Module 3 - Arson and Explosives

Module 3 - Arson and Explosives

Arson is the crime of setting a fire for an unlawful or improper purpose. It is a problem because it costs hundreds of millions of dollars annually in increased insurance costs, increased taxes, loss of jobs, loss of business revenue, and treatment of injuries. Arson differs from other crimes in that it is not immediately obvious that a crime has occurred. It is a difficult crime to investigate because the fire frequently destroys evidence. Despite this, numerous telltale clues are often left behind an arson fire that can help investigators find the culprit.

Arson is a relatively easy crime to commit because a fire is easy to light. A small fire quickly becomes a big fire if it is not controlled early. Therefore, the amount of damage caused by an arsonist usually depends on the amount of time that lapses before firefighters arrive.

Explosions occur less frequently than arson fires. The likely reason for this is that, for the most part, creating an explosive device is more difficult than starting a fire, and starting a fire requires very little planning and effort. Law enforcement officers have several unique ways to investigate crimes involving an explosion.

Organization of the Module:

• Lesson 1 examines the nature of a combustion reaction and the motives and profile of an arsonist.
• Lesson 2 outlines the various methods used to investigate arson fires.
• Lesson 3 describes the various types of explosives and identifies some explosive detection techniques.
• Lesson 4 examines the details of two historical crimes that involve arson and explosives.

Module Learner Objectives

By the end of Module 3, you should be able to…

• identify the components necessary for a combustion reaction
• explain how combustion differs from an explosion
• understand the terminology that relates to arson (such as accelerant, blast, booster, detonation, endothermic, exothermic, fuel, ignition, pyrolysis, oxidizer)
• describe the three points and conditions of a fire: flash point, flammable range, and ignition range
• describe the level of oxygen needed to keep a fire burning and the various products of a combustion reaction that can cause a fire to continue
• describe arson and determine the various types of arson by the severity of the damage caused
• identify various motivations for arson and possible strategies to eliminate this crime
• recognize the steps in the investigative process of a possible arson
• identify various tools and methods used in arson investigations (such as portable arson sampler, chromatography, lasers, solid-phase microextraction, arson profiling, metal oxide sensors, canines, photoionization detectors)
• compare the numbers of human fatalities and human injuries caused by arson using graphed data
• compile and present various data related to arson (such as local statistics, common motives, profile of typical arsonist, child arsonists, total cost of arson investigations, arson prevention methods)
• identify the three basic components of an explosive device: fuel source, oxidizer, and ignition.
• identify and describe various types of explosive devices (including gunpowder, dynamite, nitroglycerin, saltpetre, guncotton, TNT, PETN, picric acid, plastic explosives)
• describe various devices or techniques used by forensic experts to detect explosives (such as robots, EGIS, canines, X-rays, metal detectors, ion mobility spectrometry, honeybees)
• recognize various types of explosives (such as explosive bombs, chemical bombs, inert bombs, nuclear bombs) and understand the function of each.
• explore a historical crime case(s) involving arson and/or explosives (such as Timothy McVeigh, Frederick Small, U.S. Embassy in Kenya, Pan Am Flight 103, 9/11 World Trade Center Disaster, Unibomber).

Combustion

A fire is the result of a chemical reaction called combustion and is based on the principles of oxidation. In an oxidation reaction, energy is produced in the form of heat, light, noise, or a combination of these. To start a fire, three things must be present: fuel, oxidant, and heat source.

Fuel in Combustion Reactions

An accelerant is commonly used to start an arson fire. An accelerant is a liquid or solid fuel source that increases the rate of combustion. An accelerant allows the fire to burn at a higher temperature with an increased rate of spread.

Often arsonists use hydrocarbon-based fuels as accelerants, especially ignitable liquids such as gasoline, diesel fuel, kerosene, turpentine, or butane. The combustion of an ignitable liquid actually happens in the gas phase because the liquid does not actually burn. To ignite, a liquid must be heated to its flash point, the specific temperature at which it changes to a gas and burns.

Ignitable liquids are dangerous accelerants. Given the right circumstances, they ignite easily and can readily explode. Consequently, arsonists who use large amounts of liquid accelerant to start their fires may suffer serious injuries or death.

Ignitable liquids leave very distinctive burn patterns in the fire debris. To the trained eye, these irregular burn patterns can indicate the presence of an ignitable liquid in a fire.

Some accelerants used in arson fires are solid fuel sources such as common household items that contain wicker, foam, paper, or wood. Using large amounts of solid fuel tends to increase the rate of fire growth and spread the fire over a much larger area, thus increasing the amount of damage.

To determine whether arson was the cause of a fire, investigators look for the presence of accelerants in the debris of the fire. In addition, unusual quantities or types of accelerants can indicate arson, especially when detected in unusual area(s).

Oxidants in Combustion Reactions

In combustion reactions, the oxidant is oxygen gas. The simple word equation for combustion in the presence of oxygen is

fuel + oxygen -> energy + water + carbon dioxide

In most combustion reactions, the necessary oxygen is available in the surrounding air. The air in Earth’s atmosphere contains oxygen as well as a mixture of gases: 78% nitrogen, 21% oxygen, 0.93% argon, 0.04% carbon dioxide, trace amounts of other gases and water vapour.

The Products of Combustion

As a substance burns (undergoes combustion), a complex sequence of exothermic chemical reactions occurs. An exothermic reaction produces heat energy and often light energy as well. When light energy is produced, a flame or glow is visible.

Water and carbon dioxide are also produced during combustion reactions. The water is visible as gas (steam) because of the high temperatures associated with this type of reaction. Carbon dioxide is invisible.

Speed of Ignition

Ignition occurs when the heat produced by the reaction between the fuel and oxygen becomes sufficient to sustain combustion. Three terms are used to describe a fire’s speed of ignition: flash point, ignition range, and flammable range.

