Vehicle fire, arson and explosion investigation
This domain tests whether you can separate accidental vehicle fires from intentional fires and explosions, and whether you can investigate both without jumping to conclusions. The exam emphasizes evidence-based indicators, explosion dynamics, and scene documentation.
Core rules
- Vehicle fires are frequently accidental. Arson is a conclusion supported by evidence, not by the amount of damage or the presence of gasoline.
- Evaluate potential intentional indicators together: multiple independent origins, accelerant pour patterns, ignition devices, removed valuables, defeated safety systems, and inconsistent owner statements.
- Treat explosion scenes as physical-damage problems: locate the seat, map overpressure and fragmentation, distinguish low-order from high-order damage, and consider fuel-air, confined-space, and vessel failures.
- For vehicles, consider fuel tanks, CNG/LPG cylinders, hydrogen systems, batteries, and aftermarket modifications as explosion energy sources, as well as placed devices.
- Document VIN, registration, ownership, insurance, financial motive, keys, prior damage, and recent repairs; these facts support or weaken hypotheses.
Worked example
A burned SUV has separate burn areas in the cargo area and under the rear seat. A bystander reports gasoline odor, and the owner’s laptop and tools are missing. Reasoning: separate origins and accelerant odor raise an intentional-fire hypothesis, but odor is not identification, and missing property has innocent explanations. The investigator should sample both areas with proper containers and blanks, compare burn patterns with fuel-system and electrical damage, and interview the owner and first responders. If laboratory results confirm ignitable-liquid residue and other accidental sources are excluded, an intentional cause is better supported; otherwise the cause may remain undetermined.
Traps that cost marks
- Equating gasoline odor with accelerant proof; laboratory confirmation is needed.
- Assuming an explosion means a bomb; fuel-air and vessel failures are common.
- Labeling a fire intentional because the vehicle was old or heavily damaged.
- Failing to document negative findings that rule out accidental sources.