Blood Spatter
Analysis
Blood Spatter (not splatter)
is the pattern of blood
created when blood is
deposited on a surface.
History of Blood-Spatter Analysis
•  1894 – Pitoroski wrote the earliest reference on
blood-spatter analysis
•  1939 – Blathazard was the first researcher to
analyze the meaning of the spatter pattern
•  1955 – blood-spatter evidence was used by the
defense in the Sam Shepard case, eventually
exonerating him
•  1971 Dr. Herbert MacDonnell used blood-spatter
analysis as a tool in modern forensic
examinations.
Blood Detection
•  Phenolphthalein
•  Luminol
Blood spatter “tells a story”
•  Where was person located when
bleeding?
•  What direction was blood
traveling?
•  What was the angle of impact?
What was the
distance
between
bleeder and
the striking
surface?
• How many
events
occurred?
Blood Spatter
•  Used to explain events at a violent crime
scene
–  Direction blood travels
–  Angle of impact
–  Blood velocity (manner of death)
–  Point of origin
Physical Properties
•  Cohesion - blood sticks together as it falls
•  Gravity - pulls blood downward
•  Surface tension - blood drops that fall on a
flat surface have a curved surface
•  Edges may have spikes or extensions
•  Satellites - small secondary droplets
6 patterns of blood spatter
1.  Passive fall (90o angle to floor)– circular drops
w/secondary satellites
2.  Arterial spurts or gushes
3.  Splashes – show position of victim
4.  Smears – bleeding victim touching walls or
furniture
5.  Blood Trails – victim moving from one place to
another
6.  Blood Pools – victim bleeds heavily
splash
arterial
spurts
passive fall
blood pool
multiple
drips
smear
•  Cast off pattern: blood from a
moving object coated in blood
(pipe, knife)
•  Fine-mist spatter: high-velocity
impact (gunshot)
•  Void: empty space; victim/
attacker/object moved after attack
Blood Spatter Types
1.  High velocity – gunshot wounds
2.  Medium velocity – beating, stabbing
3.  Low velocity – blunt object impact
Lines of Convergence
•  Location of the source of blood can be
determined if there are at least two drops of blood
spatter
•  Determine source of blood (point of origin)
•  Draw straight lines down long axis of blood
spatter where lines intersect will indicate the lines
of convergence
Crime-Scene Investigation of Blood
1.  Confirm the stain is blood.
Ø  Visualization with Luminol
Ø  Kastle-Meyer test – if present a dark pink
color is produced
Ø  Leukomalachite green – produces green
color in the presence of blood
2.  Confirm the stain is human.
Ø  ELISA test – Enzyme Linked
Immunosorbent Assay
3.  Determine blood type.
Ø  Antibody test
Simpson Crime Scene
Is blood spatter evidence
consistent with the story told
by witness or suspect?
Characteristics of a single
drop of blood
Spike vs. satellite
Surface variations
Smooth
(glass)
Slightly
raised
floor tiling
varnished
wood,
fabric
Rough tile
unvarnished
wood
Blood dropped from different
heights
Transferred blood
Footprint
Handprint
Patterns of transfer
ceiling
Cast-off from Weapon
Direction of travel of blood
Wave Cast-off
Tail of elongated stain
points in direction of travel
.
Tail of wave cast-off points
back to parent drop
Parent drop
wave cast-off
5 ml blood squirted from a
syringe from height of 1 m
Point of Convergence
Point of Convergence
Lines of Convergence
•  Draw line through the axis of the main
droplet
•  Start at the end of the blood drop and
draw toward the source
•  Do not draw lines through satellite drops
•  Draw smallest circle around intersection marks point of convergence
Lines of
Convergence
Determine
Point of
Convergence
Don’t over
extend the
lines!
Draw
towards the
source of
blood
Let’s practice!
Answer Sheet for Lines of Convergence
Height above point of convergence
Angle of Impact
Origin
length
width
Angle of impact = arc sin W/L
85°
60°
45°
Distance from point of convergence
30°
Determine Angle of Impact
Width
Length
sine
arc sine
42°
2
3
.6667
1
4
.25
14.5°
9.6
9.7
.9897
82.2°
Angle
of
Impact
W
Path of blood
90°
60°
80°
50°
a
70°
40°
l
l
Floor
30°
20°
10°
Practice Paper Blood Droplets
•  Draw lines of convergence
•  Determine point of convergence
•  Measure blood drop width/length
•  Determine impact angle
Can you
determine
point of origin?
Tracing Origin of
Bloodspots
•  Point of convergence
–  2 dimensional image
•  Point of origin
–  adds 3rd dimension to image
•  In practice:
–  use of string & protractor at
scene
–  use of computer at laboratory
Calculate Point of Origin
• Draw lines of convergence
• Determine point of convergence
• Determine impact angle
• Use protractor to determine origin
Or
Use Law of Tangents
Law of Tangents (TOA)
Tangent of Angle =
Opposite
Adjacent
mm
mm
H
E
I
X
G
Y
H
T
XJ
Distance
Thanks for coming