ACTAR Evidence Documentation & Interpretation 5 — Questions and Answers
Question 1: A 'furrow' in soil or grass at a crash scene is most useful for establishing:
- The vehicle's pre-crash speed on the roadway
- The vehicle's direction of travel and trajectory after leaving the roadway (Correct answer)
- The force of impact between two vehicles
- The driver's reaction time before the crash
Correct answer: The vehicle's direction of travel and trajectory after leaving the roadway
Furrows left in soil or vegetation by a vehicle document its post-roadway trajectory, heading, and path as it traveled across terrain.
Question 2: For a crash reconstruction report to be admissible under Daubert standards, the methodology used must be:
- Based solely on the investigator's field experience
- Tested, peer-reviewed, have known error rates, and be generally accepted in the scientific community (Correct answer)
- Approved by the local law enforcement agency
- Derived only from published NHTSA standards
Correct answer: Tested, peer-reviewed, have known error rates, and be generally accepted in the scientific community
Daubert requires scientific testimony to be based on methodology that has been tested, peer-reviewed, has known error rates, and is generally accepted within the relevant scientific community.
Question 3: What is the correct procedure when an investigator arrives at a crash scene and finds that critical tire marks have already been partially obscured by rain?
- Abandon measurement of the marks as they are no longer reliable
- Document the remaining visible portions with photographs and measurements, noting the degradation (Correct answer)
- Estimate the original mark length based on vehicle type and assumed speed
- Wait for the rain to stop completely before any documentation
Correct answer: Document the remaining visible portions with photographs and measurements, noting the degradation
Remaining visible evidence should be documented immediately with photographs and measurements, with clear notation of the degradation, as partial evidence is better than no evidence.
Question 4: Which vehicle damage feature most directly indicates the height of a striking or struck object?
- The width of the damage zone
- The vertical location of the principal contact area (PCA) on the vehicle (Correct answer)
- The length of the crumple zone deformation
- The horizontal extent of paint transfer
Correct answer: The vertical location of the principal contact area (PCA) on the vehicle
The vertical position of the principal contact area on the vehicle's structure directly indicates the height above ground of the object or vehicle that caused the damage.
Question 5: When using photogrammetry to extract measurements from crash scene photographs, which condition is MOST critical for accurate results?
- All photographs must be taken with the same camera model
- Known control points with precise coordinates must be visible in the photographs (Correct answer)
- The photographs must be taken in RAW format only
- Only aerial photographs can be used for photogrammetry
Correct answer: Known control points with precise coordinates must be visible in the photographs
Photogrammetry requires identifiable control points with known 3D coordinates present in the images to scale and orient the photogrammetric model accurately.
Question 6: In crash reconstruction, 'paint transfer evidence' is primarily used to:
- Determine vehicle speed at impact
- Match vehicles involved and establish contact points and geometry (Correct answer)
- Calculate the coefficient of restitution
- Identify the age of the vehicles involved
Correct answer: Match vehicles involved and establish contact points and geometry
Paint transfer analysis matches transferred paint to source vehicles, confirms contact, and helps establish the geometry and orientation of the vehicles at the moment of impact.
Question 7: A witness describes a vehicle as 'fishtailing' before a crash. In evidence documentation, which physical evidence at the scene would corroborate this account?
- Long, straight parallel skid marks from all four wheels
- Curved, striated yaw marks indicating rear-wheel sideslip (Correct answer)
- A single straight tire mark from the front wheels only
- No tire marks, because fishtailing leaves no evidence
Correct answer: Curved, striated yaw marks indicating rear-wheel sideslip
Fishtailing involves the rear of the vehicle sliding sideways (yaw), which produces curved, striated yaw marks on the pavement surface that corroborate witness accounts.
ACTAR Evidence Documentation & Interpretation 5
A 'furrow' in soil or grass at a crash scene is most useful for establishing: