CFC Bloodstain Pattern Analysis 3 — Questions and Answers
Question 1: When reconstructing a bloodstain scene, a 'void' pattern is significant because it suggests:
- An area where blood pooled due to gravity
- An object or person was present and blocked blood deposition (Correct answer)
- A region where blood was cleaned after the event
- A surface that is non-absorbent and repelled blood
Correct answer: An object or person was present and blocked blood deposition
A void pattern is a bloodstain-free area within otherwise consistent spatter, indicating that an object or person shielded that surface from blood at the time of the event.
Question 2: What effect does surface texture have on bloodstain morphology?
- Rough surfaces produce rounder stains with less spatter
- Smooth surfaces produce irregular edges with more satellite drops
- Rough surfaces produce more irregular edges and satellite spatter (Correct answer)
- Texture has no measurable effect on stain shape
Correct answer: Rough surfaces produce more irregular edges and satellite spatter
Rough or porous surfaces cause blood droplets to produce more irregular, scalloped edges with additional satellite spatter due to increased surface energy and disruption of the droplet.
Question 3: A 'wipe' pattern differs from a 'swipe' pattern in that a wipe:
- Is created by a moving bloody object contacting a clean surface
- Results from a clean object moving through existing wet blood (Correct answer)
- Shows the direction of movement by feathering on the leading edge
- Occurs only when blood is still fully liquid and unclotted
Correct answer: Results from a clean object moving through existing wet blood
A wipe pattern is produced when a clean object moves through existing wet blood, while a swipe is produced when a bloody object contacts a clean surface.
Question 4: In court testimony, a BPA expert using the term 'consistent with' rather than 'caused by' is:
- Weakening their testimony beyond usefulness
- Appropriately reflecting the probabilistic nature of physical evidence interpretation (Correct answer)
- Violating the Daubert standard by being imprecise
- Admitting that the analysis is inconclusive
Correct answer: Appropriately reflecting the probabilistic nature of physical evidence interpretation
Physical evidence interpretation is inherently probabilistic; 'consistent with' accurately conveys that the evidence supports a hypothesis without overstating certainty.
Question 5: Which bloodstain pattern would most strongly suggest a body was moved after blood had begun to pool?
- Satellite spatter around a pool
- Drag pattern with smearing and trail (Correct answer)
- Flow pattern following gravity down a vertical surface
- Cast-off on a nearby wall
Correct answer: Drag pattern with smearing and trail
A drag pattern with smearing and blood trail indicates a body or object was moved through pooled blood, redistributing it in the direction of movement.
Question 6: The 'string method' in BPA is used to determine:
- The bloodstain width-to-length ratio
- The area of origin in three-dimensional space (Correct answer)
- Whether blood was transferred by contact
- The approximate time of the bloodshed event
Correct answer: The area of origin in three-dimensional space
The string method uses physical strings along calculated trajectory angles from multiple stains to converge at the three-dimensional area of origin.
Question 7: High-velocity impact spatter (HVIS), historically associated with gunshot wounds, is characterized by:
- Stains averaging 3–5 mm in diameter
- Misting with very fine droplets often less than 1 mm (Correct answer)
- A fan-shaped pattern with large central stain
- Circular stains with heavy scalloping
Correct answer: Misting with very fine droplets often less than 1 mm
HVIS produces a mist of very fine droplets (often under 1 mm), though modern BPA methodology cautions against using velocity categories to determine mechanism without corroborating evidence.
CFC Bloodstain Pattern Analysis 3
When reconstructing a bloodstain scene, a 'void' pattern is significant because it suggests: