CFL Tool Mark Analysis 2 — Questions and Answers
Question 1: Which microscopy technique is most commonly used to compare striated tool marks in forensic locksmith casework?
- Scanning electron microscopy
- Comparison microscopy (Correct answer)
- Polarized light microscopy
- Atomic force microscopy
Correct answer: Comparison microscopy
Comparison microscopy allows two specimens to be viewed simultaneously side-by-side, making it the standard tool for striation comparison.
Question 2: A 'negative impression' tool mark is best described as:
- A mark made by a blunt instrument
- A three-dimensional impression where the tool shape is transferred into the substrate (Correct answer)
- A photographic reversal of a tool mark
- A mark with no discernible striae
Correct answer: A three-dimensional impression where the tool shape is transferred into the substrate
Negative impression marks are three-dimensional indentations where the contours of the tool are pressed into the softer substrate.
Question 3: In tool mark analysis, 'individual characteristics' are defined as:
- Features shared by all tools of the same manufacturer
- Random imperfections acquired during manufacture or use that distinguish one tool from all others (Correct answer)
- Markings stamped on tools for identification
- Class features that narrow the tool to a specific type
Correct answer: Random imperfections acquired during manufacture or use that distinguish one tool from all others
Individual characteristics are random, unique features such as nicks and scratches that allow a specific tool to be identified to the exclusion of all others.
Question 4: When examining cut copper wire in a forensic context, the examiner should focus primarily on which surface?
- The outer insulation surface
- The cross-sectional cut face of the wire strands (Correct answer)
- The oxidized exterior of the wire
- The solder joints at wire terminations
Correct answer: The cross-sectional cut face of the wire strands
The cross-sectional cut face of wire strands contains the striae and class characteristics left by the cutting tool's blade.
Question 5: Which of the following best explains why test marks should be made on the same type of substrate as the evidence?
- To save time during laboratory analysis
- Because substrate hardness affects the nature and depth of tool marks produced (Correct answer)
- To ensure the tool is not damaged during testing
- Because different substrates require different microscopes
Correct answer: Because substrate hardness affects the nature and depth of tool marks produced
Substrate hardness and material properties directly influence mark morphology, so test marks must be made on matching material for valid comparison.
Question 6: A forensic locksmith finds drag marks on a door frame consistent with a pry bar. To establish a link to a suspect's tool, the examiner should:
- Photograph the marks and estimate tool width only
- Make test marks with the suspect tool on similar substrate and compare striations under magnification (Correct answer)
- Polish the suspect tool and check for paint transfer
- Request a DNA swab of the tool marks
Correct answer: Make test marks with the suspect tool on similar substrate and compare striations under magnification
Test marks created with the suspect tool on matching substrate are compared microscopically to evidence marks to identify or exclude the tool.
Question 7: What is the significance of 'consecutively manufactured tools' in tool mark analysis research?
- They always produce identical marks and cannot be differentiated
- They demonstrate that even tools made sequentially on the same machine acquire unique individual characteristics (Correct answer)
- They are used only in controlled laboratory settings
- They share all individual characteristics due to the same die
Correct answer: They demonstrate that even tools made sequentially on the same machine acquire unique individual characteristics
Studies on consecutively manufactured tools confirm that random surface variations arise even in tools produced back-to-back, supporting individualization.
CFL Tool Mark Analysis 2
Which microscopy technique is most commonly used to compare striated tool marks in forensic locksmith casework?