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WHAT IS IT?

WHAT IS IT?

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WHAT IS IT?

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  1. WHAT IS IT? Forensic Serology Serology - is the scientific study of blood serum. • Purposes: Medical or Forensic • Blood samples can change the entire case • 1930, Karl Landsteiner received a Noble Prize award for his research in serology. He introduced to the scientific world that all human blood can be grouped into 4 types known as O, A, B, AB.

  2. Forensic Serology Serological tests may be performed for diagnostic purposes when an infection is suspected, in rheumatic illnesses, and in many other situations, such as checking an individual's blood type Diagnostic ID of antibodies in the serum. • Antibodies are formed in response to an infection (against a given microorganism) • Against other foreign proteins (in response, for example, to a mismatched blood transfusion) • One's own proteins (in instances of autoimmunedisease).

  3. Forensic Serology • Serology techniques vary depending on the antibodies being studied. Some are: ELISA, agglutination, precipitation, complement-fixation, and fluorescent antibodies. • Serological tests are not limited to blood serum, but can also be performed on other bodily fluids such as semen & saliva, which have similar properties to serum. • Serological tests may also be used forensically, generally to link a perpetrator to a piece of evidence (e.g., linking a rapist to a semen sample).

  4. Forensic Serology • Wet Blood vs. Dried Blood • Blood found in different forms • Refrigerated red blood cells and serum from white blood cells • Where DNA can be taken from • Blood pattern analysis helps in the reconstruction of many crime scenes The Crime Sceneand Blood

  5. Forensics of Blood The criminalist needs to answer the following questions when examining dried blood: • Is it blood? • From what species did the blood originate? • If the blood is of human origin, how closely can it be associated to a particular individual? The determination of blood is best made by means of a preliminary color test.

  6. Blood (HEMO) • Blood: water, white blood cells(leukocytes), red blood cells (erythrocytes), various platelets(last component of blood), various proteins, plasma. • Red blood cell : RBCs, Carry oxygen to organs of the body, O2. • White blood cells: WBCs, part of the Immune system, protects your body from infection and diseases

  7. Blood (HEMO) • The cellular fraction of blood contains red blood cells (erythrocytes) and white blood cells (leucocytes) • White blood cells (WBC) are • the source of DNA for DNA • typing analysis • Red blood cells (RBC) do not contain any nuclear DNA RBC WBC

  8. Plasma cells • Plasma: primary component (55%) in blood, it has two component: • Serum- yellow liquid, contains specific antibody • Clotting Proteins

  9. Blood and Body Fluid Individuality: Traditional Approaches 1. The Classical or Conventional Genetic Markers: • blood groups • isoenzymes • plasma (serum) proteins • hemoglobin variants • HLA • The first blood group markers were ABO, discovered in 1901 by Karl Landsteiner

  10. Blood and Body Fluid Individuality: Traditional Approaches • ABO markers were first applied to criminal cases involving bloodstains by Dr. Leon Lattes of Italy in 1913 • Isoenzymes are enzymes which occur in multiple molecular forms, reflecting differences in the gene that code for the enzyme • Similarly, there are common variants of the protein hemoglobin

  11. Blood and Body Fluid Individuality: Traditional Approaches 2. How Does Typing Genetic Markers Help “Individualize” a Biological Specimen? • A gene is a region of DNA that codes for a particular protein or enzyme • Because chromosomes are paired (maternal and paternal), and there is one gene on each chromosome, the genes are paired • A gene locus is the location on a chromosome where a particular trait is determined

  12. Blood and Body Fluid Individuality: Traditional Approaches • The genes making up a pair at a given locus are called alleles • The alleles may be the same (homozygous) or different (heterozygous) • Population genetics looks at how often alleles found at a given locus occur in a population

  13. Blood and Body Fluid Individuality: Traditional Approaches • A portion of a large population is sampled and tested to determine the frequency of a particular allele • Statistics are used to estimate the frequency of an allele in the entire population

  14. Antibodies and Antigens Antibody: Proteins that destroy or inactivate a specific antigen and are found in serum. Antigen: Substances that stimulates the proteins to produce antibodies against it.

  15. A-B-O vs DNA • Prior to the advent of DNA typing, bloodstains were linked to a source by A-B-O typing and the characterization of polymorphic blood enzymes and proteins. • This approach has now been supplanted by the newer DNA technology. • DNA analysis has allowed forensic scientists to associate blood and semen stains to a single individual.

  16. Preserving Evidence at the Crime Scene Forensic Serology • Blood evidence results if prepared and collected right • Communication from beginning of crime scene to court • Videotaping Blood Evidence • What Type of Film to use and at medium range • Chain of Custody

  17. Forensic Serology • A term which describes laboratory tests which employ a specific antigen/antibody reactions. The science dealing with serums and especially their reactions and properties. • It includes blood splatter patterns that leads to crime-scene analysis and eventually to a criminal. • Every species has a unique type of blood.

