Arson & Explosions Arson and Explosions Chapter 14

According to the FBI Crime Index, juvenile and adult arson cause an annual average of 560,000 fires, 750 deaths, 3,700 injuries, and $1.5 billion in property loss. 55% of all arson arrests in the US are children under 18.

Source: Crime concealment Revenge or spite Monetary Gain Malicious Vandalism Mentally Disturbed Motives for Arson?

What is Fire? Oxygen combines with something to produce heat and light (Oxidation Reaction) EX. CH 4 + 2O 2 CO 2 + 2H 2 O+ Energy Reaction is Exothermic More energy released than needed to break bonds Not all oxidation reactions result in flames! – rusting – metabolism Chemicals that supply oxygen are known as oxidizing agents (O 2, H 2 SO 4 )

What are the ingredients to make fire?

Fuel= combustible material in any state of matter - solid, liquid, or gas. Most solids and liquids become a vapor or gas before they will burn. FUEL OXYGENHEAT

FUEL OXYGENHEAT The air we breathe is about 21% oxygen. Fire requires an atmosphere with at least 16% oxygen.

FUEL OXYGENHEAT Heat is the energy necessary to increase the temperature of the fuel to a point where sufficient vapors are given off for ignition to occur.

Stages of Fire of Fire

Incipient Stage Ignition via match, lightning, magnifying glass or spark Increase in temperature Fuel either on fire or smoldering

Ignition Temperature –Temperature a substance needs to reach before it begins to burn –The heat from burning causes further oxidations which causes further burning Gasoline 536 Degrees F Turpentine 488 Degrees F Kerosene 410 Degrees F Accelerant: any material used to start or sustain a fire.

Growth Stage Temperature increasing Fire grows slowly or fast depending on factors like fuel and oxygen “Fire feeds fire”; An 18 Degree increase in temp doubles and triples rate of reactions Oxidation reactions Hazardous toxic gases produced

What Is Really On Fire? Solids vs. Liquids vs. Gases More chance of collisions in gas form=more chance of chemical reactions Gases Ignite

Full Development/Active Fire Stage Flashover begins this stage= –Simultaneous ignition of all combustibles –Occurs when items are rapidly heated to pyrolysis temperatures Flashover – –“Raging” Fire

Volatile Gases burning rich in H, C, O Rising Carbon=Soot At base will be “Char”=Pure Carbon (Solid) Also have Ash=Nonburnables (Ca,K etc.)

Full Development/Active Fire Stage: Backdraft near the end of this stage –Often explosive event –Sudden feed of Oxygen Via window opening or roof collapse –Sudden flash combustion of remaining fuel –BackdraftBackdraft

Decay Stage Fuel Diminishes and/or Fire Fighting Successful Temperature decreasing Still may smolder

Spontaneous Combustion Burning resulting from natural heat-generating reactions –Ex. Hay and heat-producing bacteria –If no ventilation, heat builds to combustion –Ex. Oily rags –Slow accumulation of heat from oils oxidizing with air

Fire Scene Search Search immediately without warrant-Fire Marshal Scene Processing: 1.Work from low damage area to high charring 2.Document and Interview Witnesses 3.Look at ceilings-Point above origin has most damage from longest exposure 4.Look at light bulbs-they bulge when exposed to 900 degrees F for 10min (Side that bulges point towards origin 5.Soot on glass=slow smolder burn 6.Cracked glass=hot fire 7.Color of flames=Tells what temperature was fire 8.Color of smoke=Tells what was burning 9.Collect Samples

Fire Scene Search-Fire Origin V-pattern charring above point of origin Wind can distort the Vs

Frig. Fire Yellow- V Red- Origin Green-Debris “drop down” analysis.htm

Stove fire

Electrical Fire??? Your thoughts… analysis.htm

V-Patterns - Fire burns up, in a V-shaped pattern, so a fire that starts at an outlet against a wall leaves a char pattern that points to the origin. –Narrow V= hot fire helped along by maybe an accelerant. –Wide V= maybe slow burning fire. – U-shape= "pool of origin” maybe a puddle of gasoline

Char Patterns – Created by very hot fires that burn very quickly and move fast along its path, so that there can be sharp lines between what is burned and what isn't. –A char pattern on a door would help an investigator determine which side of the door the fire was on. –A char pattern on the floor would help investigators determine the use of an accelerant and its path.

