Lesson 6
Blood Spatter Analysis
1
Activity 6.1
Seeing red blood spatters
http://www.crimescene-forensics.com/Blood_Stains.html
(Crime Scene Forensics, LLC, New York)
2
Blood spatter 1
Blood spatter 2
1. What are the differences between the boundaries of the two
blood spatters?
2. What may be the causes of the differences?
3
Activity 6.1
Seeing red blood spatters
4
Activity 6.1
Seeing red blood spatters
Results:
a) Plastic CD case
b) Table cloth
c) Glass plate
d) Sponge
5
Activity 6.1
Seeing red blood spatters
Results:
e) Heat proof mat
f) Bandage
g) Cardboard
h) Newspaper
6
Activity 6.1
Seeing red blood spatters
Interpretation and Deduction:
Shape of Blood Spatter
Description of shape and boundary:
Description of shape and boundary:
Materials you have used:
Materials you have used:
Heat proof mat, Table cloth,
7
Activity 6.1
Seeing red blood spatters
Interpretation and Deduction:
1.
Shape of Blood Spatter
Description of shape and boundary:
Description of shape and boundary:
Round shape,
Smooth and regular
boundary
Round shape
Jagged & irregular
boundary
Materials you have used:
Materials you have used:
Heat proof mat, Table cloth,
Plastic CD, Glass plate,
Card board
Sponge, Bandage,
Newspaper
8
Activity 6.1
Seeing red blood spatters
2. Deduce how the materials of the surface
influence the shapes and boundaries of the
blood spatters?
A non-porous smooth surface gives a blood
spatter with smooth and regular boundary.
A porous rough surface gives a blood spatter
with jagged and irregular boundary.
All of the blood spatters are nearly roundshaped. The materials of contact surface do not
have a direct influence on the shape of the
blood spatter.
9
Activity 6.1
Seeing red blood spatters
3. Based on your classification and deduction, predict what kind of
boundaries the blood spatter will have if blood is dropped onto the
following surfaces:
a)Cotton
jagged and
irregular boundary
c) the hood of a car
smooth and
regular boundary
b) sandy beach
jagged and
irregular boundary
d) floor tile
smooth and
regular boundary
10
Activity 6.1
Seeing red blood spatters
Conclusion:
Write a few sentences to conclude your findings
in this experiment.
Free-falling blood drops tend to form circular blood
spatters. The materials of contact surfaces do
not influence the shape of the blood spatters.
A non-porous smooth surface gives a blood
spatter with smooth and regular boundary.
A porous rough surface gives a blood spatter with
jagged and irregular boundary.
11
Activity 6.2
Directionality of Impact
1. To which direction did the blood move?
Draw an arrow in the diagram to show its directionality of impact.
Source: http://www.crimescene-forensics.com/Blood_Stains.html
(Crime Scene Forensics, LLC, New York)
12
Activity 6.2
Directionality of Impact
Which direction did the blood move?
Draw an arrow in the diagram to show its directionality of impact.
Short axis
Long axis
Direction of motion
Satellite spatter
Source: http://www.crimescene-forensics.com/Blood_Stains.html
(Crime Scene Forensics, LLC, New York)
13
14
Source:http://science.howstuffworks.com/bloodstain-pattern-analysis3.htm (HowStuffWorks, Inc.)
Notes:
Scallop pattern - bloodstain produced by a single blood droplet characterised by a wave-like, scalloped edge.
Satellite spatters - small droplets of blood projected around a drop of blood upon impact with a surface.
Spines – pointed edge characteristics that radiate away from the centre of a bloodstain; dependent on impact velocity and surface texture.
(Reference: http://www.tipton-county.com/bhs/teachers/lwitherington/terms.pdf)
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Activity 6.2
Directionality of Impact
2. Identifying the features of blood spatters
Write the names of features in the spaces provided.
Spine
Satellite
Spatter
Scallop
Pattern
16
Angle of Impact = arcsin (width/length)
17
(HowStuffWorks, Inc.)
Angle of Impact = arcsin (width/length)
18
19
Activity 6.3 Angle of Impact
1. Mathematical formula of angle of impact
b)
Find the angle of
impact for the blood
spatter in figure 2
Width
sin q =
Length
9mm
=
18 mm
q=
30o
Figure 2
Source: http://www.crimescene-forensics.com/Blood_Stains.html
(Crime Scene Forensics, LLC, New York)
20
Activity 6.3 Angle of Impact
2. Finding the angle of impact of a blood spatter
Part I. Making a spatter
21
Activity 6.3 Angle of Impact
2. Finding the angle of impact of a blood spatter
Which measurement is correct?
q = 8o
q = 13o
22
Activity 6.3 Angle of Impact
2. Finding the angle of impact of a blood spatter
Part II. Calculating the angle of impact
length_ of _ short _ axis
sin q = length_ of _ long _ axis
Long axis
Short axis
Blood spatter
Step 1
Step 2
Step 3
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Activity 6.3 Angle of Impact
2. Finding the angle of impact of a blood spatter
Part II. Calculating the angle of impact
Using a venire caliper
Lies between
6 to 7 mm
Linear match between small
scale and main scale at 0.35 mm
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Activity 6.3 Angle of Impact
2. Finding the angle of impact of a blood spatter
Result
Group number
1
2
3
4
Length of short axis /
cm
0.52
1.035
1.190
1.570
Length of long axis /
cm
3.25
2.140
1.900
1.590
Angle of impact
9.20o
28.92o
38.70o
80.90o
Sketch of spatter
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
If you are given a blood spatter pattern, how can you
determine the point of origin?