• The flash point is the lowest temperature at which enough vapour is produced to permit ignition. The lower the flash point, the greater the risk of fire. The flash point can be reached only if enough fuel, oxygen, and heat are available to support a combustion reaction.
• The ignition range is the temperature at which a combustion reaction can sustain itself without the addition of more fuel or oxygen.
• The flammable range is the relatively high temperature at which ample amounts of fuel produce flames.

The speed of the reaction is determined by how quickly combustion moves through these three ranges. Increasing the temperature can double or even triple the reaction rate.

For a fire to remain ignited, it must have oxygen. If oxygen levels fall below 16%, most fires will extinguish. However, depending on the material(s) being burned, the chemical reaction in a fire can produce substances that contain oxygen; which allows the reaction to continue. For example, burning wood produces carbon dioxide (CO₂), carbon monoxide (CO), sulphur monoxide (SO), nitrogen monoxide (NO), and water (H₂O). The oxygen released from these gases can continue a fire in the absence of air or oxygen gas (O₂).

Arson is the intentional burning of private or public property. Half of arson fires are set outdoors (such as wooded or grassy areas, parks, construction sites), 30% are set inside houses or other buildings, and 20% involve vehicles. Vacant and abandoned buildings are often targets for arsonists. Arson incidents are fourteen times more likely in poor neighbourhoods than in high income neighbourhoods.

Sometimes arsonists target forested or grassy areas. Such uncontrolled fires have a number of different names usually depending upon which type of vegetation is set on fire (such as forest fire, grass fire, peat fire, or bushfire). Often these wildfires get out of control and destroy nearby houses or agricultural resources. Heat waves, droughts, and high winds can dramatically increase the size of the area consumed by a wildfire.

Motives for Arson

The motivations for committing acts of arson vary. Psychiatrists and social and behavioural researchers have found five main motivations for arson. These are revenge, excitement, vandalism, crime concealment, and financial profit.

Arson for Revenge: The majority of arson crimes are acts of revenge. The incident that causes an arsonist to seek revenge may be real or imagined and often occurs months or years before the arson.

Disagreements or feelings of jealousy are common causes of this crime. Revenge arson is focused often on an individual’s home, property, or place of business. However, domestic violence is also a common cause of revenge arson. The goal of the culprit in this case may be to cause personal injury or to commit murder. Disgruntled young arsonists often will set fire to school property. This type of arson tends to be well planned, and the culprit’s attempt to conceal his or her identity is often ineffectual.

Cases of revenge-seeking arson fires have also been documented as being started by firefighters hoping to injure a superior or co-worker. In these cases, the disgruntled firefighter usually is extremely angry because he/she has lost his/her job or has had grievances or complaints filed against him/her.

Arson for Excitement: Sadly, the second leading motive of arsonists is simply the need for excitement. Boredom, the need for attention, and the enjoyment that the arsonist gets from watching firefighters fight the blaze are all possible compounding factors. In these cases, the targets tend to be large and often outdoors (such as wooded areas, parks, construction sites, arenas). Sometimes these arsonists target a number of homes in a residential area (such as garages, backyards, dumpsters). Usually, this type of arson occurs at night and the arsonist is intoxicated at the time of the offense.

Some arsonists set fires because they are excited by the prospects of being seen as heroes. After these arsonists set fire to their targets, they attempt to rescue endangered people or try to extinguish the fire. The "hero effect" is often a desire of firefighters who are bored by a lack of fires or are seeking attention for their supposed bravery.

Arson for Vandalism: The third leading motive of arson is vandalism. This type of arson tends to be caused by two or more male juveniles who set the fire together. Reasons for these youngsters to commit such crimes include family difficulties or peer pressure from ‘friends’. Targets in these cases are often vacant or abandoned buildings. Fire departments must respond to there fires promptly and aggressively out of concern for any transient or homeless people that may be inside. Sometimes arson vandals are brazen and will attack non-vacant buildings such as schools, homes, or churches.

Arson for Crime Concealment: Crime-concealment arsonists set fire to places in which they have committed crimes in an attempt to destroy evidence that might implicate them or prove that crimes have occurred. The crime that such an arsonist tends to conceal is burglary, but sometimes it can be a murder. Such fires are usually set at night in unoccupied homes or places of business.

Arson for Profit: Interestingly, arson motivated by profit is the least common motive for arson. In these cases, the possibility of financial gain drives an arsonist to set fire to his or her own property (home or business) with the intention of filing a fraudulent insurance claim afterwards. Arson for profit is usually committed by adults and rarely is committed by juveniles because they seldom own any property. Very often, the arsonist in these cases is under extreme financial pressure. In general, such fires tend to occur during the day in unoccupied homes or other buildings.

More than 90% of arsons are committed by males, the majority of which are under the age of 18. Usually those arsonists who are under 18 have also been charged with property offences in the past. Those few females who have committed arson are most often motivated by revenge. Adult male arsonists tend to be under the age of 35 and their motive for arson is often for revenge or for profit.

A great number of male arsonists tend to have interpersonal problems with females. They tend to exhibit a lack of remorse especially when they are setting a fire often because of their dissociative trance-like states.

Most arsonists are from lower to working class families. Arsonists who have a middle class background tend to commit arson for vandalism or excitement. Often arsonists have absentee or abusive fathers and a history of emotional difficulties with their families.

About 90% of arsonists have only a high school education or less. The majority of arsonists have IQs slightly below average; 22% are considered to be developmentally delayed. In school, arsonists usually have had learning problems and often were held back a grade—usually in grades 6, 7, 8, or 10.

Arsonists that set a fire for excitement, vandalism, or profit tend to be unemployed. Those that are employed tend to be in subservient positions that they resent.

Young Arsonists

Most of these young arsonists (juvenile males under the age of 18) begin exhibiting interest in fire between 3 and 10 years of age. Motives for young arsonists include boredom, curiosity about fire, accidents, peer pressure, or expressions of anger and stress. A fire deliberately set by a young child usually considered an accident or a result of misbehaviour instead of arson. Depending on the motivation behind the fire setting, how the child is disciplined and/or counselled can have a profound impact on whether or not that child continues to set fires as a teenager or adult.

