Chapter 4 presentation from Forensic Science 4th edition

1. Forensic Science: An
Introduction to Scientific
& Investigative
Techniques
Section 2: The Crime
Scene

2. Section 2: The Crime Scene
 Chapter 3: Crime Scene Investigation
 Chapter 4: Recognition of Bloodstain
Patterns

3. Chapter 4: Recognition of Bloodstain
Patterns
 4.1 Bloodstain Pattern Evidence
 4.2 History of Bloodstain Pattern Analysis
 4.3 Properties of Human Blood
 4.4 Formation of Blood
 4.5 Altered Bloodstains
 4.6 Analysis of Bloodstains on Clothing and Footwear
 4.7 Documentation of Bloodstain Evidence
 4.8 Absence of Evidence Is Not Evidence of Absence
 4.9 Training and Education

4. Bloodstain Pattern Evidence
 Forensic tool to assist
 Used to:
 Corroborate statements
 Apprehend suspects
 Interrogate suspects
 Reconstruction of scene
 Strengths and
weaknesses
 Only as valid as
information available
and examiners abilities

5. History of Bloodstain Pattern Analysis
 1895 Dr. Eduard Piotrowski
 1939 Dr. Victor Balthazard
 1955 Dr. Paul Kirk
 1971-73 Herbert Leon MacDonell
 2002 SWGSTAIN

6. Properties of Human Blood
What are the biological
properties of
blood?

7. Properties of Human Blood
 Biological Properties:
 To tissues – Oxygen, electrolytes, nourishment,
hormones, vitamins, antibodies
 From tissues – Waste products
 Plasma → Red and White blood cells and
platelets
 Clotted plasma = serum
 Nuclei of WBC = DNA
 Healthy adults contain 4.5 – 6.0 liters

8. Physical Properties of Blood
Are all blood drops the
same size?
Why?

9. Physical Properties of Blood
 Held together by molecular
forces
 Surface tension = Force
Slightly less than water
 To create spatter surface tension must
be overcome by an external force
 Shape of drop in air is dependent upon
the molecular forces acting upon its
surface

10. Physical Properties of Blood
 Physical properties allow stability.
Viscosity = Resistance
 More viscous = moving more slowly
Specific Gravity = weight compared to H2O
 Terminal Velocity
Force down = force up

11. Formation of Bloodstains and Bloodstain
Patterns – Target Considerations
 Big Small
 Unless disruption of
surface tension
 Target texture
 Smooth – no spatter
 Rough – spatter

12. Size, Shape, and Directionality
 Directionality
 Direction of travel
 Determined through
geometry of stain
 Edge Characteristics
 Narrow end = direction
of travel

13. Size, Shape, and Directionality
 Area of Origin
 Location of blood source
 2D: Long Axes
 Draw straight lines through
long axes where they
converge is the relative
source location
 3D: Impact Angles
 Est. angles and project
trajectories back to
common axis, 90o
from the
2D area of convergence

14. Size, Shape, and Directionality
 Angle of Impact
 Ratio: Width ÷ Length
 Circular →Ratio = 1 →
impact 90o
 Elliptical → Ratio >1 →
impact >90o
 Example:
 Width = ½ Length
 Ratio = 0.5
 Sin-1
(0.5) = 30o

15. Spattered Blood
 Identify stain as spatter
before determining
mechanism
 Determining mechanism
usually requires more
information
 Factors
 Quantity
 Force
 Texture
Random distribution of bloodstains created when sufficient force is
available to overcome surface tension of blood

16. Impact Spatter Associated with Gunshot
What is the difference
between forward and back
spatter?

17. Impact Spatter Associated with Gunshot
 Mist-like dispersions
 Wide size range
 Factors: available blood,
caliber, location, number
of shots, and impeding
factors
 Similar patterns produced by
power tools, explosions,
machinery injuries,
automobile collisions

18. Impact Spatter Associated with Beating
and Stabbing
 Size: 1 to 3 mm in
diameter
 Exposed blood must
be present
 Number of blows
inflicted have effects
on the resulting
pattern

19. Significance of Satellite Spatters
Resulting from Dripped Blood
 Size: 0.1 to 2.0 mm in
diameter
 Factors: volume,
freshness, surface, and
distance
 Mechanism of spatter
causing these stains
should be thoroughly
explored
Satellite spatter - Smaller droplets of blood that have detached from the main blood
volume at the moment of impact