How far is the point of origin from the target surface?
Source: http://www.crimescene-forensics.com/Blood_Stains.html
(Crime Scene Forensics, LLC, New York)
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Activity 6.4 Case Reconstruction
27
Activity 6.4 Case Reconstruction
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Activity 6.4 Case Reconstruction
29
Area of convergence
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part I. Making a blood spatter
Video: Preparing bloody sponge
Video: Dropping hammer
31
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part I. Making a blood spatter
32
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part I. Making a blood spatter
Identify some isolated blood
spatters with clear edges
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 1
Draw a long arrow to indicate the direction of origin (opposite to the
direction of impact) and mark the angle of impact at each spatter
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 2
35
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 3
Cut off the edge of a protractor below its centre
36
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 4
Imagine an oval that encloses
the blood spatter
The distance between the pin and
the tailing
front edge
edgeofofoval
ovalisisequal
equaltoto
the radius
diameter
of the
of the
pinpin
Measure the radius of
the pin
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 5
The starting point of string is
located at the tailing edge of
the imaginary oval
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 6
The centre of protractor aligns with starting point of string
The plane of protractor
lies along with the
direction of impact
The string is
suspended at
the angle of
impact (54o)
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Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 7
Fix the other end of the string on polystyrene
board with another thumb pin or adhesive tape
40
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 8
Suspend strings from all the blood spatters
41
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 9
Locate the point of origin at a position where
many strings cross over each other
42
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
Part II. Stringing method-Step 10
3
4
5
2
1
8
9
6
10
Distance of A from
vertical surface:
Y = 16 cm
Distance of B from
vertical surface:
Y = 9 cm
7
Height: Z = 14.5 cm
Height: Z = 7.5 cm
Measure the distance of the origin from the
vertical and horizontal surfaces
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Activity 6.4 Case Reconstruction
4
5
1. Finding the Point of Origin
3
2
1
2 1
8
9
6
10
Distance from
surface: 16 cm
Distance from
surface: 9 cm
7
Part II. Stringing method-Step 10
Location of Origin:
Two origins were found.
Location of Origin A:
Perpendicular distance from vertical surface: 16 cm
Height: 7.5 cm
Height: 14.5 cm
Height: 7.5 cm
(the actual position of sponge is 15 cm from the paper)
Location of Origin B:
Perpendicular distance from vertical surface: 9 cm
Height: 14.5 cm
44
Activity 6.4 Case Reconstruction
1. Finding the Point of Origin
4
5
3
2
1
2 1
8
9
Part II. Stringing method-Step 10
6
10
Distance from
surface: 16 cm
Distance from
surface: 9 cm
7
Height: 14.5 cm
Height: 7.5 cm
Explanation:
When hammer hit the sponge, a primary origin was
produced to form the blood spatters at labels 4, 5, 6, 8, 9.
The hammer might swing in air to produce a second origin
to form the blood spatters at labels 1, 2, 3, 7, 10
45
Activity 6.4 Case Reconstruction
4
5
1. Finding the Point of Origin
3
2
1
2 1
8
9
6
10
Distance from
surface: 16 cm
Part II. Stringing method-Step 10
Distance from
surface: 9 cm
7
Height: 14.5 cm
Height: 7.5 cm
Conclusion:
The point of origin of a blood spatter
had been found by using stringing technique.
The directionality and angle of impact of each blood spatter were
determined. Then a string was suspended from each spatter
according to the calculated information.
The position where most strings were crossing each other
indicated the position of the origin.
In this experiment, two origins were found. The first origin was
the primary source of impact. The second origin would be caused
46
by swinging of hammer in air.
Activity 6.4 Case Reconstruction
4
5
1. Finding the Point of Origin
Part II. Reflection
What kinds of human qualities or attributes are
essential for successful achievement of case
reconstruction?
3
8
2
1
2 1
9
6
10
Distance
from
surface: 16
cm
Distance
from surface:
9 cm
7
Height: 14.5
cm
Height: 7.5
cm
-Knowledgeable in forensic science and other fields of science
-Adopt interdisciplinary thinking
-Objective, evidence-based
-Well-organized, systematic
-Attentive, patient, having keen observation
-Logical, flexible and creative minded
-Frequently reviewing and checking for mistakes
-Ready for challenges and failures
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http://hemospat.com/index.php
Source: HemoSpat
48
Activity 6.4 Case Reconstruction
2. Using computer programs
HemoSpat Demo
49
Activity 6.4 Case Reconstruction
2. Using computer programs
HemoSpat Demo
50
Activity 6.4 Case Reconstruction
2. Using computer programs
HemoSpat Demo
51
Activity 6.4 Case Reconstruction
2. Using computer programs
HemoSpat Demo
52
Activity 6.4 Case Reconstruction
2. Using computer programs
HemoSpat Demo
53
Activity 6.4 Case Reconstruction
2. Using computer programs
HemoSpat Demo
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