Char Patterns and Accelerant Use Often characterized by intermixed light, medium, and heavy burning in a puddle shape that corresponds to the shape of the original pool of the ignitable liquid.

Photos provided by Brock Brooks & the Havana Fire Department Havana – Laurel Street Practice Burn Photographs What clues might a fire investigator gain from this photograph?

Photos provided by Brock Brooks & the Havana Fire Department Havana – Laurel Street Practice Burn Photographs

A fire started in the kitchen area does not take long before it is a ball of flame reaching quickly to the ceiling. Fires can easily double in size every 60 seconds, meaning there is little time to extinguish a fire before escape should be your primary goal if trapped. Fire fighters look on as the fire spreads across a room. The house is nearly completely consumed. Source: Practice Burn Photographs

Accident or Arson? Accidental Nature –Heating System –Electrical appliances –Lightning –Children playing with matches –Smoking Image: Havana Rural Fire Department

Signs of an Arsonist Signs of Break-in Ignition Device Streamers or Trailers to spread

Clues to Arson Fire spreads upward and outward (“Chimney Effect”) –If it goes downward from origin, it is strange

Clues to Arson Charring on floors and even under furniture and appliances is abnormal (probable accelerant)

Clues to Arson Odors – Gas, kerosene, or other accelerants Two or more points of origin Look for inverted v-patterns (can be a sign that an accelerant was used) Room floors usually don’t burn (below ignition temp) Room corners and edges don’t burn (low air areas) No personal effects (Insurance fraud) Holes in wall Doors propped open All Drapes closed

Tools of Investigator “Sniffer”=Vapor Detector Arson Dog

Problems for Investigator Perp long gone Evidence destroyed –Burnt –Wet

Good News Accelerants might seep into protective cracks in floor and wall Might have seeped into rugs, upholstery, rags etc. Accelerant mixed with water from firemen will slow evaporation

Evidence Collection 2 to 3 quarts of ash from origin Collect suspicious rug, floor, cloth samples Collect control samples Package in airtight tin can containers fill cans 2/3 full (top space for gas analysis) Don’t use plastic bags since they react with vapors

Evidence Processing Heat evidence container to volatize any remaining liquids Vapors exit through a tube in can Gas Chromatography-MS

Gasoline Residues Unevaporated gasoline 90% evaporated gasoline Unevaporated kerosene 90% evaporated kerosine*

Connect to Arsonist On suspect –Match book –Clothing has residue

Court

Explosions Motivation: Terror Individual Revenge –Destroy people –Destroy property Mischief Accident (gas leak)

What is an explosion?

Explosion Physical Explosion: =mechanical action resulting in the rapid expansion of gases =Kinetic energy released

Chemical Explosion= fast reaction to produce heat, light and gas expansion (Kinetic and Thermal Event) “Energetic Materials” release lots of energy in a short time from a compact volume of material

Evidence Collection Powerful explosions leave craters 1,000 pound explosive crater

Damage from High Explosives Shock Wave Heat Flying Debris

Materials

Evidence Collection CSI members wear bunny suits to prevent contamination Collect crater soil samples for explosive residue Examine soft objects (wood, insulation, rubber etc.) near origin for residue

Piecing together bombings Pan Am Flight 103

TWA Flight 300

USS Cole in Yemen lbs of Explosives

London Bombings

EGIS Vacuum captures vapors High speed chromatography of vapors Screens for explosive residues

Analysis Microscopic examination for traces of explosive powders (Visual) Dissolve powder in acetone –Color Test –TLC –HPLC –GC-Mass Spectrometry

Evidence Storage Metal Cans Avoid plastics since vapors can escape plastic bag

Taggant Program Color-coded chips added to explosives Florescent and magnetic Has data of origin and date of production