ACTAR Evidence Documentation & Interpretation 2 — Questions and Answers
Question 1: When photographing tire marks at a crash scene, which lighting technique best reveals surface texture and mark depth?
- Oblique (raking) light from a low angle (Correct answer)
- Overhead flash directly above the mark
- Ambient daylight from directly above
- Infrared photography with no visible light
Correct answer: Oblique (raking) light from a low angle
Oblique or raking light cast at a low angle creates shadows that highlight surface texture and reveal the depth and detail of tire marks.
Question 2: Which document best establishes the chain of custody for a physical evidence item collected at a traffic crash scene?
- The investigator's personal field notes
- A signed evidence log recording each transfer of possession (Correct answer)
- A photograph of the item at the scene
- The final accident reconstruction report
Correct answer: A signed evidence log recording each transfer of possession
A signed evidence log that records every transfer of possession establishes an unbroken chain of custody for physical evidence.
Question 3: In total station surveying of a crash scene, what is the primary advantage over traditional tape-measure methods?
- It requires no line-of-sight between instrument and target
- It simultaneously measures angle and distance to produce precise 3D coordinates (Correct answer)
- It eliminates the need for a reference datum point
- It automatically corrects for magnetic declination
Correct answer: It simultaneously measures angle and distance to produce precise 3D coordinates
A total station simultaneously measures horizontal angle, vertical angle, and slope distance, yielding precise 3D coordinates far faster and more accurately than tape methods.
Question 4: When interpreting a gouge mark in pavement, the deepest portion of the gouge typically indicates what?
- The point of maximum vehicle speed
- The location of principal direction of force (PDOF) contact
- The point of first vehicle contact with the ground (Correct answer)
- The final rest position of a vehicle component
Correct answer: The point of first vehicle contact with the ground
The deepest portion of a gouge mark generally corresponds to the point of first, most forceful contact between a vehicle part and the pavement surface.
Question 5: Aerial drone photography at a crash scene is most valuable for which documentation purpose?
- Capturing close-up detail of fluid stains
- Providing an overview of scene geometry and spatial relationships (Correct answer)
- Measuring the depth of tire yaw marks
- Documenting interior vehicle damage
Correct answer: Providing an overview of scene geometry and spatial relationships
Aerial drone photography provides a bird's-eye view that effectively documents the overall scene geometry, road layout, and spatial relationships between evidence items.
Question 6: What is the significance of a 'gap' in a continuous tire mark at a crash scene?
- It indicates the tire was skidding with ABS activation cycles
- It shows the vehicle was airborne or the wheel momentarily lifted (Correct answer)
- It marks the point where the tire went flat
- It confirms the driver attempted to steer during braking
Correct answer: It shows the vehicle was airborne or the wheel momentarily lifted
A gap in an otherwise continuous tire mark typically indicates that the wheel lifted off the pavement momentarily, such as during a bounce or rollover sequence.
Question 7: In crash scene documentation, a 'benchmark' or control point is used primarily to:
- Mark the location of the vehicles' final rest positions
- Provide a fixed reference for coordinate measurements throughout the scene (Correct answer)
- Indicate the area where perishable evidence was collected
- Record the investigating officer's position during photography
Correct answer: Provide a fixed reference for coordinate measurements throughout the scene
A benchmark or control point serves as a fixed, known reference location from which all coordinate measurements in the scene are taken and tied together.
ACTAR Evidence Documentation & Interpretation 2
When photographing tire marks at a crash scene, which lighting technique best reveals surface texture and mark depth?