Forensic Blood Analysis: Importance and Techniques

1. Chapter 6Serology Prof. J. T. Spencer Adjunct Prof. T. L. Meeks

2. Learning Goals and Objectives The study of blood, both of its biochemical composition and its physical fluid properties, can yield information of critical important to forensic investigations. In order to gain insights into how blood evidence can provide this valuable information…

3. Learning Goals and Objectives • How blood functions in our bodies and its various components • What is meant by presumptive and confirmatory tests • How blood can be detected and identified as human • How immunoassays work • What blood types are and how they work

4. Learning Goals and Objectives • The hereditary patterns of blood types • What is meant by blood pattern analysis • How events can be understood through blood pattern analysis • How other body fluids can be used in forensic science

5. Blood A hundred years ago, the legal world was desperately seeking some unique marker that could unambiguously tie a particular individual with a sample collected at a crime scene. • The best technique at the time for doing this, fingerprinting, had both its successes and serious limitations. • After a landmark discovery by Karl Landsteiner in 1901, however, attention turned to the analysis of blood

6. Blood • A complex mixture of cells, enzymes, proteins & inorganic substances • Fluid portion of blood is called the plasma (55% of blood content) • primarily water • Red cells (erythrocytes) • White cells (leukocytes) • Platelets (thrombocytes)

7. Blood Properties • Accounts for  about 8 % of total body weight. • 5 to 6 liters of blood for males. • 4 to 5 liters of blood for females. • A 40 percent blood volume loss, internally or/and externally, is required to produce irreversible shock (death). • A blood loss of 1.5 liters, internally or externally, is required to cause incapacitation.

8. Blood • Many Components: Human Red Blood Cells (in red), Platelets (yellow) and T-lymphocyte (light green) [also contains waste products, enzymes, etc.].

9. Red Blood Cells • Red blood cells (RBCs, erythrocytes), are the most abundant cells in the blood and give it its characteristic red color. Average of 5,000,000 RBCs per cubic microliter (mm3). RBCs account for 40 to 45 percent of the blood. The percentage of blood made up of RBCs is frequently measured and is called the hematocrit. The ratio of cells in normal blood is 600 RBCs for each white blood cell and 40 platelets. • There are several things about RBCs that make them unusual: • An RBC has a strange shape -- a biconcave disc that is round and flat, like a shallow bowl. • An RBC has no nucleus. The nucleus is extruded from the cell as it matures. • An RBC can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries. • An RBC contains hemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it.

10. Red Blood Cells • Transport oxygen from the lungs to the body tissues • Transport carbon dioxide from the tissues to the lungs • Red cells possess chemical structures on their surfaces called antigens or agglutinogens • impart blood type characteristics

11. White Blood Cells and Platelets • White blood cells (WBCs, leukocytes), are a part of the immune system and fight infection. WBCs circulate in the blood to be transported to an infection site. In a normal adult body there are 4,000 to 10,000 (average 7,000) WBCs per microliter (mm3) of blood. When the number of WBCs in your blood increases, it is a sign of an infection somewhere in your body. • Platelets (thrombocytes) help blood to clot by forming a platelet plug, blood clots (through coagulation factors), or other blood clotting mechanisms. There are approximately 150,000 to 400,000 platelets in each microliter of blood (average is 250,000).

12. Blood Clotting • Blood Clot Formation (blood cells, platelets, fibrin clot)

13. Plasma • Plasma is a clear, yellowish fluid (the color of straw). Plasma can sometimes appear milky after a very fatty meal or when people have a high level of lipids in their blood. • Plasma is 90-percent water. The rest is protein. • Blood contains hundreds of other chemical components beyond those described thus far including fibrinogen, salts, proteins, glycoproteins, carbohydrates, antibodies, hormones (e.g., insulin, testosterone, estrogen, adrenaline or epinephrine, etc.), albumin, and dissolved gases. The most common protein in our plasma is albumin, which is responsible for maintaining a proper fluid balance between our tissues and the rest of our bodies.