  18. Forensic Identification of Blood Categories of identification tests: • Presumptive or preliminary test • Used for screening specimens that might contain the substance or material of interest • Both false positive and false negative results may be obtained • Confirmatory test • Are tests which are entirely specific for the substance or material for which it is intended • A positive confirmatory test is interpreted as an unequivocal demonstration that the specimen contains the substance or material

  19. Forensic Identification of Blood Presumptive Tests for Blood: • Presumptive blood tests are used to screen evidence for the possible presence of blood • Most are color tests and are based on the peroxidase-like activity of hemoglobin • Peroxidase catalyzes the following reaction • Reduced Dye + peroxide --> Oxidized dye + water • The presence of hemoglobin catalyzes the reaction, forming a colored dye product • Positive presumptive tests do not prove that blood is present

  20. Forensic Identification of Blood Confirmatory Tests for Blood: • Older tests included crystal tests such as the Teichmann and Takayama tests • Current immunological tests use antibodies specific for human hemoglobin, thus combining the confirmatory test for blood with a human species test • The crystal tests and the immunological tests are known as direct confirmatory tests

  21. Species Determination Tests must be done on blood specimens to determine the species of origin • Species origin tests are done using immunological methods which involve the interaction of antigens and antibodies • Hemoglobin from human red blood cells can be used as the antigen to produce anti-human hemoglobin serum • Specific antiserum can be used to test for the presence of antigens in unknown specimens

  22. Species Determination • Common immunological species tests include the Ouchterlony method • Extracts of the bloodstain to be analyzed are tested with specific antisera • If the bloodstain contains the antigens corresponding to the specificity of the antiserum, a visible precipitate (precipitin) is obtained

  23. Forensic Nature of Blood Stains Blood is the most common and most important evidence in the world of criminal justice. http://projects.nfstc.org/gallery/main.php?g2_itemId=3857

  24. General Bloodstain Features • Bloodstain patterns deposited on floors, walls, bedding, and other relevant objects can provide valuable insights into events that occurred during the commission of a violent crime. • The crime scene investigator must remember that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding.

  25. General Bloodstain Features The information one can uncover as a result of bloodstain pattern interpretation includes: • The direction from which blood originated • The angle at which a blood droplet struck a surface • The location or position of a victim at the time a bloody wound was inflicted • The movement of a bleeding individual at the crime scene • The approximate number of blows that struck a bleeding victim • The approximate location of an individual delivering blows that produced a bloodstain pattern

  26. The Tests • A positive result from the KASTLE-MEYER color test is highly indicative of blood. • A presumed blood sample is first collected with a swab. • A drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxideis applied to the swab. • Hemoglobin causes a deep pink color. If the swab turns pink rapidly, it is said to test presumptive positive for blood. • Waiting for periods over 30 seconds will result in most swabs turning pink naturally as they oxidize on their own in the air.

  27. The Tests • The LUMINOL TEST is used to search out trace amounts of blood located at crime scenes. • Produces light (luminescence) in a darkened area. To exhibit its luminescence, the luminol must first be activated with an oxidant (H2O2) . Usually, a solution of hydrogen peroxide (H2O2) and a hydroxide (OH-) salt in water is used as the activator. In the presence of a catalyst such as an iron compound (Heme-in blood), peroxide is decomposed to form oxygen and water: 2 H2O2 → O2 + 2 H2O • In the forensic detection of blood, the catalyst is the iron present in hemoglobin. Enzymes in a variety of biological systems may also catalyze the decomposition of hydrogen peroxide. • BlueStar™ TEST- Comm. Test avail. – doesn’t need total darkness to observe in the field

  28. The Tests • Precipitin Test – simple test to determine if blood is of human or animal origin. (When animals are injected with human blood, antibodies form reacting with the human blood forming a precipitin band. • 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. It is a less sensitive test for blood ID. • Once it has been determined that the bloodstain is of human origin, an effort must be made to associate or dissociate the stain with a particular individual.

  29. Blood Stain Pattern Analysis • What mechanism creates stains • What direction a droplet of blood was traveling • Type of object used in attack • Position of victim, suspect, and objects • Combination of physics, hydraulics, and common sense • Helps to reconstruct crime scene and identify criminals • Draws from the sciences of biology, chemistry, math, and physics

  30. Blood Spatter • Blood Spatter is called Bloodstain Pattern Interpretation. • It involves reconstructing the events that must have happened to produce the bleeding. • It is not something that most law enforcement officials can do--it usually requires a specialist.

  31. Blood Spatter Herbert L. MacDonell published a study in 1971; gave tips to investigators: • To determine the impact angle of blood on a flat surface by measuring the degree of circular distortion of the stain. The more the angle decreases, the more the stain is less circular and more oblong. • Surface texture is one of the key components in determining spatter type, it means that the harder the surface is, the less spatter will result. • When a droplet of blood hits a surface which is hard as well as smooth, the blood usually breaks apart upon impact. This in turn causes smaller droplets. These droplets will continue to move in the same direction as the original droplet.

  32. Effects of Surface Texture • 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. • Surface texture is of paramount importance. In general, the harder and less porous the surface, the less spatter results.

