FBI Forensic Science & Analysis 3 — Questions and Answers
Question 1: A forensic examiner determines a bullet's caliber by measuring its diameter. A bullet measuring approximately 9mm in diameter is consistent with which of the following cartridges?
- .38 Special
- 9mm Luger (9x19mm) (Correct answer)
- .40 S&W
- .357 Magnum
Correct answer: 9mm Luger (9x19mm)
The 9mm Luger (9x19mm Parabellum) uses a bullet that is approximately 9mm (0.355 inches) in diameter, making it the direct match.
Question 2: When documenting a shooting scene, agents use the term 'entrance wound characteristic' to describe a feature. Which feature is most reliably associated with a contact gunshot entrance wound?
- Muzzle contusion ring (stellate tearing) (Correct answer)
- Stippling (tattooing) pattern around the wound
- Lead wipe ring
- Grease collar
Correct answer: Muzzle contusion ring (stellate tearing)
Contact wounds show stellate (star-shaped) tearing caused by hot propellant gases entering tissue and expanding rapidly before exiting, creating a characteristic pattern.
Question 3: In a questioned document examination, an examiner is asked to determine if two signatures were written by the same person. Which class of handwriting characteristic is examined FIRST?
- Individual characteristics unique to one writer
- Line quality and pen pressure
- Class characteristics such as letter forms and proportions (Correct answer)
- Habitual characteristics like tremor patterns
Correct answer: Class characteristics such as letter forms and proportions
Class characteristics, including general letter forms, spacing, and proportions, are assessed first to determine if signatures belong to the same broad writing system before examining individual characteristics.
Question 4: An FBI lab receives a soil sample from a suspect's boots. Which forensic discipline would analyze mineral composition and pollen content to associate the soil with a specific geographic location?
- Serology
- Forensic geology and palynology (Correct answer)
- Toxicology
- Digital forensics
Correct answer: Forensic geology and palynology
Forensic geology analyzes mineral composition while palynology examines pollen and spores, together providing geographic location evidence through soil comparison.
Question 5: Which type of fingerprint pattern is the most common in the general population, accounting for approximately 65% of all fingerprints?
- Arch
- Loop (Correct answer)
- Whorl
- Tented arch
Correct answer: Loop
Loop patterns are the most common fingerprint pattern type, found in approximately 60-65% of the population, with whorls second at about 30-35%.
Question 6: When analyzing trace evidence from a hit-and-run vehicle, glass fragments are recovered from the victim's clothing. Which optical property is MOST useful for comparing glass fragments?
- Surface texture
- Refractive index (Correct answer)
- Color under UV light
- Fragment size distribution
Correct answer: Refractive index
Refractive index is the most discriminating optical property for glass comparison because it is highly specific to each glass batch and can be measured precisely using oil immersion techniques.
Question 7: An agent collects fibers from a kidnapping victim's clothing. The forensic examiner uses polarized light microscopy to analyze the fibers. What fiber characteristic is best determined by this technique?
- Fiber length distribution
- Birefringence and fiber type classification (Correct answer)
- Dye absorption spectrum
- Tensile strength
Correct answer: Birefringence and fiber type classification
Polarized light microscopy measures birefringence (the difference in refractive indices), which helps classify fiber type such as distinguishing natural from synthetic fibers.
FBI Forensic Science & Analysis 3
A forensic examiner determines a bullet's caliber by measuring its diameter.
A bullet measuring approximately 9mm in diameter is consistent with which of the following cartridges?