20. Castoff Bloodstain Patterns
 Size: varies greatly
 Appear linear in
distribution
 Seen in conjunction with
impact spatters
 NOT possible to
determine with certainty
the object used
Castoff patterns - created with subsequent blows to the same general area where a
wound has occurred and blood has accumulated

21. Bloodstain Patterns Resulting from Large
Volumes: Splashed and Projected Blood
 Splashed - excess of
1.0 mL subjected to
minor force
 Ricochet – secondary
blood splashing
 Projected - blood is
projected or released
as the result of force

22. Expirated Bloodstain Patterns
 Similar to those of
impact spatter from
beatings or gunshots
 Specific features:
 Vacuoles – ruptured
air bubbles
 Dilution from saliva or
nasal secretions
Expirated bloodstain pattern – forcefully expelled blood from the nose or mouth that has
accumulated in the lungs, sinuses, and airway passages of the victim as a result of
trauma

23. Arterial Bloodstain Patterns
 Size: varies from large
gushing to small spray
 Factors: severity of
injury, size and
location, position of
victim, and clothing
 Very distinctive due to
the overall quantity of
bloodstains observed.

24. Transfer Bloodstain Patterns
 Experimentation with
objects
 Chemically enhancing
 Minute transfer vs.
impact
Transfer pattern – occurs when an object wet with blood comes in contact with an
object or secondary surface

25. Altered Bloodstains
 Factors of drying: volume, surface texture,
and environmental conditions
 Accelerated by increased temperature,
low humidity, and increased airflow
 Drying visualized from the outside inward

26. Altered Bloodstains
 SKELETONIZED
 Center of a dried
bloodstain flakes away
and leaves a visible
outer rim
 Central area of a
partially dried
bloodstain is altered
by contact or a wiping
motion that leaves the
periphery intact

27. Altered Bloodstains
 CLOTTING
 Initiated when blood
exits the body and is
exposed to a foreign
surface
 Normal clotting time: 3 to
15 minutes
 Occurrence of
movement after a
significant interval of
time from the initial
bloodshed

28. Altered Bloodstains
 MOISTURE
Source:
 Outside elements
 Heat, fire, or smoke
 Cleaning with water or detergents or painted
Moisture dilutes existing bloodstains
 Use of chemical enhancement to locate

29. Altered Bloodstains
 VOID AREAS
 Absences of
bloodstains in
otherwise continuous
patterns of staining
 Source: Removal of
items

30. Analysis on Clothing and Footwear
 Two questions arise with bloodstained
garments:
Whose blood is on the garment?  DNA
How was the blood deposited onto the
garment?  Pattern analysis
 Passive bloodstaining
 Active bloodstaining

31. Analysis on Clothing and Footwear
 Steps for Examination:
 Establish the manner in which the garments were
collected, documented, and preserved prior to their
examination.
 Document the garments while the victim or suspect is still
wearing them, when possible.
 Allow the bloodstain analyst an opportunity to examine the
stains before their removal for DNA analysis.
 Take photographs
 Obtain a history of garment

32. Documentation
 More than one form of documentation
Photographs, video, diagrams and notes
 Size, shape, distribution, overall pattern
 Measuring devices within the photographs
 Microphotography
 Document to allow third party to utilize
 More is always better!

33. Absence
Is the absence of
evidence, evidence of
absence?

34. Absence
 Not uncommon for an assailant to have little if
any blood on themselves
 Absence should neither exonerate nor implicate
involvement
 Possible explanations:
 Protective outerwear
 Removed clothing
 Directionality away from the assailant

35. Training and Education
 Wide range of backgrounds
 Required 40 hour course
Key is hands on laboratory experiments
 Memberships
IABPA
 Est. 1983 with ~800 Members
 Journal of Bloodstain Pattern Analysis
THIS INSTRUCTIONAL UNIT IS NOT A BLOODSTAIN PATTERN
COURSE

36. Chapter 4 Summary
Found at most violent crime
scenes
Found, documented, analyzed,
and interpreted
Scientific analysis = invaluable
Dates back to 1800’s