Question 1: What is the primary characteristic that allows forensic examiners to match a tool mark to a specific tool?
- A. The general shape of the mark
- B. Microscopic striations and imperfections
- C. The color of the mark
- D. The size of the mark
Answer
Answer: B. Microscopic striations and imperfections
Explanation: The unique microscopic striations and imperfections left by a tool’s wear patterns serve as its “fingerprint.” These minute characteristics are created during manufacturing and through use, allowing for positive identification even when multiple tools of the same make and model exist.
Question 2: Which of the following tools would most likely leave compression marks rather than striated marks?
- A. A screwdriver used to pry open a window
- B. Bolt cutters used to cut a padlock
- C. A chisel used to scrape wood
- D. Pliers used to twist wire
Answer
Answer: B. Bolt cutters used to cut a padlock
Explanation: Bolt cutters typically leave compression (indentation) marks rather than striated marks because they work by applying crushing force perpendicular to the surface. The other tools listed would primarily create striated marks through parallel motion against a surface.
Question 3: What is the most critical step in the forensic analysis of tool marks at a crime scene?
- A. Photographing the marks with scale references
- B. Making test marks with suspected tools
- C> Casting three-dimensional impressions
- D. Measuring the depth of the marks
Answer
Answer: A. Photographing the marks with scale references
Explanation: Proper documentation through photography with scale references is the most critical first step, as it preserves the original evidence before any potentially destructive analysis. This creates a permanent record that can be used even if the original mark is damaged during subsequent examination.
Question 4: Which analytical technique has become increasingly important for tool mark analysis due to its ability to create 3D digital comparisons?
- A. Scanning electron microscopy (SEM)
- B. Confocal microscopy
- C. Atomic force microscopy (AFM)
- D. Laser scanning profilometry
Answer
Answer: D. Laser scanning profilometry
Explanation: Laser scanning profilometry has revolutionized tool mark analysis by creating high-resolution 3D digital models of marks that can be compared quantitatively. This technology allows for objective comparisons and eliminates some of the subjectivity of traditional microscopic comparisons.
Question 5: What type of tool mark would be most likely found on the surface of a lock that has been picked?
- A> Shear marks
- B. Impression marks
- C. Scrape marks
- D. Pin tumbler impressions
Answer
Answer: C. Scrape marks
Explanation: Lock picking typically leaves fine scrape marks on the internal components (especially pin tumblers) as the picking tools manipulate the mechanism. These striated marks can sometimes be matched to specific picking tools.
Question 6: When analyzing saw marks on bone or wood, what feature can indicate whether the saw was a push or pull type?
- A. The angle of the striations
- B. The presence of exit chipping
- C. The curvature of the mark walls
- D. The pattern of tooth impressions
Answer
Answer: C. The curvature of the mark walls
Explanation: The curvature of the mark walls (known as “kerf wall morphology”) differs between push and pull strokes due to the direction of force application and tooth design. This can help determine whether the saw was Western-style (push) or Asian-style (pull) in design.
Question 7: What is the primary limitation of tool mark analysis compared to fingerprint analysis?
- A. Tools cannot be uniquely identified
- B. Tool marks degrade faster than fingerprints
- C. Tool mark analysis is more subjective
- D. Tools cannot be chemically enhanced
Answer
Answer: C. Tool mark analysis is more subjective
Explanation: Unlike fingerprint analysis which has established minimum point standards for identification, tool mark analysis relies more on the examiner’s experience and judgment. The lack of universally accepted quantitative standards makes it more subjective, though emerging 3D analysis technologies are addressing this limitation.
Question 8: Which factor is most likely to prevent a positive identification between a tool and mark?
- A. The tool was cleaned after use
- B. The mark was made on a soft material
- C. The tool was used at an angle
- D. The mark contains debris
Answer
Answer: B. The mark was made on a soft material
Explanation: Soft materials like lead or plastic often don’t retain the fine microscopic characteristics needed for positive identification. They may record the general shape but lack the detailed striations that would allow for conclusive matching.
Question 9: What type of tool mark evidence would be most valuable for determining the sequence of events in a burglary?
- A. Overlapping tool marks
- B. Paint transfers within marks
- C. Depth measurements
- D. Rust deposits in marks
Answer
Answer: A. Overlapping tool marks
Explanation: Overlapping tool marks can reveal the sequence in which different tools were used or when the same tool was applied multiple times. This temporal information can help reconstruct the burglar’s actions and methods.
Question 10: When test marks are made with a suspected tool for comparison purposes, what is the most critical factor?
- A. Using the same angle and pressure as the original mark
- B. Making marks on identical material
- C. Creating marks of the same size
- D. Performing tests in the same environment
Answer
Answer: A. Using the same angle and pressure as the original mark
Explanation: Reproducing the same angle and pressure is critical because tool marks change significantly with different application parameters. While material similarity helps, the mechanics of tool mark creation are most dependent on how the tool was applied.