Fires set by children are usually located in or near the family home. If a child arsonist extinguishes the fire before it gets out of control they often will feel remorse for their actions and try to conceal any related evidence. Child arsonists often stop their behaviour when counselled by an adult. When a child who sets fires is not helped to change, he or she can develop into a teenage arsonist. Teenage arsonists often have an average intelligence, but they exhibit poor academic progress due to learning difficulties or behavioural and/or psychological problems. They often commit their crimes to seek revenge or as responses to traumatic events such as divorce or death. Setting fires becomes an outlet for their troubled emotions.

Recognizing and identifying children who set fires deliberately is important because their behaviour often may be modified through counselling. Even if a child is not a problem fire setter, parents should teach and establish rules regarding fire safety.

Background:

Data collected each year related to the causes of various arson fires helps to determine if the strategies for arson prevention are effective. The statistics in this activity concern the causes of home fire fatalities in Alberta over a five-year period.

Problem:

What are the causes of fatal home fires in Alberta from 2001 to 2005?

Procedure:

• Use the data in the table below to create a bar graph.
• Label the x-axis with the causes of fire.
• Label the y-axis with the total number of deaths.
• Incorporate a title and a legend into your graph.

Causes of Fatal Home Fires in Alberta (2001 – 2005)

Related Questions:

1. What were the top three leading causes of fatal home fires in Alberta from 2001 to 2005?
   
   Ans. The top three leading causes of fatal home fires were:

   1. Smoking
   2. Arson
   3. Cooking and Electrical wiring (tie)

2. What percent of the total deaths was the result of arson from 2001 to 2005 in Alberta?
   Ans.  The percentage of total deaths caused by arson from 2001 in 2005 in Alberta was 9.7%.

3. Arson is a deliberately set fire. Explain what other cause of fire could also be considered to be a deliberately set fire.
   Ans.  Child fire play is a fire deliberately set by a youngster. Most often, it is considered an accident or misbehaviour.

Arson is difficult to solve because arsonists are usually careful to avoid eyewitnesses and often much evidence is destroyed. Investigators must discover evidence in the ash and debris left by the fire. This evidence is often circumstantial, meaning that facts support the evidence but no conclusive proof is available.

The successful arrest and prosecution of an arsonist involves extensive investigation of circumstantial evidence. Prosecutors are willing to accept this type of evidence and are committed to taking these circumstantial cases to trial.

A Forest Fire Burning at Night

- Image Source: Wikipedia

Obviously not all fires are caused by arson. In fact, most fires are accidental. The single, most common human cause of fires is careless smoking. Certain telltale signs indicate that an arson fire has occurred.

Fire investigators look for these signs when they first arrive upon a fire scene:

• Multiple points of origin
• Point of origin near a good supply of oxygen (such as an open window)
• Evidence that fire burned quickly and for a relatively long time
• Empty fuel cans or other evidence of the use of accelerants
• Unusual odours caused by the use of accelerants

To ensure fire safety, all building products, materials, and furnishings in North America must be tested for fire resistance, combustibility, and flammability before they can be used in construction. The same applies to upholstery, carpeting, and plastics used inside vehicles.

Four Areas of an Arson Investigation

To prove that arson was the cause of a fire, investigators look for evidence in the following four areas:

1. Proof of Incendiarism:  Fire investigators classify the cause of a fire as natural, accidental, unknown, or incendiary. An incendiary fire is one deliberately set by an arsonist. To classify a fire, investigators first try to locate the origin of the fire. To do this, photographs and diagrams of burn patterns are made and physical evidence is collected and analyzed at the fire scene. The origin of the fire along with other physical evidence can help determine the cause and the approximate time the fire was ignited.
   
   
2. Proof of Opportunity:  To identify suspects in arson investigation, fire investigators consider everyone who had opportunity to set the fire. They examine building security. Everyone with access to the site before the fire is asked to provide an alibi for the period of the fire. If all alibis are confirmed, investigators conclude that the arsonist must have gained access to the site illegally; consequently, other evidence must be used to identify the suspects(s).
   
   
3. Proof of Motive:  Arsonists set fires for several reasons, such as financial gain, revenge, crime concealment, or vandalism. An owner may become a suspect if he or she gained financially from properties destroyed by fire in the past or if he or she is having financial difficulties and stands to gain from an insurance claim for the property under investigation. Investigators examine the owner’s current insurance policies, insurance history, and current financial situation.
   
   
4. Circumstantial Evidence:  Because the evidence related to arson is often circumstantial, investigators collect as many different types of evidence as possible to support their case. Following is a list of several types of evidence that investigators may use to support their case:
   • On-site fire or burglar detection systems are inspected for evidence of malfunction or tampering.
   • If the fire was reported, the identity of the caller is determined and a background check is completed.
   • The license plates of automobiles in the area surrounding the fire may be checked.
   • Previous police activity conducted in the area is reviewed, as well as any reports of vandalism.
   • Hospitals in the local area may be asked if any patients with fire-related injuries were treated soon after the fire was set.
   • If an accelerant is identified, investigators may question local gas stations or hardware stores to see if a similar accelerant (such as gasoline or paint thinner) was purchased locally.

Indoor Fire Scene Investigation Tasks

After a fire has been extinguished and arson investigators can safely enter the site, access to the fire scene is controlled by police and fire department personnel to avoid scene contamination.

Arson investigators create an evidence collection area near the fire scene where they store any physical evidence found. Furniture, appliances, and other materials are often placed back in their pre-fire positions using the maps drawn by the occupants. This helps investigators examine and document every potential accidental ignition source or origin of arson in the rooms. In general, fire will burn longer at or near the point of origin. Therefore, damage will generally be more severe at the point of origin. Often physical evidence of the cause of the fire is found at or near the point of origin.

When the origin of the fire has been determined, a detailed diagram of the site is drawn. Windows, walls, floors, doors, ceiling composition, and the locations of key items are noted. All the entrance and exit points with lock types and conditions are identified. Sometimes, investigators call in experts to inspect and examine electrical wiring, appliances, or furnaces.

