure generated by a backdraft can cause significant structural damage and endanger lives

Question 12

Point of origin

Answer 12

• place where the fire started

* typically the site of greatest damage

Question 13

Backwards Theory

Answer 13

Investigators work from exterior to interior and from areas of least damage to greatest damage

Question 14

Burn patterns

Answer 14

Physical marks and char that remain after a fire

Question 15

Burn pattern geometry

Answer 15

Shapes on the walls or floors may indicate handling of accelerant

Question 16

“V” pattern

Answer 16

Accelerants from a container

Question 17

Hourglass pattern

Answer 17

Pool of burning liquid

Question 18

Pour pattern

Answer 18

Burn in the middle of a room

Question 19

Trailer pattern

Answer 19

Burn pattern that resembles s flowing stream; liquid was spread from one location to another

Question 20

Indicators of arson

Answer 20

1. Charring of floor surfaces
2. Containers
3. Odors

Question 21

Charring of floor surfaces

Answer 21

Area of burned floor adjacent to unburied floor is a reliable sign of liquid accelerant (“v” pattern)

Accelerant can often be detected in the corners of a room or along the base of a wall

Question 22

Containers

Answer 22

Liquid containers are evidence

If not damaged may be able to retrieve fingerprints left by arsonist

May indicate use of a liquid accelerant-even if melted

Question 23

Odors (from liquid accelerant)

Answer 23

May evaporate quickly so evidence must be collected immediately

Contaminated areas can be detected with ultraviolet violet light or a hydrocarbon detector

Question 24

Collection and preservation of arson evidence

Answer 24

Look for accelerant at the edges of burn pattern

Search for, identify, photograph evidence and note location in rough sketch

Photograph and comment condition of doors, windows, and locks

Collect debris in clean metal paint cans

Question 25

Metal paint and used for 2 reasons

Answer 25

1. Plastic will absorb compounds and may ruin sample

2. Cans are airtight and will preserve volatile vapors