BSFS General 2 — Questions and Answers
Question 1: Which type of evidence is considered most reliable in establishing a suspect's presence at a crime scene?
- Eyewitness testimony
- DNA evidence (Correct answer)
- Circumstantial evidence
- Character witness statements
Correct answer: DNA evidence
DNA evidence is highly reliable because it can uniquely identify an individual with extremely high statistical certainty.
Question 2: What is 'Locard's Exchange Principle' in forensic science?
- Every criminal leaves a signature at crime scenes
- Every contact leaves a trace between two surfaces (Correct answer)
- Physical evidence must be photographed before collection
- Witnesses exchange information with investigators
Correct answer: Every contact leaves a trace between two surfaces
Locard's Exchange Principle states that whenever two objects come into contact, material is transferred between them.
Question 3: In forensic toxicology, what does a 'chain of custody' document ensure?
- The suspect was read their Miranda rights
- The integrity and accountability of a sample from collection to court (Correct answer)
- Laboratory equipment is properly calibrated
- The toxicologist has proper credentials
Correct answer: The integrity and accountability of a sample from collection to court
Chain of custody documentation tracks every person who handled a sample, ensuring its integrity is unbroken and legally defensible.
Question 4: What is the role of a 'control sample' in forensic laboratory analysis?
- To document the crime scene layout
- To serve as a known standard for comparison and quality assurance (Correct answer)
- To store excess evidence securely
- To provide a second opinion on findings
Correct answer: To serve as a known standard for comparison and quality assurance
A control sample with known properties confirms that analytical procedures are working correctly and results are valid.
Question 5: Which federal law governs the admissibility of scientific expert testimony in US federal courts?
- The Innocence Protection Act
- The Federal Rules of Evidence (Daubert standard) (Correct answer)
- The Brady Act
- The Uniform Code of Military Justice
Correct answer: The Federal Rules of Evidence (Daubert standard)
The Daubert standard, derived from Daubert v. Merrell Dow Pharmaceuticals and codified in the Federal Rules of Evidence, requires judges to assess the scientific validity of expert testimony.
Question 6: What does the term 'postmortem interval' (PMI) refer to in forensic pathology?
- The time between arrest and autopsy
- The elapsed time since a person died (Correct answer)
- The duration of a coroner's investigation
- The interval between cause and manner of death
Correct answer: The elapsed time since a person died
Postmortem interval is the estimated time that has elapsed since death, determined using biological and environmental indicators.
Question 7: Which analytical technique is most commonly used in forensic laboratories to separate and identify components of a mixture?
- Spectrophotometry
- Gas chromatography-mass spectrometry (GC-MS) (Correct answer)
- Atomic absorption spectroscopy
- X-ray diffraction
Correct answer: Gas chromatography-mass spectrometry (GC-MS)
GC-MS is considered the gold standard in forensic chemistry for separating mixture components and identifying them by their mass spectra.
BSFS General 2
Which type of evidence is considered most reliable in establishing a suspect's presence at a crime scene?