Chapter 10                                                                                                           3/30/...
Chapter 10                                                                                                                ...
Chapter 10                                                                                                                ...
Chapter 10                                                                                                         3/30/12...
Chapter 10                                                                                                                ...
Chapter 10                                                  3/30/12                                               Secretor...
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CHapter 11 Notes - Blood Analysis

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CHapter 11 Notes - Blood Analysis

  1. 1. Chapter 10 3/30/12 Chapter 11 Notes! Serology! Blood Evidence! Serology is the examination and analysis of body fluids.   Analyzes body fluids including saliva, semen, urine, and blood   Until the use of DNA, serology was one of the most important forensic tools Blood : The Basics! History of Blood Typing! 2 parts of blood: Karl Landsteiner (circa 1900)   Discovered 4 different types of human   Plasma(fluid = blood 55%).   based on the presence or absence of specific antigens found on the surface of   Cells (45%) the red blood cells. Erythrocytes - Landsteiner and Weiner (1940) red blood cells.   Discovered the Rh factor by studying the Serum is the liquid Leukocytes - blood of the Rhesus monkey that separates from white blood   85% of Caucasians, 94%of Black Americans, and 99%of all Asians are Rh the blood when a cells positive. clot is formed. Thrombocytes - Important Terms! Important Terms! Antigen—a substance that can stimulate the body to ABO blood groups— make antibodies. Certain based on having A, B, antigens (proteins) found in both, or no antigens the plasma of the red blood on red blood cells cell’s membrane account for Rh factor—may be blood type. present on red blood Antibody—a substance that cells; positive if reacts with an antigen present and negative if notKendall/HUnt 1
  2. 2. Chapter 10 3/30/12 Important Terms! Unknown Stain at a Scene! Agglutination—clumping of red Questions to blood cells; will result if blood types be answered: with different antigens are   Is it blood?   Is it human blood?   Whose is it?   Determine blood type, alcohol content, drugs present Some stains obvious, others I googled “blood type   Determine the method(s) in could be something agglutination” and this was else, like red wine the 1st picture! WTF??!?!! which blood may have been deposited Blood Determination! Latent Blood Determination! Presumptive test: used to initially confirm a stain is blood. Can be a false positive; need a confirmation test Luminol test Kastle-Meyer color test—a reaction with blood to mixture of phenolphthalein and produce light hydrogen peroxide; the • Glows in contact with blood hemoglobin will cause the formation of a deep pink color if • Sometimes UV helps to blood is present visualize Hematest tablet—reacts with the • Many false positives, heme group in blood, causing a including bleach blue-green color Human vs. Animal Blood! Human Blood Typing! Blood Groups 2 main ways to tell if blood is human: Type Antigen Antibody Can Give Can Get Blood To Blood From   Microscopic observation A A B A, AB O, A   Precipitin test •  Animal serum with human antibodies is Animal used B B A B, AB O, B Human •  Combine animal serum with unknown blood sample Neither A AB A and B nor B AB A, B, O, AB •  Antiserum will react with human proteins. This test is very sensitive and requires only a small amount of blood. O Neither A A and B A, B, O, AB O nor BKendall/HUnt 2
  3. 3. Chapter 10 3/30/12 Blood Types in US! Blood Pattern Reconstruction! Blood Type Frequency in US Population Scene Pattern Lab Results O+ 37.4% Reconstruction Reconstruction A+ 35.7% 1. Stain condition 1. Genetic marker typing B+ 8.5% 2. Pattern 2. Age determination O- 6.6% 3. Distribution 3. Source determination A- 6.3% 4. Location 4. Race determination AB+ 3.4% B- 1.5% 5. Directionality 5. Sex determination AB- .6% Blood Spatter! Blood Droplet Characteristics! Blood Spatter Analysis: A field of forensic A blood droplet remains spherical investigation that deals with the physical properties in space until it collides with a of blood and the patterns produced under different surface. conditions as a result of various forces being Once a blood droplet impacts a surface, a bloodstain is formed. applied to the blood. Blood, as a fluid, follows the laws of PHYSICS. Droplets falling from the same Dear God, did height, hitting the same surface at she just say PHYSICS!!?!?! the same angle, will produce stains with the same basic shape. Blood Droplet Volume! Conditions Affecting Shape of Blood Droplet! A droplet contains approximately 0.05 cc of 1.  Size of the droplet fluid. 2.  Angle of impact Is not the same for all blood droplets, but is generally from 0.03 cc to 0.15 cc 3.  Height 4.  Velocity at which the blood droplet left its origin Is directly dependent upon the surface or orifice from which it originates 5.  Texture of the target surface •  On clean glass or plastic—droplet will have smooth The impact area is called the target. outside edges •  On a rough surface—will produce scalloping on the edgesKendall/HUnt 3
