Chapter Ten –
Bloodstain Pattern
Analysis
FRSC 8104
Criminalistics II
Professor Bensley
FRSC 8104 – Bloodstain Pattern
Objectives
1.
2.
3.
4.
5.
6.
7.
Discuss the information that can be gained from bloodstain pattern
analysis about the events involved in a crime.
Explain how surface texture, directionality, and angle of impact affect the
shape of individual bloodstains.
Calculate the angle of impact of a bloodstain using its dimensions.
Describe the classifications of low-, medium-, and high-velocity impact
spatter and appreciate how those classifications should be used.
Discuss the methods to determine the area of convergence and area of
origin for impact spatter patterns.
Understand how various blood pattern types are created and which
features of each pattern can be used to aid in reconstructing events at a
crime scene.
Describe the methods for documenting bloodstain patterns at a crime
scene.
FRSC 8104 – Blood Spatter Outline
I. Introduction
A. What is it?
B. What can we learn from interpretations?
II. Properties of Blood
A. Basic Properties
B. Shape of Drops
1.
Surface Tension
Way Cool Videos!
FRSC 8104 – Blood Spatter Outline
C. Volume of blood drops
D. Diameter of Stain vs. Distance Fallen
1.
Maximum Terminal Velocity
Videos 1 and 2
A high-speed photograph time series comparing the impact dynamics of three different droplet diameters.
Impact velocity was 4.2 m/s and the surface was paper.
http://www.hartnell.cc.ca.us/faculty/jhughey/Files/bloodstainshapes.pdf
FRSC 8104 – Blood Spatter Outline
III. Bloodstain Formation and Impact Angle
A. Direction of Travel
B. Angle of Impact Determinations
1.
We love Trigonometry!
Videos – 80 degrees (Top View)
80 degrees (Side View)
20 degrees (Top View)
20 degrees (Side View)
Angle of Impact
Angle of Impact
SIN < = Width (a) 1.5cm
Length (c) 3.0cm
Width (a) 1.5cm = SIN <
Length (c) 3.0cm
0.5 = SIN <
< = 30 degrees
FRSC 8104 – Blood Spatter Outline
IV. Locating the Source of Bloodstains
A. Point (AREA) of convergence
http://www.fbi.gov/publications/leb/2005/feb2005/feb2005_img_31.jpg
Video of Rat Trap at less than a 5 degree
angle for Point of Convergence
FRSC 8104 – Blood Spatter Outline
B. Point (AREA) of origin
1.
2.
3.
4.
Stringing Method
Trigonometry
Graph Paper
Computer (BPA
Software)
C. Limitations
1.
2.
Assume straight lines
of travel
Surfaces other than
horizontal
FRSC 8104 – Blood Spatter Outline
V. Altering a Drop of Blood
A. Changes in volume or changes in shape of
resultant pattern
B. What are goals of BPA?
C. Various target surfaces
1.
2.
3.
4.
Texture
Thickness
Absorbency
Hardness
Blood Striking Various Surfaces
Smooth, NonPorous Surface
(Glass)
Linoleum
Cement Board
Videos of Surfaces – Cotton, Wood, Cement
FRSC 8104 – Blood Spatter Outline
D. Forces Acting upon Blood
1.
Low velocity impact spatter
a. Blood dripping into blood
b. Splashed blood
• Gravitational pull up
to 5 feet/sec.
• Relatively large stains
4mm in size and
greater
Videos:
#1
#2
FRSC 8104 – Blood Spatter Outline
2.
Medium velocity impact spatter
a. Beating or stabbing
• Force of 5 to 25
feet/sec.
• Preponderant stain
size 1 to 4mm in
size
Videos:
#1
#2
FRSC 8104 – Blood Spatter Outline
3.
High velocity impact spatter
a. Gunshots, Explosions, Mechanical Accidents
• Force of 100 feet/sec.
and greater
• Preponderant stain
size 1mm in size and
smaller
• Mist like appearance
Videos:
#1
#2
FRSC 8104 – Blood Spatter Outline
b.
Back spatter vs. Forward spatter
FRSC 8104 – Blood Spatter Outline
4.
Projected Blood Pattern
a. Running in, stamping in, or slapping a pool of blood
b. Beating a head on the floor
c. Arterial gushing or spurting
FRSC 8104 – Blood Spatter Outline
5.
Cast Off Blood Patterns
a. Blood being cast from a bloody object in motion
onto a target surface
b. Swinging a bloody hand or weapon
c. Minimum number of blows delivered
d. Technically not spatter
Videos:
#1
#2
#3
FRSC 8104 – Blood Spatter Outline
VI. Other Patterns
A. Transfers
FRSC 8104 – Blood Spatter Outline
B. Void Patterns
FRSC 8104 – Blood Spatter Outline
C. Sequence of Events
D. Swipes
vs. Wipes
Video of Swiping Fingers
Feathering Indicates
Direction of Travel of
Swipe
FRSC 8104 – Blood Spatter Outline
E. Time-Lapse Drying
1.
Skeletonizing
FRSC 8104 – Blood Spatter Outline
F. Time-Lapse Clotting (Serum Stains)
http://www.softchalk.com/lessonchallen
ge/lesson/ImmuneSystems/index.html
FRSC 8104 – Blood Spatter Outline
G. Diluted Stains
H. Expiratory Blood
1.
Sneezes, Coughs, Gurgles, Sucking chest wounds, etc.
Videos: #1, #2, #3
I.
Skipping Patterns