Blood Spatter
and
Crime Scene Reconstruction
What is blood?
Blood Typing: Class Data
Sample Blood Group Frequencies
Interlude
The Real CSI
First Determine: Is it Blood?
Kastle-Meyer Test
Blue Star®
Luminol
Leucomalachite
Is it Human?
ELISA (enzyme linked immunosorbent Assay
What Blood pattern analysis reveals
Origin of the bloodstain
Distance between blood source and target
Direction of travel and impact angles of droplets
Type of force used to cause bloodshed
Type of object used
Sequence of multiple bloodshed events
Contact and transfer patterns
Blood
Spatter
Blood Spatter
Overview
andforce
Criminal
Activity
PatternsDependence
produced when
is applied
to blood
Types / Classification
Methods
of Identification
Physical properties
of blood
Collection
and Preservation of Evidence
Blood is a fluid
droplets round up in air
flattened contacting surfaces
2 Main Types of Blood Patterns
Spatter Patterns–impact pattern of blood droplets
Why spatter looks the way it does Slomo
spatter
Transfer Patterns–from one surface to another
Droplet Size and Shape
Size (0.3 – 0.5 mm diameter)
Distance traveled
Texture of surface
Direction Traveled
Angle of impact
Origin of Impact
Velocity (Low, Medium, High)
Texture of Surface
Smooth surface (glass, marble)
Circular
Uniform
Porous surface
irregular shape
spikes and satellites
Spike
Satellite
Direction of Spatter
Low impact spatter
90o impact angle
no tail
Higher impact spatter
tail
points in direction of travel
Angle of Impact
The larger the angle of impact, the longer the tail
Convergence Point (2D) and
Origin of Impact (3D)
Convergence
Crime Scene
exercise
Determining Angle of Impact
Determining the angle of impact:
measure width (W), length (L)
Solve: 𝜃 =
𝑊
−1
𝑠𝑖𝑛
𝐿
Point of Origin (3D)
Spatter Patterns
Impact pattern of blood droplets
function of speed and energy of droplets
3 main types:
high velocity
medium velocity
low velocity
High Velocity Spatter Patterns
Droplet size < 2mm diameter – “mist like”
Impact force > 100 ft/sec
Gunshots, explosions and high speed collisions
Short travel distance
High Velocity Gun Shot Spatter
Back spatter - toward gun
forward spatter - in bullet direction
Amount of spatter
Caliber of bullet
larger bullet, more spatter
Distance
closer, more spatter
Why
back
spatter?
Medium Velocity Spatter Patterns
Droplet size: 2mm – 4mm diameter
Impact force > 25 ft/sec
Blunt force, stabbing and secondary spatter
Low Velocity Spatter Patterns
Droplet size: > 4mm diameter
Large, circular shape
Velocity due to gravity
open wounds, saturated surfaces
increase size with distance (see earlier slide)
Cast Off Spatter Patterns
Blood covered object flings blood into the air
handedness
number of blows
direction of impact
amount of blood
Contact Patterns
a wet bloody surface contacts another surface
Types of transfer:
Transfer -
a recognizable image is formed
Swipes -
wet blood is transferred to a surface
wipes -
“clean” object moves through blood
Other Spatter Patterns
Arterial Spray Spatter
Expirated Blood Spatter
Voids
Documenting Blood Patterns Evidence
Overview Photo - each pattern
Note, sketch and photograph
droplets used to do point of origin calculations
droplet samples sent to lab for analysis