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Forensic Serology Ch. 12

Forensic Serology Ch. 12. Blood Baby...cute. Nature of Blood. The word ‘blood’ refers to a highly complex mixture of cells, enzymes, proteins, and inorganic substances. http://www.youtube.com/watch?v=qX7Fd_QNXYs. Karl Landsteiner. 1901 A, B, O system of blood classification

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Forensic Serology Ch. 12

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  1. Forensic Serology Ch. 12

  2. Blood Baby...cute

  3. Nature of Blood • The word ‘blood’ refers to a highly complex mixture of cells, enzymes, proteins, and inorganic substances. • http://www.youtube.com/watch?v=qX7Fd_QNXYs

  4. Karl Landsteiner • 1901 • A, B, O system of blood classification • Over 100 blood factors but this, most important • Nobel Prize for the find! • Best evidence to link type to an individual or eliminate an individual • Comparative, identifiable evidence

  5. PLASMA, The fluid portion of blood is composed principally of water.

  6. Red blood cells (erythrocytes), white blood cells (leukocytes), and platelets are the solid materials suspended in plasma.

  7. Antigens, usually proteins, are located on the surface of • red blood cells and are responsible for blood-type characteristics.

  8. Blood Typing • More than 15 blood antigen systems have been identified, but the A-B-O and Rh systems are the most important. • An individual that is type A has A antigens on his/her red blood cells, type B has B antigens, AB has both A and B antigens, and type O has neither A nor B antigens.

  9. Rh factor is determined by the presence of another antigen, the D antigen. • People having the D antigen are Rh positive; those not having the antigen are Rh negative.

  10. For every antigen there is a specific antibody that will react with it to form clumps known as agglutination. • Thus, if serum containing anti-B is added to red blood cells carrying B antigen, they will immediately react.

  11. Ratios of Blood Types • O+ 1 in 3 persons • O- 1 in 15 persons • A+ 1 in 3 persons • A- 1 in 16 persons • B+ 1 in 12 persons • B- 1 in 67 persons • AB+ 1 in 29 persons • AB- 1 in 167 persons

  12. Serology • The term serology is used to describe a broad scope of laboratory tests that use specific antigen and serum antibody reactions.

  13. The identity of each of the four A-B-O blood groups can be established by testing the blood with anti-A and anti-B sera. • The concept of specific antigen-antibody reactions has been applied to immunoassay techniques for the detection of drugs of abuse in blood and urine.

  14. Immunoassay • A number of immunological assay techniques are commercially available for detecting drugs through antigen-antibody reaction. • In a typical EMIT analysis, antibodies that will bind to a specific drug are added to the subject’s urine. • Other immunoassay procedures are also available, such as radioimmunoassay (RIA) which uses drugs labeled with radioactive tags.

  15. One such technique, the enzyme-multiplied immunoassay technique (EMIT), is used by toxicologists because of its speed and high sensitivity for detecting drugs in urine.

  16. In the EMIT assay, a drug that may be present in a urine specimen will compete with added labeled drug for a limited number of antibody binding sites. The labeled drugs are indicated by an asterisk. Once the competition for antibody sites is completed, the number of remaining unbound labeled drug is proportional to the drug’s concentration in urine.

  17. Antigen-Antibody Reaction • When an animal, such as a rabbit or mouse, is injected with an antigen its body will produce a series of different antibodies, all of which are designed to attack some particular site on the antigen of interest. • This collection of antibodies is known as polyclonal antibodies.

  18. Alternately, a more uniform and specific collection of antibodies designed to combine with a single antigen site can be manufactured; monoclonals.

  19. Stimulating production of drug antibodies.

  20. Steps required to produce monoclonal antibodies.

  21. The criminalist answers the following questions when examining dried blood: • (1) Is it blood? • (2) From what species did the blood originate? • (3) If the blood is of human origin, how closely can it be associated to a particular individual?

