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Blood and Blood Spatter

Blood and Blood Spatter. Serology. Blood Spatter Analysis. Serology. Examples: Blood Saliva Sweat Etc. What is serology?. Serology is the study of serums. Ludwig Tessnow Case.

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Blood and Blood Spatter

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  1. Blood and Blood Spatter Serology Blood Spatter Analysis

  2. Serology Examples: • Blood • Saliva • Sweat • Etc. What is serology? Serology is the study of serums.

  3. Ludwig Tessnow Case Tessnow’s clothes were tested. The results showed the stains were not dyes, but blood. As a result Ludwig was convicted of murder and executed in 1904. Germany 1901. Ludwig Tessnow was accused of murdering two children. He claimed red stains on his clothes were wood dyes. Paul Uhlenhuth – discovered how to test for blood and to distinguish between human and animal blood.

  4. Blood Typing In 1901 Karl Landsteiner discovered the human blood groups. The difference in blood groups are due to the presence or absence of certain protein molecules called antigens and antibodies. Landsteiner broke the groups into the familiar A, B, AB, and O.

  5. Blood Typing Today we use: Besides A, B, AB, and O there are over 100 blood factors that can be used to identify a person. Example: RH factor Until the 1990’s scientists used these factors to identify someone. DNA

  6. How much blood do we have? • You have about 10 pints of blood pumping through your body. • Plasma is the liquid portion of blood and it is 55% of the blood volume. • Red blood cells transport oxygen from the lungs and carbon dioxide to the lungs for removal. • Antigens on the surface of the RBC give them their blood characteristics. • White blood cells produce antibodies to disable and/or destroy invaders. • Platelets help to clot blood. The protein fribrin catches red blood cells.

  7. Secretors As a general rule, in the U.S. 80% of the population are classified as secretors. What is a secretor? A secretor is defined as a person who secretes their blood type antigens into body fluids and secretions like the saliva in your mouth, sweat, etc.

  8. Blood at the Crime Scene Hemastix will turn from yellow to dark green if blood is present. Is it blood? We use presumptive tests to answer this question. Hemastix – reacts with the hemoglobin in blood.

  9. Blood at the Crime Scene • Presumptive Tests (continued) • Kastle-Meyer Test • A drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. If the swab turns pink rapidly, it is said to test presumptive positive for blood.

  10. Blood at the Crime Scene Presumptive Tests (continued) Luminol – reacts with iron present in blood and a chemical reaction that leads to luminescence revealing the location of the blood. Picks up blood even if diluted up to 10,000 times.

  11. Blood at the Crime Scene From what species? Precipitin or Gel Diffusion – Blood from mummies 4,000 – 5,000 years old still give positive results! If it’s human blood, whose is it? • ABO Testing • DNA Fingerprinting

  12. Interpreting Blood Spatter • Blood spatter can tell us the following: • Direction blood droplet was moving • Where the blood droplet came from (area of origin) • Type of weapon used in the crime (number or blows) • Position of victim, suspects, and objects • Sequence of events

  13. Interpreting Blood Spatter The pointed part of the blood spatter give you the direction the blood was traveling at the point of impact. How to tell the direction that blood droplet was moving. Here is a picture of some blood spatter which hit a surface.

  14. Interpreting Blood Spatter • Working with multiple droplets can tell where the victim was located when the crime was committed.

  15. Angle of Impact • The angle of impact is useful in determining where blood spatter originated from. • To find the angle of impact: Sin (angle) = Width / Length

  16. Types of Blood Spatter Irregular spatter pattern indicate higher fall. Passive blood spatter is created by the force of gravity. Height determines diameter of blood spatter.

  17. Types of Blood Spatter • Projected blood spatter occurs when energy has been transferred to the blood source. The higher the velocity, the smaller the drops • Low, Medium & High Velocity • Falling blood drops • Gunshot wounds • Arterial Spurting • Cutting of an artery • Expiratory • Blood from mouth or nose

  18. Types of Blood Spatter • Contact or Transfer blood spatter occurs when an object with blood on it comes into contact with other objects. • Wipe • Swipe Surfaces and weapons can affect the blood spatter, therefore, testing of different variables is often done in a case.

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