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Lesson 6 Blood Spatter Analysis

Lesson 6 Blood Spatter Analysis

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Lesson 6 Blood Spatter Analysis

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  1. Lesson 6Blood Spatter Analysis

  2. Activity 6.1 Seeing red blood spatters http://www.crimescene-forensics.com/Blood_Stains.html (Crime Scene Forensics, LLC, New York)

  3. Blood spatter 2 Blood spatter 1 • What are the differences between the boundaries of the two blood spatters? • What may be the causes of the differences?

  4. Activity 6.1 Seeing red blood spatters

  5. Activity 6.1 Seeing red blood spatters Results: a) Plastic CD case b) Table cloth c) Glass plate d) Sponge

  6. Activity 6.1 Seeing red blood spatters Results: e) Heat proof mat f) Bandage g) Cardboard h) Newspaper

  7. 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, Activity 6.1 Seeing red blood spatters Interpretation and Deduction:

  8. Activity 6.1 Seeing red blood spatters Interpretation and Deduction: 1. Shape of Blood Spatter Description of shape and boundary: Round shape, Smooth and regular boundary Description of shape and boundary: Round shape Jagged & irregular boundary Materials you have used: Plastic CD, Glass plate, Card board Materials you have used: Heat proof mat, Table cloth, Sponge, Bandage, Newspaper

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

  10. 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: jagged and irregular boundary jagged and irregular boundary smooth and regular boundary smooth and regular boundary

  11. 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.

  12. 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) ?

  13. Short axis Long axis Direction of motion Satellite spatter Activity 6.2 Directionality of Impact 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)

  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)

  15. 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) (HowStuffWorks, Inc.)

  17. Angle of Impact = arcsin (width/length)

  18. Activity 6.3 Angle of Impact 1. Mathematical formula of angle of impact Source: http://www.crimescene-forensics.com/Blood_Stains.html (Crime Scene Forensics, LLC, New York) b) Find the angle of impact for the blood spatter in figure 2 sin q = = q= 30o Figure 2

  19. Activity 6.3 Angle of Impact 2. Finding the angle of impact of a blood spatter Part I. Making a spatter

  20. q = 8o q = 13o Activity 6.3 Angle of Impact 2. Finding the angle of impact of a blood spatterWhich measurement is correct?

  21. Long axis Short axis Activity 6.3 Angle of Impact 2. Finding the angle of impact of a blood spatter Part II. Calculating the angle of impact sin q = Blood spatter Blood spatter Step 1 Step 1 Step 1 Step 2 Step 2 Step 2 Step 2 Step 3 Step 3 Step 3 Step 3

  22. Lies between 6 to 7 mm Linear match between small scale and main scale at 0.35 mm 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

  23. Activity 6.3 Angle of Impact 2. Finding the angle of impact of a blood spatter Result

  24. 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)

  25. Activity 6.4 Case Reconstruction

  26. Activity 6.4 Case Reconstruction

  27. Activity 6.4 Case Reconstruction

  28. Area of convergence

  29. Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part I. Making a blood spatter Video: Preparing bloody sponge Video: Dropping hammer

  30. Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part I. Making a blood spatter

  31. 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

  32. 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

  33. Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 2

  34. 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

  35. Imagine an oval that encloses the blood spatter 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 Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 4 The distance between the pin and the front edge of oval is equal to the diameter of the pin

  36. 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

  37. 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) Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 6

  38. 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

  39. Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 8 Suspend strings from all the blood spatters

  40. 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

  41. 3 2 2 1 1 4 5 8 9 6 10 Distance of A from vertical surface: Y = 16 cm 7 Distance of B from vertical surface: Y = 9 cm Height: Z = 14.5 cm Height: Z = 7.5 cm Measure the distance of the origin from the vertical and horizontal surfaces Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 10

  42. 3 2 2 1 1 4 5 8 9 6 10 Distance from surface: 16 cm 7 Distance from surface: 9 cm Height: 14.5 cm Height: 7.5 cm Activity 6.4 Case Reconstruction 1. Finding the Point of Origin 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(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

  43. 3 2 2 1 1 4 5 8 9 6 10 Distance from surface: 16 cm 7 Distance from surface: 9 cm Height: 14.5 cm Height: 7.5 cm Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 10 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

  44. 3 2 2 1 1 4 5 8 9 6 10 Distance from surface: 16 cm 7 Distance from surface: 9 cm Height: 14.5 cm Height: 7.5 cm Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Stringing method-Step 10 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 by swinging of hammer in air.

  45. 3 2 2 1 1 4 5 8 9 6 10 Distance from surface: 16 cm 7 Distance from surface: 9 cm Height: 14.5 cm Height: 7.5 cm Activity 6.4 Case Reconstruction 1. Finding the Point of Origin Part II. Reflection What kinds of human qualities or attributes are essential for successful achievement of case reconstruction? • 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

  46. http://hemospat.com/index.php Source: HemoSpat

  47. Activity 6.4 Case Reconstruction 2. Using computer programs HemoSpat Demo

  48. Activity 6.4 Case Reconstruction 2. Using computer programs HemoSpat Demo