  22. The determination of blood is best made by means of a preliminary color test.

  23. Wet blood has more value than dried blood because more tests can be run. • For example, alcohol and drug content can be determined from wet blood only. Blood begins to dry after 3-5 minutes of exposure to air. As it dries, it changes color towards brown and black.

  24. Blood at the crime scene can be in the form of pools, drops, smears, or crusts. • Pools of blood obviously have more evidentiary value in obtaining a wet sample.

  25. Drops of blood tell the height and angle from which the blood fell. The forensic science of blood spatter analysis says that blood which fell perpendicular to the floor from a distance of 0-2 feet would make a circular drop with slightly frayed edges.

  26. Drops from a higher distance would have more pronounced tendrils fraying off the edges (a sunburst pattern).

  27. A blood smear on the wall or floor tells the direction of force of the blow.  • The direction of force is always in the direction towards the tail, or smaller end, of the smear, or splatter. In other words, the largest area of the smear is the point of origin (a wave cast-off pattern). • Blood crusts need to be tested with crystalline methods to make sure it's blood.

  28. Refrigerated red blood cells have a shelf life of about 42 days, and the serum containing white blood cells can be refrigerated up to a year.  • DNA can be extracted from blood (if white blood cells are present), and also from sperm, bone marrow, tooth pulp, and hair roots. • Blood is used in DNA testing, as per the following steps:

  29. 1. Blood samples are collected from the victim, defendant, and crime scene2. White blood cells are separated from red blood cells3. DNA is extracted from the nuclei of white blood cells

  30. 4. A restrictive enzyme is used to cut fragments of the DNA 5. DNA fragments are put into a bed of gel with electrodes 6. Electric current sorts DNA fragments by length7. An absorbent blotter soaks up the imprint; radioactively treated, and an X-ray photograph (called an autoradiograph) is produced 

  31. The Tests • A positive result from the Kastle-Meyer color test is highly indicative of blood. • Hemoglobin causes a deep pink color. • Alternatively, the luminol test is used to search out trace amounts of blood located at crime scenes. • Produces light (luminescence) in a darkened area.

  32. Microcrystalline tests, such as the Takayama and Teichmann tests, depend on the addition of specific chemicals to the blood so that characteristic crystals will be formed. • Precipitin test • Gel Diffusion

  33. The precipitin test

  34. Gel Diffusion

  35. A-B-O vs DNA • Prior to DNA typing, bloodstains were linked to a source by A-B-O typing and the characterization of polymorphic blood enzymes and proteins. • DNA analysis has allowed forensic scientists to associate blood and semen stains to a single individual.

  36. Stain Patterns of Blood • The crime scene investigator must remember that the location, distribution, and appearance of bloodstains and spatters are useful for interpreting and reconstructing the events that produced the bleeding. • Surface texture and the stain’s shape, size, and location must be considered when determining the direction, dropping distance, and angle of impact of a bloodstain.

  37. Blood stain analysis started with the French criminalist, Alexandre Lacassagne

  38. Stain Patterns of Blood • Surface texture is of paramount importance. In general, the harder and less porous the surface, the less spatter results.

  39. The direction of travel of blood striking an object may be determined because the pointed end of a bloodstain always faces its direction of travel.

  40. The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion. At right angles the blood drop is circular, as the angle decreases, the stain becomes elongated.

  41. The origin of a blood spatter in a two-dimensions can be established by drawing straight lines through the long axis of several bloodstains. • The intersection or point of convergence of the lines represents the origin point.

  42. Illustration of stain convergence on a two-dimensional plane. Convergence represents the point from which the stains emanated. Courtesy Judith Bunker, J. L. Bunker & Assoc., Ocoee, FL

  43. Categories of Blood Stains Passive Transfer Projected

  44. Transfer Bloodstains • A transfer bloodstain is created when a wet, bloody surface comes in contact with a secondary surface. • A recognizable image of all or a portion of the original surface may be observed in the pattern, as in the case of a bloody hand or footwear.

  45. Passive Bloodstains • Passive bloodstains are drops created or formed by the force of gravity acting alone.

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