An interpretation of burn patterns may help investigators determine the cause and origin of a fire. Three burn patterns that are often identified during an arson fire are the classic V, the doughnut, and the ignitable liquid pour. Examination of burn patterns may reveal important information regarding the cause of the fire.

- Image Source: Robert A. Corry Director, Fire Investigation Specialist

Classic V pattern: As a fire moves upwards on a vertical surface, it creates a distinct V pattern. The most severe physical damage is usually found at the bottom of the V pattern. Because this is likely the point of origin, investigators focus their investigation on this area for evidence of accelerants or other possible causes of the fire.

Doughnut pattern: When a liquid accelerant is poured on carpet and lit, it tends to create a circular ‘doughnut’ type pattern. After the fire has been extinguished, evidence of accelerant is often found inside the ‘doughnut’ because the melted carpet material in the doughnut interior protects the carpet padding (which is saturated with fuel) from the effects of the fire.

- Image Source: Robert A. Corry Director, Fire Investigation Specialist

Ignitable liquid pour pattern: Intense burn patterns are caused by ignitable liquid hydrocarbon accelerants such as gasoline, kerosene, or diesel that have high boiling points. When hydrocarbons burn, they tend to cause physical damage and distinct dark-coloured patterns (see photograph above). Accelerants with high vapour pressures, such as alcohol, acetone, and paint thinner, tend to ‘flash and scorch’ surfaces. Therefore, they cause less physical damage and more superficial scorching.

- Image Source: Robert A. Corry Director, Fire Investigation Specialist

When an ignitable liquid fuel source has been used to start a fire, intense burn patterns often appear on the areas where the liquid has been poured directly. Dark-coloured burn patterns tend to occur at the lower locations of uneven surfaces where fuel may have pooled before it ignited. These burn patterns are especially common on nonporous surfaces such as linoleum floors, tiles, and laminates. When an ignitable liquid fuel is poured onto porous surfaces such as carpets and wood floors, it may be absorbed into the materials as well as wood joists below the floor creating dark, distinct rundown burn patterns as shown in the photograph above.

Painting of the Great Chicago Fire, 1871

- Image Source: Wikipedia.org

The physical evidence collected from a fire scene is analyzed and interpreted by forensic lab specialists. These forensic experts use specialized scientific equipment or techniques to help determine the cause of the fire. The most common service provided by laboratories to fire investigators is the analysis of fire debris for suspected accelerants. Arsonists often use an excess of accelerant to start a fire. Accelerant residues remain, and they may be detected by laboratory analysis. Unfortunately, if only a small amount of accelerant is used or if the accelerant is poured onto highly flammable substrates such as paper or plastic, laboratory analysis may be ineffective because no residues are left in the debris.

The appearance of a flame under normal gravity conditions depends on convection. As soot rises to the top of a flame, it is cone-shaped and appears yellow. In zero gravity, such as in outer space, convection no longer occurs, and the flame appears round, spherical, and blue.

Collection of Evidence from a Fire Scene

Proper collection and storage of evidence is crucial to ensure that evidence is not contaminated. The ideal containers for fire scene evidence suspected of containing volatile accelerants are clean metal paint cans, sealable glass jars, or plastic bags. Fire investigators use several unique ways to find and collect physical evidence.

After evidence from a suspicious fire scene has been collected, forensic experts analyze it in laboratories.

In most cases, arson investigators try to confirm if an accelerant was used and the type of accelerant used. Specific identification of accelerants used in arson fires is a challenging task. Often the accelerant can be detected and identified. However, at times an accelerant cannot be detected because all traces of accelerant were destroyed by the fire.

During the 1980s and early 1990s, a string of baffling arson fires in Southern California, USA, took the lives of four people and caused more than several million dollars damage. The identity of the person responsible for these horrendous crimes was a shock to everyone.

On an afternoon in October 1984, a major fire occurred in a hardware store in South Pasadena, California, USA. The store was completely destroyed and four people, including a two year-old child, died in the blaze. All but one of the fire investigators assigned to the case thought the cause of the fire was faulty electrical wiring. The one fire investigator who disagreed was John Orr, the Captain of the Arson Unit with the Glendale Fire Department. Orr insisted very early in the investigation that the cause of the fire was arson. Although initial findings did not support Orr’s assumption, further investigation revealed that the fire was started by an expert in fire setting. The arsonist started a small fire in an area of the store in which polyurethane products such as varnish and glue were stored. Because of the highly flammable nature of these products, the fire spread so quickly that four people died. The arsonist was not caught, and as time passed, more fires were set.

The next series of fires set by the arsonist occurred during January 1987 in Los Angeles. No one was killed or injured in these fires, but they caused thousands of dollars damage. Each fire occurred in the middle of the day at various businesses and each was started with a time-delayed device. Ironically, the fires were set during a major arson investigators conference in nearby Fresno, a city near Los Angeles. Luckily for investigators, a fingerprint on a small piece of paper inside a small time-delay explosive device was discovered at one of the fires. However, the single print could not be matched to any criminals in the fingerprint database that investigators used. Evidently, the suspect had no criminal record.

In March 1989, another four arsons occurred in various cities along the southern California coast. Yet again, the arsons were caused by time-delayed devices and they occurred the same time as a conference of arson investigators in nearby Pacific Grove. This raised suspicions that the culprit was possibly an arson investigator from the Los Angeles area. Working with this assumption, investigators compared a list of attendees from the Fresno conference with the list of attendees from the Pacific Grove conference. By April 1991, a short list of ten suspects was compiled. Each suspect was asked for fingerprints. All the arson experts on this short list except Captain John Orr of the Glendale Fire Department were cleared of suspicion when their prints were compared with the fingerprint from the Fresno fire.

Orr then became the subject of an intensive investigation and surveillance until his arrest. Investigators installed a tracking device behind his dashboard when he had his vehicle serviced in November 1991. Shortly thereafter, in December 1991 when Orr was tracked to the scene of another suspicious fire before dispatchers were made aware of the blaze. The surveillance ended, and an arrest warrant was obtained.