  33. Directionality and Angle of Impact • The direction of travel of blood striking an object may be discerned because the pointed end of a bloodstain always faces its direction of travel. • 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. • Mathematically, the angle of impact can be calculated by the equation: Sin A = Width of blood stain Length of blood stain

  34. Impact Bloodstain Spatter Patterns • Impact spatter occurs when an object impacts a source of blood. • Forward spatter is projected outward and away from the source. • Back spatter, sometimes called blow-back spatter, is projected backward from the source,

  35. Classifying Impact Spatter Using droplet size to classify impact patterns by velocity gives investigators insight into the general nature of a crime but cannot illuminate the specific events that produced the spatter pattern. • Low Velocity Spatter- drops with diameters of 3 mm or more normally produced by minimal force at a speed of less than 5 ft/sec. • Medium Velocity Spatter- drops with diameters from 1-3 mm at a speed of 5 to 25 ft/sec. • High Velocity Spatter- drops with diameters of less than 1mm at a speed of 100 ft/sec or faster.

  36. 1. Determination of Angle of blood • The drop on the right fell 42 inches at an angle of 60-degrees on toward smooth cardboard, while the drop on the left fell the same 42 inches and on to the same surface, but at a 10-degree angle. Flight Characteristics and Stain Patterns of Human Blood, Herbert L. MacDonnell (Washington DC: USGPO,1971), pp. 44,49

  37. Blood Spatter • The blood drop at the right struck a plastic wall tile falling again from 42 inches. On the left, the drop fell from the same distance on to a piece of heavy, unusual textured wallpaper. Flight Characteristics and Stain Patterns of Human Blood, Herbert L. MacDonnell (Washington DC: USGPO,1971), pp. 36,37

  38. Blood Spatter • This drop of blood was tested traveling 4ft/sec., on to a hard cardboard surface. It was traveling from right to left at an angle of 56-degrees. Although not clear in the example, MacDonnell's test showed the smaller drops aimed toward the large one. Flight Characteristics and Stain Patterns of Human Blood, Herbert L. MacDonnell (Washington DC: USGPO, 1971), pg. 39

  39. Area of Convergence • The Area of Convergenceis the point on a two-dimensional plane from which the drops in an impact pattern originated. • This can be established by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails.

  40. Area of Origin • The Area of Originof an impact bloodstain pattern is the area in a three-dimensional space from which the blood was projected. • This will show the position of the victim or suspect in space when the stain-producing event took place. • The string method is commonly used at a crime scene to approximate the position of the area of origin using found angles of impact of individual stains in the pattern.

  41. Gunshot Spatter • Gunshot spatter is characterized by fine forward spatter from an exit wound and back spatter from an entrance wound. However, the gunshot produces only back spatter if the bullet does not exit the body. • Depending upon the distance from the victim that the gun was discharged, some back spatter may strike the gunman and enter the gun muzzle. This is called the drawback effect.

  42. Cast-off Spatter • A Cast-offpattern is created when a blood-covered object flings blood in an arc onto a nearby surface. • This kind of pattern commonly produced by a bloody fist or weapon between delivering blows. • The features of the cast-off pattern are affected by the size of the object, the amount of blood, and the direction the object was moving. • By counting and pairing forward/backward patterns, one may determine the minimum number of blows delivered.

  43. Arterial Spray Spatter • Arterial sprayspatter is created when a victim suffers an injury to a main artery or the heart, and the pressure of the continuing pumping of blood causes blood to spurt out of the injured area. • The site of the initial injury to the artery can be found where the pattern begins with the biggest spurt. The trail away from this point shows the victim’s movement. • The oxygenated blood spurting from the artery tends to be a brighter red color than blood expelled from impact wounds.

  44. Expirated Blood Patterns • An Expirated Blood Patternis created by blood that is expelled from the mouth or nose from an internal injury. • The presence of bubbles of oxygen in the drying drops or a lighter color as a result of dilution by saliva can differentiate a pattern created by expirated blood. • The presence of expirated blood gives an important clue as to the injuries suffered and the events that took place at a crime scene.

  45. Void Patterns • A void is created when an object blocks the deposition of blood spatter onto a target surface or object and the spatter is deposited onto the object or person instead. • The blank space on the surface or object may give a clue as to the size and shape of the missing object or person. • Voids may be applicable for establishing the body position of the victim or assailant at the time of the incident.

  46. Contact/Transfer Patterns • A Contact or Transfer Patternis created when an object with blood on it touches one that does not have blood on it. • Simple transfer patterns are produced when the object makes contact with the surface and is removed without any movement of the object.

  47. Contact/Transfer Patterns • The size and general shape of the object may be seen in a simple transfer. • Other transfers may be caused by movement of the bloody object across a surface.

  48. Flows • Flow patterns are made by drops or large amounts of blood flowing by the pull of gravity. • “Active” flows are formed by blood coming from an actively bleeding wound. • “Passive” flows originate with blood deposited on a surface such as an arterial spurt.

  49. Flows • The flow direction may show movements of objects or bodies while the flow was still in progress or after the blood dried. • Interruption of a flow pattern may indicate the sequence and passage of time between the flow and its interruption.