1 Lesson 6 Blood Spatter Analysis. 2 Activity 6.1 Seeing red blood spatters (Crime Scene Forensics,

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Lesson 6Blood Spatter Analysis

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Activity 6.1 Seeing red blood spatters

http://www.crimescene-forensics.com/Blood_Stains.html(Crime Scene Forensics, LLC, New York)

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1. What are the differences between the boundaries of the two blood spatters?

2. What may be the causes of the differences?

Blood spatter 1 Blood spatter 2

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Results:

a) Plastic CD case

c) Glass plate

b) Table cloth

d) Sponge

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Results:

e) Heat proof mat

g) Cardboard

f) Bandage

h) Newspaper

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Shape of Blood Spatter

Description of shape and boundary:


Materials you have used: Materials you have used: Heat proof mat, Table cloth,


Interpretation and Deduction:

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Interpretation and Deduction:1.

Shape of Blood Spatter


Round shape, Smooth and regular boundary


Round shapeJagged & irregular boundary

Materials you have used:

Plastic CD, Glass plate,Card board

Materials you have used: Heat proof mat, Table cloth,

Sponge, Bandage, Newspaper

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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 round-shaped. The materials of contact surface do not have a direct influence on the shape of the blood spatter.

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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 b) sandy beach

c) the hood of a car d) floor tile

jagged and irregular boundary

smooth and regular boundary

jagged and irregular boundary

smooth and regular boundary

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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.

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Activity 6.2 Directionality of Impact

Source: http://www.crimescene-forensics.com/Blood_Stains.html (Crime Scene Forensics, LLC, New York)

1. To which direction did the blood move?Draw an arrow in the diagram to show its directionality of impact.

http://www.crimescene-forensics.com/Blood_Stains.html

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Which direction did the blood move?Draw an arrow in the diagram to show its directionality of impact.

Long axisShort axis

Direction of motion Satellite spatter


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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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2. Identifying the features of blood spatters

Write the names of features in the spaces provided.


Satellite Spatter

Spine

Scallop Pattern

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Angle of Impact = arcsin (width/length)

(HowStuffWorks, Inc.)

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Angle of Impact = arcsin (width/length)

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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

sin =

= = 30o

Length

Width

mm

mm

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Figure 2


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2. Finding the angle of impact of a blood spatter Part I. Making a spatter

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Activity 6.3 Angle of Impact 2. Finding the angle of impact of a blood spatter Which measurement is correct?

= 8o

= 13o

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2. Finding the angle of impact of a blood spatter Part II. Calculating the angle of impact

sin = axislongoflength

axisshortoflength

___

___

Long axis

Short axis

Blood spatter Step 1 Step 2 Step 3 Step 2 Step 3 Step 1 Step 2 Step 3 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

Linear match between small scale and main scale at 0.35 mm

Lies between 6 to 7 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

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Area of convergence

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Part I. Making a blood spatter

Video: Preparing bloody sponge

Video: Dropping hammer

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Identify some isolated blood spatters with clear edges

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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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Cut off the edge of a protractor below its centre

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Imagine an oval that encloses the blood spatter

The distance between the pin and the front edge of oval is equal to the diameter of the pin

Measure the radius of

the pin

The distance between the pin and the tailing edge of oval is equal to the radius of the pin

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The starting point of string is located at the tailing edge of the imaginary oval

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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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Fix the other end of the string on polystyrene board with another thumb pin or adhesive tape

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Suspend strings from all the blood spatters

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Locate the point of origin at a position where many strings cross over each other

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11223

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Distance of A from vertical surface:

Y = 16 cm

Distance of B from vertical surface:

Y = 9 cm

Height: Z = 14.5 cm

Height: Z = 7.5 cmMeasure the distance of the origin from the vertical and horizontal surfaces

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1. Finding the Point of Origin


Location of Origin:Two origins were found.Location of Origin A:

Perpendicular distance from vertical surface: 16 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 cmHeight: 14.5 cm

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Distance from surface: 16 cm Distance from

surface: 9 cm

Height: 14.5 cm

Height: 7.5 cm

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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

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surface: 9 cm

Height: 14.5 cm

Height: 7.5 cm

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Conclusion:The point of origin of a blood spatterhad 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 by swinging of hammer in air.

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223

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surface: 9 cm

Height: 14.5 cm

Height: 7.5 cm

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Part II. Reflection

What kinds of human qualities or attributes are essential for successful achievement of casereconstruction?

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223

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6Distance

from surface: 16

cm

Distance from

surface: 9 cm

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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Source: HemoSpat

http://hemospat.com/index.php

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2. Using computer programsHemoSpat Demo

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Activity 6.4 Case Reconstruction 2. Using computer programs HemoSpat Demo

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2. Using computer programs HemoSpat Demo

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2. Using computer programs HemoSpat Demo

1 Lesson 6 Blood Spatter Analysis. 2 Activity 6.1 Seeing red blood spatters (Crime Scene Forensics,

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