Bizarre pieces of evidence used to convict John Orr included

• secret videotapes taken by Orr of suspicious fires including those he was accused of starting
• an unpublished manuscript written by Orr about a serial arsonist who is a fire investigator (This manuscript contained detailed descriptions of many of the fires Orr was accused of setting.)

In July 1992, a jury found John Orr guilty of three counts of arson; he was sentenced to thirty years in prison. Orr adamantly maintained his innocence; however, he still pleaded guilty to three other counts of arson in March 1993. In June 1998, a jury convicted Orr of four counts of first-degree murder for the 1984 Fresno fire. As a result, he was sentenced to life in prison without the possibility of parole.

In 2003, a novel about John Orr entitled Fire Lover: A True Story was written by acclaimed crime novelist Joseph Wambaugh. This novel was later adapted into an HBO movie entitled Point of Origin in which Ray Liotta portrayed the serial arsonist John Orr.

Related Case Study Questions

1. In the deadly 1984 arson fire, was John Orr’s assumption correct about the cause of the fire? Explain.
   Ans.  Orr insisted very early that the cause of the fire was arson. Initial findings did not support Orr’s assumption. However, further investigation confirmed this and revealed that the fire was started by someone who was an expert in fire setting.
2. What piece of individualized evidence linked the culprit directly with the arson fire?
   Ans.  A fingerprint on a small piece of paper inside a small time-delay explosive device at one of the fires linked the culprit with the fire.
3. How did investigators create a short list of arson suspects?
   Ans.  Investigators compared a list of attendees from the Fresno arson investigation conference with the list of attendees from the Pacific Grove arson investigation conference.
4. What finally lead investigators to arrest John Orr?
   Ans.  Orr was arrested when he was tracked to the scene of another suspicious fire before dispatchers were made aware of the blaze.

Explosives

Explosives contain one or more chemical compounds that when detonated decompose or react very rapidly releasing gas, heat, and violent destructive shock waves. Detonation of an explosive device involves exposing the chemical compounds to heat or movement (mechanical shock or friction). Often explosives are placed within a metal casing that, when exposed to heat or shock, allows the pressure inside to increase until it bursts and fragments. The pieces of the explosive casing that blast outward at very high speeds are called shrapnel and can cause extensive damage to people, buildings, airplanes, vehicles, and anything else in the immediate area of the explosive blast.

An explosive device has an ignition source or a fuse that when ignited causes a reaction between the compounds in the metal casing. A fuse is simply a length of cord either filled with combustible material or made from combustible material. The length of a fuse determines its burn time. For example, a fuse 30 cm long will take 60 seconds to burn and then detonates the explosive. Some fuses detonate after set periods by using mechanical, electronic, or chemical timers. Other fuses are point-detonating fuses; they combust upon impact such as when dropped or thrown.

Some explosives have remote detonators that use wires or radio waves to detonate the explosive device from a distance. Bombs hidden in containers such as packages, suitcases, boxes, or portable stereos are usually triggered by battery-powered ignition switches (such as clocks) that are activated by opening the containers or by time-delay switches. Car bombs are usually detonated when the vehicle is started by the ignition switch. Usually, most of the time and effort that goes into making an explosive device is spent on the ignition source.

Inside the casing of an explosive, there is either a pure compound or a mixture containing an oxidizer and a fuel source. An example of a pure explosive compound is nitroglycerin, a highly unstable, heavy, colourless, oily liquid. Nitroglycerin is faster to ignite and more powerful than gunpowder. Nitroglycerin combined with sawdust makes dynamite. Dynamite is used for controlled blasting of dam sites, canal beds, and mines or demolishing large buildings by imploding their foundations.

Nitroglycerin

An oxidizer is a molecule that releases some atoms of one or more oxidizing elements allowing the fuel source of the explosive to continue burning. The fuel source of an explosive is an unstable chemical compound that when ignited produces an explosion. Two examples of oxidizer/fuel source mixtures found in explosives are the following:

• Black powder = potassium nitrate + charcoal and sulfur
• Flash powder = potassium nitrate + aluminum or magnesium

A fire and an explosion are often mistakenly considered to be the same thing. If explosive compounds are present where a fire is occurring, an explosion can occur. Heat and gas generated by an explosion often lead to a fire.

Differences between a Fire and an Explosion:

• An explosion is detonated. A fire cannot be detonated. An explosion occurs after compounds are exposed to heat or shock. A fire is initiated after being exposed to a heat source only.
• Because of how quickly the reaction occurs in an explosion, shock waves are produced. A fire does not produce shock waves.
• Explosives usually have less potential energy than combustible hydrocarbons, but explosives release energy at a higher rate, which produces a greater blast pressure.

Similarities between Fire and Explosion:

• Both require oxygen.
• Both require a fuel source.
• Both create heat and light.
• Both usually will damage the environment in which they occur

Categories of Explosives

For a compound to be considered explosive, it must react rapidly when exposed to heat or shock and it must produce gas and heat rapidly. An explosion is the oxidation and combustion of at least two unstable substances that produces a violent reaction.

Two general types of explosives are labelled high and low. Each is categorized by how quickly the explosive compound ignites and how fast the chemical reaction occurs. The speed of the chemical reaction that generates each type of explosion influences various other aspects of the blast.

Low explosives are sensitive to heat, friction, and temperature. The speed of the shock waves generated by a low explosive blast is approximately 2300 meters per second. Low explosive materials are usually lethal only when confined to a sealed container in which a huge increase in pressure occurs. Generally, explosives used in criminal activities are low explosives because they are small and are often created with easy-to-find materials such as fertilizer, gunpowder, or gasoline. Examples of low explosives include pipe bombs, car bombs, gunpowder, flares, and illumination devices.

