CFL Tool Mark Analysis 3 — Questions and Answers
Question 1: In the context of forced entry, 'compression marks' on a lock face are most indicative of:
- A picking attempt
- Impact or prying force applied perpendicular to the surface (Correct answer)
- Key duplication
- Lubricant contamination
Correct answer: Impact or prying force applied perpendicular to the surface
Compression marks result from direct force pressing into the surface, such as a hammer blow or pry bar tip applied perpendicularly.
Question 2: Which standard provides guidelines for the documentation and reporting of tool mark examinations in the United States?
- ASTM E2369
- SWGTREAD guidelines
- SWGMAT tool mark examination guidelines (Correct answer)
- ISO 17025 calibration standard
Correct answer: SWGMAT tool mark examination guidelines
SWGMAT (Scientific Working Group for Materials Analysis) developed the forensic guidelines specifically for tool mark examination.
Question 3: A dimple or raised burr on the shank of a picked lock pin is most likely caused by:
- Thermal expansion during normal use
- The pick tool applying lateral pressure and scratching the pin surface (Correct answer)
- Corrosion from humidity
- Manufacturing defect in the pin stack
Correct answer: The pick tool applying lateral pressure and scratching the pin surface
During picking, the pick tool contacts and applies lateral pressure to pins, leaving striae or burrs on their surfaces.
Question 4: When photographing tool marks for forensic documentation, oblique lighting is preferred because it:
- Eliminates reflections entirely
- Enhances depth and texture by casting shadows across surface features (Correct answer)
- Provides uniform color rendering
- Reduces exposure time
Correct answer: Enhances depth and texture by casting shadows across surface features
Oblique (raking) light strikes the surface at a low angle, casting shadows that reveal the topography of striae and impressed marks.
Question 5: A forensic locksmith examining a padlock shackle cut with bolt cutters would expect to find:
- Smooth, polished cut surfaces with no striae
- Striated marks on the shear faces corresponding to the blade edges of the cutters (Correct answer)
- Thermal discoloration indicating the shackle was torched
- Only class characteristics with no individual features
Correct answer: Striated marks on the shear faces corresponding to the blade edges of the cutters
Bolt cutters leave striated shear marks on the cut surface that reflect the blade geometry and surface imperfections of the tool.
Question 6: The term 'class characteristics' in tool mark analysis refers to:
- Marks unique to a specific tool
- Features determined by the design and manufacturing process common to a group of tools (Correct answer)
- Characteristics documented only in classroom settings
- Trace evidence transferred from the tool to the substrate
Correct answer: Features determined by the design and manufacturing process common to a group of tools
Class characteristics reflect manufacturing design decisions shared by tools of the same make and model, narrowing identification to a tool type.
Question 7: When a suspect tool cannot be physically tested (e.g., it is missing), an examiner may:
- Issue a definitive identification based on class characteristics alone
- Limit conclusions to 'consistent with' or 'cannot exclude' a tool of that class (Correct answer)
- Use a tool from the same manufacturer as a substitute
- Decline to analyze the evidence at all
Correct answer: Limit conclusions to 'consistent with' or 'cannot exclude' a tool of that class
Without test marks from the actual suspect tool, examiners can only offer conclusions based on class characteristics, not individualization.
CFL Tool Mark Analysis 3
In the context of forced entry, 'compression marks' on a lock face are most indicative of: