Arson and BAC Review

Revised BAC

BAC - (time in hours x 0.015)

gas chromatograph

In the laboratory, the ___ _______________ is the most sensitive and reliable instrument for detecting and characterizing flammable residues.

control specimens

It is important that a sampling of similar but uncontaminated ________ ___________ be collected.

Pour Patterns

pool of ignitable liquid which can leave an irregular pattern

pyrolysis

A solid must be hot enough to decompose into gaseous products. (When heat converts solids and liquids into gas)

thermal plume

as gases are heated and become buoyant they flow upward and form a _______ ______

Victims of fire effects

carbon monoxide poisoning presence of soot pugilistic posture

Relevant Chemical Materials

criminalist's function is limited to detecting and identifying ________ _________ _________ collected at the scene and reconstructing and identifying igniter mechanisms.

Fire, gases, and smoke move because of

differences in temperature, density, and pressure

True arson indicators

multiple points of origin Trailers: combustible material used to spread fires Ignition device evidence of other crimes accelerant containers eye witness ignitable liquids

% of alcohol in drink(s) =

proof / 2

Fire induced injuries can cause:

pugilistic posture can cause breaks in joints muscles can contract enough to break bones Skull can fracture due to the heat

Crazed glass

rapid cooling of glass can cause small fractures.

Collection Procedure

should be collected and stored in airtight containers, leaving an airspace to remove samples.

Flashover

spontaneous ignition without a spark or flame.

80% proof

standard (14 grams)

Backdraft

sudden increase in oxygen after the fire starts to extinguish

what starts a fire?

the combination of oxygen and fuel gases

what would happen in a closed room without an outside air supply?

the oxygen in the room depletes and combustion stops

Alligatoring

the pattern of crevices formed by the burning of a wooden structure. Burns so hot, material forms blisters.

Heat

the thermal energy that produces fuel gases and causes ignition

ceiling jet

thin layer of hot gases spread along the ceiling

Synthetic and man-made fuels

type of fuel that releases the most smoke and can generate the most soot

legal limit of BAC

0.08

r for females

0.55

r for males

0.68

Fire Scene Procedures

The arson investigator needs to begin examining a fire scene for signs of arson as soon as the fire has been extinguished.

hydrocarbon components

The gas chromatograph separates the _________ ____________ and produces a chromatographic pattern characteristic of a particular petroleum product.

heat of combustion

The heat involved when a substance burns is known as the.

fire's origin

The search of the fire scene must focus on finding the ______ _______.

Petroleum

The vast majority of arsons are initiated by ___________ distillates such as gasoline and kerosene.

Glowing combustion or smoldering

________ ________ or _________ is burning at the fuel-air interface, such as that of a cigarette.

Spontaneous combustion

(rare) the result of a natural heat-producing process in poorly ventilated containers or areas.

Alcohol consumed (grams) =

(total mass of the drink (grams) x % of alcohol in a drink) / 100

igniters

A search for __________, such as matches, an electrical sparking device, or parts of a "Molotov cocktail" must also be conducted.

To initiate and sustain combustion, the following is required:

1. A Fuel must be present. 2. Oxygen must be available in sufficient quantity to combine with the fuel. 3. Heat must be applied to initiate the combustion, and sufficient heat must be generated to sustain the reaction.

Four Stages of Fire Development

1. Ignition (heat, oxygen, and fuel combine to create fire) 2. Growth (fuel will continue to burn as long as oxygen is available) 3. Full Development (all combustible items are ignited with enough oxygen) 3. Decay (longest stage when fire goes out)

1 lbs = _____ grams

454

gaseous state.

A fuel will achieve a reaction rate with oxygen sufficient to produce a flame only when it is in the _______ _______

flash point

A liquid burns when the temperature is high enough to vaporize it.

Arson

A perpetrator that has thoroughly planned a fire, is not present during the act, and the destruction is extensive.

BAC formula

Alcohol consumed (grams) ------------------------------ x 100 = Body Weight (grams) x r

Spurious arson indicators

Alligatoring Narrow V pattern Crazed glass pour patterns spalling of concrete melted metal

rate or speed

An additional factor needed to explain fire, besides the liberation of energy, is the ____ __ ______ at which the oxidation reaction takes place.

Collection of Evidnence

At the suspected point of the origin of a fire, ash and soot, along with porous materials that may contain excess accelerant

chromatographic peaks

By comparing select gas _____________ _____ recovered from fire-scene debris to known flammable liquids, a forensic analyst may be able to identify the accelerant used to initiate the fire.

V Pattern

Could indicate where the fire started (V-shaped)

petroleum-based accelerants

Experience shows that most arsons are started with

Rollover

Gases ignite, rise, and set the ceiling on fire.

ignition temperature

To start a fire, the minimum temperature needed to ignite fuel spontaneously must be reached.

vapor detector (sniffer)

Traces of flammable liquid residues may be located with a _____ ________

The necessity to begin an immediate investigation takes precedence even over the requirement to obtain a search warrant. T/F

True

Spalling of Concrete

Under intense heat, parts of the concrete fall.

Continuous pumping of fresh air can cause

flashover

when the ceiling jet reaches the walls, a hot gas layer forms and pressure __________

increases

Effect of ventilation

introduces new oxygen sources and can cause the fire to grow

Fire

is a type of oxidation, which is the combination of oxygen with other substances to produce new substances.

Ventilation

is the exchange of hot fuel gases and air in which hot gases flow out (exhaust) and cooler air enters (intake)

Conduction

is the movement of heat through a solid object.

Radiation

is the transfer of heat energy by electromagnetic radiation.

Convection

is the transfer of heat energy by the movement of molecules within a liquid or gas.