High explosives tend to be larger, more complex, and more powerful. They also have a much greater speed of reaction than low explosives. Because high explosives react so quickly, the build-up of pressure and gas is almost instantaneous. High explosives tend to be less sensitive to heat, friction, and temperature. They create powerful shock waves that have speeds of up to 6900 metres per second. Examples of high explosives include compounds such as nitroglycerin and TNT. Both of these explosives are used for mining and demolition and are used in military warheads.

The location of explosive devices can be determined in several ways. The most common methods of explosive detection used today include bomb detection dogs, bomb detection robots, X-ray machines, and metal detectors.

After a bomb has been located, be it detonated or not, investigators must identify specifically the type of chemical compounds that caused or could cause an explosion. This information may help to identify the suspect(s) and/or help prove which suspect committed the crime. The two most popular methods used to identify explosive compounds involve gas chromatography and mass spectrometry.

Bomb Detection Dogs: Because a dog’s sense of smell is thousands of times better than a human’s, most police departments use specially trained police service dogs to identify the location of explosives. These dogs are trained to detect the odour of hundreds of different explosive compounds. They cannot identify the type of explosive. When a bomb detection dog detects an explosive substance, it is safely and carefully detonated.

Remote Mechanical Investigator: Remote Mechanical Investigator (RMI) units are robotic devices that are used to locate and safely remove explosive devices. An RMI is commonly used in situations where a bomb threat has been made or a suspicious package detected. In these instances, the area near the bomb is cleared to prevent human casualties. Several small cameras are mounted on an RMI to allow the operator to control its movements using a television monitor. The robot’s operator uses its extendable arm and oscillating hand to disarm, remove a bomb, and/or safely detonate a bomb. A RMI robot is expensive, and its use is often limited to large police departments.

X-ray Machines: Specially designed X-ray machines can detect and identify explosives determining the density of a suspicious object and comparing it to known densities of various explosives. These X-ray machines use special computer software to make positive readings. However, ultimately, the operator determines if the object contains an explosive. X-ray machines are used by some police departments, most airports, highly secure government facilities, and some schools.

Metal Detectors: Most explosives are contained within a metal casing. Therefore, a metal detector alerts its operators to the presence of metals—which might contain explosives. When this occurs, a suspicious object is then examined to determine if it is actually an explosive and not just a device that happens to contain metal. Similar to X-ray machines, metal detectors are also used by some police departments, most airports, and highly secure government facilities, and some schools.

EGIS: Erieye Ground Interface Segment, a military software package, is a highly accurate device that uses gas chromatography and mass spectrometry to detect the presence of plastic, commercial, or military explosives. To operate, a residue is collected by rubbing a special wipe on an object or a person. The sample is heated until it is becomes gaseous. Then, it is transferred into a separation chamber in which individual compounds are separated using gas chromatography. All the compounds containing nitro-groups are selected and identified using mass spectrometry. Many high explosives contain one or more nitro-groups [that is, nitrogen (N), nitrate (NO3), nitrite (NO2)], which is why the EGIS system focuses upon these. EGIS can positively identify a mass of these explosives as small as one trillionth of a gram. Hence, it is a highly effective detection method. The system’s primary disadvantage is that analysis requires quite a long time.

Ion Mobility Spectrometry (IMS): IMS technology can detect small quantities of explosives accurately and quickly. This technique uses jets of air to blow molecules from skin, clothes, or objects such as luggage. The molecules become electrically charged during this process and are drawn into a detector that identifies the explosives (or drugs) according to their distinct electrical properties. The error rate of the IMS is said to be less than 0.1%. Devices that use IMS technology come in various forms such as hand-held units, tabletop models, or walk-through systems that resemble the metal detectors used in airports.

In 1988, the Lockerbie air disaster became the deadliest terrorist attack on U.S. civilians until the 9-11 World Trade Center tragedy occurred in 2001.

Pan Am flight 103 was a large Boeing 747 that flew daily between London's Heathrow International Airport and New York's John F. Kennedy International Airport. Just a few days before Christmas 1988, an explosive device was detonated on the airplane, which caused the aircraft to explode in mid-air. The plane’s fuselage and the bodies of the 270 crew and passengers were scattered across an area near Lockerbie, Scotland. Eleven inhabitants of the small town were also killed.

The Explosion: The fuselage of the aircraft was reconstructed by air accident investigators. It revealed a 45 cm hole in the front cargo hold of the airplane. Examination of fragments from front cargo hold showed an area of blackening, pitting, and severe damage. Investigators conducted a series of test explosions to confirm the precise location and quantity of explosive used.

Investigators concluded that the nose separated from the main section of the aircraft within three seconds of the explosion. Because the explosion happened so quickly, the crew were unable to place a distress call. Winds of 190 kilometres per hour scattered victims and plane debris over approximately 2189 square kilometres.

The nose of the airplane, which was found in Lockerbie, contained all the bodies of the flight crew and several first class passengers. Examination of the cockpit showed that no crew member was wearing an oxygen mask. This is further evidence that indicating there was no time to begin any emergency procedures.

As it fell from the sky, the main section of the plane broke into smaller pieces. A large section attached to the wings landed in the middle of a residential area of Lockerbie. Aviation fuel in the tanks in the wings ignited to cause a huge fire destroying several houses. The fire was so intense that nothing remained of the left wing and the only way investigators were able to determine where the plane’s wings had landed was by finding a large number of large screws used only in the wings in the fire debris.

The initial crash site was investigated by local police. However, the military also helped by providing helicopter surveys and satellite imaging. More than 10 000 pieces of evidence was found, tagged, and entered into a computer tracking system.

Cause of the Explosion

Forensic investigators determined that about 450 grams of a plastic explosive called Semtex hidden inside an unaccompanied piece of luggage was responsible for the explosion. Fragments of a Samsonite suitcase believed to have contained the explosive device were recovered, as were pieces of a circuit board from a radio cassette player. The time-delay explosive device was concealed inside the radio cassette player that was hidden in the suitcase along with some baby clothes.

