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Forensic Science - 09 Blood and blood splatter

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A closer look at how blood and blood splatter is analysed in a forensic science investigation for Year 9 students at Saint Ignatius College Geelong

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Forensic Science - 09 Blood and blood splatter

  1. 1. DRYSDALE CSI Blood and blood splatter. Ian Anderson Saint Ignatius College Geelong
  2. 2. WHAT IS BLOOD?  Blood left at a crime scene can be analysed in several ways. Blood group/type can provide class evidence.  DNA profiling can determine whether blood left at a crime scene belongs matches the blood of a suspect (or victim).  Blood splatter can be used to help recreate a crime scene.  http://dungenie.com/forums/forum_posts.asp?TID=10639&PN=10
  3. 3. WHAT IS BLOOD? Average adult has about 5-6L of blood in their body.  Makes up approximately 9% of our body weight.  http://www.english-online.at/biology/blood/blood-supply-and-blood-diseases.htm
  4. 4. WHAT IS BLOOD?  Blood is composed of  Red blood cells (erythrocytes).   Carry oxygen to cells and carbon dioxide away from cells. White blood cells (leucocytes). Several different types.  Involved in defence and immunity  fighting pathogens (disease causing organisms)   Platelets.   Involved in blood clotting. Plasma.  90% water and remainder made up of dissolved proteins, hormones, sugars, amino acids, vitamins, minerals, urea, antibodies, etc.
  5. 5. WHAT IS BLOOD?  Blood has several important functions, including      Carries oxygen to cells. Carries waste (including carbon dioxide, urea & lactic acid) away from cells. Carries disease fighting cells. Involved in blood clotting. Involved in homeostasis. Regulation of body pH.  Regulation of core body temperature. 
  6. 6. BLOOD GROUPS. Blood from one person does not always freely mix with blood from another person. Instead, clumping might occur, which can result in death.  In 1901 Karl Landsteiner found that this response was due to the presence or absence of antigens (proteins on the surface of red blood cells), and is now used to classify a person’s blood type (ABO system).  A = only has antigen A.  B = only has antigen B.  AB = has both antigens A and B.  O = has neither antigens A or B. 
  7. 7. BLOOD GROUPS.  These blood types contain antibodies that react against the antigens. Blood group Antibody in plasma A A antigen anti-B B B antigen anti-A AB A & B antigens no antibodies O  Red blood cells contain no antigens anti-A & anti-B Every person belongs to one of these four blood groups for their whole life.
  8. 8. BLOOD GROUPS.  These blood types contain antibodies that react against the antigens. Blood Group Population A B AB O Aborigines 0 0 34 Australian (nonaboriginal) 39 11 4 46 UK/USA 41 10 4 45 Polynesian 52 0 0 48 Peruvian Indian  66 0 0 0 100 Your blood type is not necessarily unique to you, but is associated with a group of people.  Therefore blood type is regarded as class evidence.
  9. 9. BLOOD GROUPS.  Other blood grouping factors are also now used, incl.  Rh factor.   MN proteins.   ~82% of Australians Rh+ and 18% are Rh-. ~30% of people MM, 22%NN, 48% MN. Combining these other blood grouping factors, somebody can now be placed into one of 288 different blood types. http://www.smosh.com/smosh-pit/articles/blood-typing-japanese-zodiac
  10. 10. DNA PROFILING. DNA collected from white blood cells can be used for DNA profiling (also called DNA fingerprinting).  DNA profiling allows a blood sample to be identified with a single person.  http://blog.canacad.ac.jp/bio/BiologyIBHL1/1298.html
  11. 11. BLOOD SPLATTER. When a wound is inflicted and blood leaves the body, a blood splatter pattern may be created. This pattern can then be used to help reconstruct the series of events surround the shooting, stabbing or beating.  The characteristics of blood drops on surfaces can  Show how the blood was deposited  At what rate the blood was moving  The location of the origin or source of blood  The direction in which the blood was moving when it struck the surface. 
  12. 12. BLOOD SPLATTER.

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