BSFS Bachelor of Science in Forensic Science 5 — Questions and Answers
Question 1: Which statistical concept is central to interpreting DNA evidence and expressing the rarity of a DNA profile?
- Standard deviation of allele sizes
- Random match probability calculated from population databases (Correct answer)
- P-value from a t-test comparing samples
- Bayes theorem applied to fingerprint minutiae
Correct answer: Random match probability calculated from population databases
Random match probability estimates how likely it is that a randomly chosen unrelated person from the population would share the same DNA profile, typically expressed as 1 in billions or trillions.
Question 2: What is the role of a 'known standard' in forensic firearms examination?
- A reference weapon used to certify examiner credentials
- Test-fired ammunition from the suspect weapon used to compare toolmarks with evidence cartridges (Correct answer)
- A federal database of registered firearms
- A calibration tool for measuring bullet caliber
Correct answer: Test-fired ammunition from the suspect weapon used to compare toolmarks with evidence cartridges
A known standard consists of cartridge cases and bullets test-fired from the suspect firearm, providing toolmark samples for direct microscopic comparison with evidence recovered at the scene.
Question 3: Which type of impression evidence can be collected from a soft surface like mud or snow at a crime scene?
- Two-dimensional lift using electrostatic lifting device
- Three-dimensional cast using dental stone or sulfur casting compound (Correct answer)
- Fluorescent powder dusting
- Cyanoacrylate fuming
Correct answer: Three-dimensional cast using dental stone or sulfur casting compound
Three-dimensional impressions in soft surfaces like mud, snow, or soil are cast with dental stone or similar casting compound to create a permanent physical replica.
Question 4: In forensic chemistry, what distinguishes a 'confirmatory test' from a 'presumptive test'?
- Confirmatory tests are faster; presumptive tests are more accurate
- Presumptive tests indicate possible presence of a substance; confirmatory tests provide definitive identification (Correct answer)
- Confirmatory tests use only reagents; presumptive tests use instruments
- There is no practical difference in forensic practice
Correct answer: Presumptive tests indicate possible presence of a substance; confirmatory tests provide definitive identification
Presumptive tests are rapid screening methods that suggest the possible presence of a substance, while confirmatory tests use methods like GC-MS to provide scientifically definitive identification.
Question 5: What is 'trace evidence' in the context of forensic science?
- Digital records left on a computer
- Small, often microscopic physical material transferred during criminal activity (Correct answer)
- Witness accounts of a crime
- Financial records linking a suspect to a crime
Correct answer: Small, often microscopic physical material transferred during criminal activity
Trace evidence refers to small physical materials such as hairs, fibers, glass fragments, soil, and pollen that are transferred during the commission of a crime.
Question 6: Which method is used to detect gunshot residue (GSR) on a suspect's hands?
- Infrared spectroscopy on hand swabs
- Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) (Correct answer)
- Immunoassay test strips
- High-performance liquid chromatography (HPLC)
Correct answer: Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX)
SEM-EDX is the standard method for GSR analysis because it detects and characterizes the unique tri-elemental particles (lead, barium, antimony) from primer discharge.
Question 7: What does the term 'forensic taphonomy' study?
- The analysis of handwriting in legal documents
- The processes of decomposition and environmental factors affecting human remains after death (Correct answer)
- The chemical composition of soil samples at crime scenes
- The psychological profiling of criminal behavior
Correct answer: The processes of decomposition and environmental factors affecting human remains after death
Forensic taphonomy examines postmortem changes to human remains caused by biological, chemical, and physical environmental processes to assist in estimating time of death and understanding body disposition.
BSFS Bachelor of Science in Forensic Science 5
Which statistical concept is central to interpreting DNA evidence and expressing the rarity of a DNA profile?