Semtex is a general-purpose plastic explosive developed in the Czech Republic in the 1960s. Semtex was originally designed for commercial blasting and demolition; however, it became popular with terrorists because it cannot be detected by metal detectors and it is easy to obtain. Prior to the 1990s, Semtex could not be detected by X-ray machines. Semtex is considered very effective for attacks on airplanes because only a small amount is needed to destroy a large commercial passenger airplane. Semtex has been used in attacks by Middle Eastern Islamic militant groups, the Irish Republican Army (IRA), and the Irish National Liberation Army. Prior to 2002, Semtex was widely exported. The country receiving the most of this explosive was Libya with over 700 tonnes being imported between 1975 and 1981.

Because Semtex has been associated with terrorist attacks, production and export of Semtex today has been restricted to about 10 tonnes per year only. In addition, the chemical compound, ethylene glycol dinitrate, which is easily identified by explosive detection devices, is now added to Semtex.

The Warning: A few weeks prior to the explosion, a man with an Arabic accent phoned the U.S. Embassy in Finland and warned them that a Pan Am flight from Frankfurt to the United States would be blown up within the next two weeks by someone associated with the Abu Nidal Organization, a Palestinian terrorist group. The caller said a woman passenger would unknowingly carry the bomb aboard. The threat was taken seriously, and bulletins were sent to dozens of embassies and American airline companies. Unfortunately, despite the warnings the bomb slipped on board Pan Am flight 103.

The Bombers: After a three-year joint investigation by local police agencies in Scotland and the FBI, indictments for murder were issued for two men from Libya. Both men worked for Libyan Arab Airlines (LAA). One suspect was the head of security while the other was a station manager for LAA. Extradition of the two culprits from Libya to Scotland where they were tried took more than eight years. The extradition involved United Nations sanctions against Libya and direct negotiations with the Libyan leader Colonel Muammar al-Gaddafi.

In 2001, one of the culprits was convicted of murder and sentenced to 27 years in prison by a panel of three Scottish judges. The other suspect was acquitted.

Why did investigators reconstruct parts of the airplane involved in this explosion?
Ans.  The airplane was reconstructed to determine the site or origin of the bomb.

Where was the site of origin of the explosion? How was this determined?
Ans. Investigators determined this by examining fragments from the front cargo hold, which showed an area of blackening, pitting, and severe damage.

The explosion originated in the front cargo hold.

What type of bomb was used—high or low?
Ans.  A high explosive device was used.

Old Fire

In October 2003, an arsonist in the San Bernardino Mountains of California started a blaze known as the Old Fire. The fire burned 369.4 km², destroyed 993 homes, forced nearly 80 000 people from their homes, and caused six deaths and $42 million of damage.

Esperanza Fire

In October 2006, the Esperanza Fire occurred in the Banning area of California. The cost to extinguish the fire was more than $8 million. It burned more than 160 km², destroyed 34 houses and 20 buildings, and killed five firefighters protecting a vacant, partially built home that eventually burned. The firefighters were overwhelmed when the winds shifted and blew a wall of flames towards them. Three of the firefighters died at the scene; the two others were found alive with severe injuries but died later in hospital.

The Arrest

Shortly after the deadly Esperanza Fire was determined to have been caused by arson, a $600 000 reward was offered for information leading to the arrest and conviction of the arsonist(s). The reward worked. In early November 2006, law enforcement officials arrested and charged Raymond Lee Oyler, a 36-year-old auto mechanic, with setting the Old Fire, the Esperanza Fire, and 20 other wildfires in the area. In addition to arson, Oyler was charged with five counts of first-degree murder. Fifty-five arson fires were reported from May 2006 until the time of Oyler's arrest. No arson fires occurred in the area after his arrest.

Oyler denied all the charges, telling investigators that, on the night of the Esperanza Fire, he was at a casino, and then he stopped at a gas station before driving to the wildfire to watch it.

The Evidence

Finding evidence in cases of arson is difficult because the fires usually destroy the evidence. However, the forensic arson experts in the Old Fire and Esperanza Fire investigations were meticulous. Consequently, they found several pieces of evidence to support their case.

Serial arsonists are often predictable because they tend to use the same type of incendiary device for each fire. All but one of the fires Oyler was charged with were started with nearly identical homemade incendiary devices consisting of five to seven paper or wood matches attached around a Marlboro cigarette with duct tape or a rubber band. When the cigarette was lit, it burned slowly until it reached the matches, ignited them, and started a brush fire. Each device allowed a time delay of more than 10 minutes, during which Oyler would leave the scene and create an alibi. On cigarette butts in two of the incendiary devices found, investigators discovered DNA evidence that matched Oyler.

Investigators also had video footage from secret cameras atop utility poles that filmed Oyler's car leaving the scene of one of the fires. Ironically, surveillance videos from the casino and the gas station that Oyler said he was at during the Esperanza Fire showed he was not at either location during these times.

Oyler’s cousin and his girlfriend provided evidence that incriminated Oyler. Both acknowledged that Oyler owned a book called Anarchist Cookbook that discussed how to make devices to start fires. They acknowledged that he had boasted about lighting fires. Four days before the Esperanza Fire, Oyler said he wanted to set some fires near an animal facility where his pit bull was being held after it had bit a woman.

The Trial

At the trial, Oyler's sister testified that he was at home when the Esperanza Fire began. Despite this testimony, in 2009, a jury convicted Raymond Lee Oyler of five counts of first-degree murder, nineteen counts of arson, and sixteen counts of possessing incendiary devices. The court sentenced Oyler to death despite the pleas of Oyler's lawyer that he should receive a reduced sentence of life in prison without the possibility of parole.

Criticism

After the tragic death of five firefighters in the Esperanza Fire, many criticized the decision to send a firefighting crew to protect a single vacant, partially built house. Some suggested that firefighters should not be sent to protect vacant houses or isolated individual homes. If this suggestion had been followed, five firefighters would very likely be alive today.

The Oklahoma City bombing was a terrorist attack occurring in April 1995. The Alfred P. Murrah Federal Building, a U.S. government highrise in downtown Oklahoma City, was bombed, the explosion killing 168 people, including children, and injuring over 800 more.

