Accelerant Detection & Fire Debris Analysis Flashcards
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Read the first 7 Accelerant Detection & Fire Debris Analysis flashcards as text
An investigator suspects accelerant use, but fire debris laboratory analysis returns a negative result. What should be considered as a possible explanation?
Answer: Highly volatile accelerants such as acetone or alcohol may have fully evaporated before samples were collected
Low-boiling point accelerants like acetone, alcohols, and lighter fluid can evaporate completely within hours, leaving no detectable residue even when used in significant quantities.
Why is maintaining a documented chain of custody for fire debris samples critically important?
Answer: It ensures evidence integrity and is required for admissibility in legal proceedings
An unbroken, documented chain of custody demonstrates that evidence has not been tampered with or contaminated, which courts require before admitting forensic evidence.
In GC-MS analysis, what does a 'total ion chromatogram' (TIC) display to the fire debris analyst?
Answer: The total abundance of all detected ions across the entire GC separation time
A TIC plots the sum of all ion abundances detected at each moment during the separation, producing a characteristic 'fingerprint' pattern of the sample's overall composition.
When comparing a questioned fire debris sample to a known ignitable liquid standard in GC-MS analysis, what criterion is applied?
Answer: A consistent pattern of diagnostic compounds is sought rather than requiring a perfect numerical match
Because weathering and matrix effects alter exact ratios, analysts look for consistent diagnostic compound patterns and relative ratios rather than demanding a perfect numerical match.
Which statement best describes the appropriate role of a fire debris laboratory analyst in an arson investigation?
Answer: To identify and classify any ignitable liquid residues present in submitted samples
The analyst's role is strictly limited to scientific identification of ignitable liquid residues; determining whether arson occurred and identifying perpetrators is the fire investigator's responsibility.
ASTM E2958 provides guidance specifically on which aspect of fire debris investigation?
Answer: The significance and interpretation of fire debris analysis data for investigators and courts
ASTM E2958 addresses how to interpret and communicate the significance of laboratory fire debris analysis results, helping investigators and courts understand what findings mean.
What critical precaution should a fire investigator take when collecting soil as a fire debris sample suspected of containing accelerant residues?
Answer: Comparison control samples from unaffected areas of similar soil must also be collected
Control samples from unburned areas of the same soil type allow analysts to identify naturally occurring background petroleum hydrocarbons and distinguish them from accelerant residues.