  4. 4. Chapter 10 3/30/12 What Spatter Analysis Can Show! Bloodstain Terminology!   The distance between the target surface and the Angle of impact—angle at which origin of the blood blood strikes a target surface   The point(s) of origin of the blood   Movement and direction of a person or an object Bloodstain transfer—when a   The number of blows, shots, etc., causing the bloody object comes into contact bloodshed and/or the dispersal of blood with a surface and leaves a   Type and direction of impact that produced the patterned blood image on the bloodshed surface   The position of the victim and/or object during bloodshed Cast-off—blood that is thrown from   Movement of the victim and/or object after an object in motion bloodshed Bloodstain Terminology! Bloodstain Terminology! Backspatter Contact stain—bloodstains caused by contact between a wet blood- blood that is bearing surface and a second directed back surface that may or may not have toward the source of blood on it energy Swipe—wet blood is transferred to a surface that did not have blood on it Forward spatter blood that is Wipe—a non-blood-bearing object moves through a wet bloodstain, directed away from altering the appearance of the original the source of energy stain Bloodstain Terminology! Bloodstain Terminology! Directionality—relates to the High velocity—greater than 25 direction a drop of blood travels in feet per second, usually 100 feet per second; gives a fine mist space from its point of origin appearance (gun) Terminal velocity—the greatest speed to which a free-falling drop of Medium velocity—5 to 25 feet blood can accelerate in air. It is per second (blunt force/stabbing) dependent upon the acceleration of gravity and the friction of the air Low velocity—5 feet per second against the blood—approximately or less (blood dripping) 25.1 feet/second.Kendall/HUnt 4
  5. 5. Chapter 10 3/30/12 Bloodstains Patterns! Bloodstains Patterns! Impact The shape of a blood drop:   The more acute the angle of impact, the more Round—if it falls straight down at a 90-degree elongated the stain. angle   90-degree angles are Elliptical—blood droplets elongate as the angle perfectly round drops; 80- decreases from 90 to 0 degrees degree angles take on a more elliptical shape.   At about 30 degrees the Impact angle = sin-1 (arcsin) width stain will begin to produce length a tail. The more acute the angle, the easier it is to determine the direction of travel. Bloodstains Patterns! Where did the blood come from?! Area of Intersection and Convergence   The harder and less porous The location of the blood source the surface, the less the can be determined by drawing blood drop will break apart. lines from the various blood droplets to the point where they   The softer and more porous intersect. the surface, the more the The area of convergence is the blood drop will break apart. point of origin; the spot where the “blow” occurred. It may be   The pointed end of the established at the scene by bloodstain faces the measurement of angles with the direction of travel. use of strings. Using cool strings or lasers! Blood Evidence! Class evidence for blood includes blood type. If you can determine the DNA, you will have individual evidence. Bloodstain patterns are considered circumstantial evidence in a courtroom. Experts can argue many Colored strings attached to the wall This is actually the use of lasers to reconstruct bullet trajectories, points, including direction of travel, above this bed at each blood drop but the idea is the same with height of the perpetrator, position of helps to determine the position of the victim on the bed. blood spatter. the victim, left/right hand, whether the body was moved, etc.Kendall/HUnt 5
  6. 6. Chapter 10 3/30/12 Secretors!   80% of the population are secretors. Their blood-type antigens are found in high concentration in their body fluids such as saliva, semen, vaginal secretions, and gastric juices.   Allows for blood typing when no blood is present – gives more class evidence.Kendall/HUnt 6

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