Planning and Preparation

Timothy McVeigh rented a truck in Kansas and drove it to Oklahoma City with Terry Nichols, his accomplice. When they arrived in Oklahoma City, they rented a car and parked it a few blocks from the Alfred P. Murrah Federal Building. They removed the license plate from the car and left it. This car would become their getaway vehicle. McVeigh and Nichols then returned to Kansas in their rented truck for two days. They spent two days creating a time-delayed explosive device that they put in the rented truck that they packed with explosives. After finishing the truck-bomb, the two men separated; Nichols returned to his home in Kansas, and McVeigh drove the truck to Oklahoma City.

The Explosive Device

Timothy McVeigh and Terry Nichols fashioned their explosive device from large amounts of several chemical compounds, most of which they stole. The chemicals were mixed using plastic buckets and a bathroom scale. They used more than a hundred 22 kg bags of ammonium nitrate, several 208-litre drums of nitromethane, several crates of explosive Tovex sausage, and numerous bags of ANFO (ammonium nitrate-fuel oil).

After the bomb was completed, a fuse was time-delayed and made to detonate using the truck’s ignition. The determined bombers included extra explosives near the driver's seat to be ignited by McVeigh’s handgun if the main fuse failed.

The Explosion

About 9 a.m. April 19, 1995, Timothy McVeigh parked the truck in a drop-off zone on the north side of the Alfred P. Murrah Federal Building. This drop-off zone was directly under a children’s day-care center. McVeigh then triggered the time-delayed detonator, locked the vehicle, and walked to his getaway car parked a few blocks away.

The explosion destroyed one-third of the entire building and created a 2.4-metre crater with a diameter of 9 metres. The blast destroyed or damaged 324 buildings in a sixteen-block radius, destroyed 86 cars, and shattered windows in 258 neighbouring buildings. The destruction of the Alfred P. Murrah Federal Building left several hundred people homeless and shut many businesses in downtown Oklahoma City.

The Victims

The bombing claimed 168 lives and injured more than 800 people. Of the dead, 160 were from inside the Alfred P. Murrah Federal Building, six were from nearby buildings, one woman was across the street in a parking lot, and one rescue worker was struck in the head by debris. The victims ranged in age from three months to 73 years. Tragically, three victims were pregnant women and 19 were children. Family members identified the bodies at a temporary morgue on site. Medical experts determined the identities using X-rays, dental examinations, fingerprints, blood tests, and DNA analysis. The explosion injured 853 people, the majority having various abrasions, severe burns, and fractures.

The Rescue Effort

Just minutes after the explosion, ambulances, police, and firefighters arrived. They were soon assisted by the Civil Air Patrol, the American Red Cross, and citizens who had witnessed the blast. More than four hundred members of the Oklahoma National Guard arrived within an hour of the explosion to provide security. This immediate action led to the rescue of fifty injured people within the first hour.

About 1.5 hours after the explosion, rescue workers found what appeared to be a second bomb. Many rescue workers initially refused to leave, but police ordered a mandatory evacuation of a four-block area around the site. This evacuation was cancelled when the device was determined to be only an explosive simulation device used in training explosive detection dogs.

In the days that followed, more than 12 000 people helped in the massive rescue and clean-up operation. Twenty-four police service tracking dogs searched for survivors and bodies in the debris. For ten days following the attack, 100 to 350 tons of rubble were removed from the site each day. The rescue and clean-up operation was completed in 35 days and the remains of the Alfred P. Murrah Federal Building were demolished.

The Arrests

Just 90 minutes after the explosion, an Oklahoma Highway Patrol officer pulled over 27-year-old Timothy McVeigh as he travelled out of Oklahoma City. He was arrested for driving without a license plate and carrying a concealed handgun. Later that day, McVeigh was linked to the bombing when investigators found the serial number from the axle of the destroyed rental truck. McVeigh was a 27-year-old decorated U.S. Army veteran of the Persian Gulf War, and he was sympathizer of an anti-government militia movement.

Federal agents then searched for Terry Nichols. Two days after the bombing, Nichols learned that investigators were looking for him and he turned himself in. McVeigh and Nichols’ motive was to avenge the U.S. government’s raid of the Branch Davidian sect in Waco, Texas, in which 80 people died.

A third suspect named Michael Fortier was also eventually arrested. Fortier was a friend of Timothy McVeigh and Terry Nichols. He had an indirect role in the bombing by helping steal some of the bomb supplies and accompanying McVeigh on a previous visit to the Alfred P. Murrah Federal Building to plan the bombing.

The Criminal Trials

At that time, the Oklahoma City Bombing was the largest criminal case in U.S. history. Nearly 28 000 interviews were conducted and evidence weighed more than 3 tonnes. The massive investigation led to separate trials and convictions for Timothy McVeigh and Terry Nichols.

In June 1997, a jury found Timothy McVeigh guilty of eleven counts of murder and conspiracy. McVeigh was sentenced to death and was executed by lethal injection in June 2001. The execution was televised and watched by relatives of the victims.

Terry Nichols was tried in federal court in 1997 and found guilty of conspiring to build a weapon of mass destruction and of eight counts of involuntary manslaughter. He was sentenced to life without parole. Then in May 2004, he was found guilty of 161 counts of first-degree murder. The jury deadlocked regarding the issue of sentencing him to death, so the presiding judge gave Nichols a sentence of 161 consecutive life terms without the possibility of parole.

Michael Fortier agreed to testify against McVeigh and Nichols in exchange for a modest sentence and immunity for his wife. As a result, Fortier was given only 12 years in prison and a $200 000 fine for failing to warn authorities about the attack. On January 20, 2006, after serving 85% of his prison term, Fortier was released for good behaviour. Michael Fortier and his wife were placed in the Witness Protection Program and given new identities.

An Aerial Photograph of the Oklahoma City Bombing Site

- Image Source: courtesy Wikipedia.org