14. Blood Chemistry Hemoglobin (basic unit in red blood cells) is a protein containing heme groups. Proteins are amino acids linked together (peptide bond) to form long chains. Amino Acid

15. What is Serology? • A term which describes laboratory tests which employ a specific antigen and serum antibody reactions What is Immunology? • A term which deals with all aspects of the immune system – specific to the interactions between antibodies and antigens

16. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Blood origin (human or other source). • Blood Type. • Blood Spatter Analysis.

17. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Hemoglobin has peroxidase-like activity (enzymes that accelerate oxidation of organic compounds). • Benzidine Color Test - previously used but dropped due to carcinogenic reagents. • Kastle-Meyer Test - uses phenolphthalein. Blood+ phenolphthalein + H2O2 yields a deep pink color. Can give false positives (horseradish, some vegetables, potatoes, etc.)

18. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Luminol Test. Rx of luminol w/ blood produces a complex which can be seen by luminescence. • Very sensitive - up to a 3,000,000 dilution of blood can be seen. • Detects unseen samples and patterns. • Does not interfere with later DNA testing.

19. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Presumptive Test • An analysis that suggests blood could be present • Fast and relatively sensitive • Confirmatory Test • An experiment that can indicate the presence of blood with a high degree of certainty

20. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Blood origin (human or other source). • Precipitin Test - When animals are injected w/ human blood they form antibodies to the human blood. Can isolate human antiserum (antibodies to human blood). • Human antiserum will react with human blood. • Antiserum can (has) been made similarly for many other animals. • Works on old (dried for many years) and small samples of blood.

21. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Blood origin (human or other source). • Blood Type. • ABO and Rh testing. • Additional blood groupings • Enzyme presence (many possible enzymes can be determined that are genetically controlled).

22. Blood Types • Karl Landsteiner, 1900 Noted that when blood from different people is mixed it sometimes forms precipitate - deadly if mixed in body. Explored why. Blundell's blood transfusion apparatus, 19th century

23. Blood Type • Three types (alleles) of blood type gene • A, B, O • Each individual inherits one blood type gene from their mother & one from their father • 6 possible combinations (genotypes) • AA, BB, OO, AB, AO, and BO • Genotype determines blood type

24. Antibodies or Agglutinins • Proteins that are present in the serum • responsible for ensuring that the only blood cells that can survive in a person are cells of the correct blood type

25. Antibodies produced by the A alleles remove any red blood cells containing B antigens by clumping them together • Antibodies produced by the B alleles remove any red blood cells possessing A antigens

27. Type O Blood • Possessed by people whose genotype is OO • both parents passed on the O gene • have no antigens • these cells can be introduced into a person with Type A or Type B because these cells are not attacked by the antibodies these people possess • have both a & b antibodies • can only have other O type cells mixed with this blood

28. Type A • Possessed by people with genotype • AA • AO • A is dominant to O • Possesses antibody b • will destroy any Type B red cells • compatible with A or O red cells

29. Type B • Possessed by people with genotype • BB • BO • B is dominant to O • Possesses antibody a • will destroy any Type A red cells • compatible with B or O red cells

30. Type AB • Possessed by people with genotype • AB • A & B are co-dominant • Possesses no antibody • can have A, B, AB, or O cells added • Can’t be added to any other blood type without being destroyed by an antibody

33. Blood Typing • Blood typing is done by reacting whole blood with antibody A and antibody B

34. Blood Typing

35. Relative Frequency of Blood Types in Human Populations

36. Forensic Blood Analysis • Blood ID (“Is it blood”?). • Blood origin (human or other source). • Blood Type. • Blood Spatter Analysis.

37. Blood Spatter Analysis • Bloodstain Pattern Analysis:the examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin. • Bloodstain Pattern Analysiscan be used to: • Confirm or refute assumptions concerning events and their sequence: Position of victim (standing, sitting, lying). Evidence of a struggle. (blood smears, blood trails) • Confirm or refute statements made by principals in the case: Are stain patterns on a suspects clothing consistent with his reported actions? Are stain patterns on a victim or at a scene consistent with accounts given by witnesses or the suspect?

38. Bloodstains Passive Projected Transfer

39. Passive Bloodstains • Passive Bloodstains are drops created or formed solely by the force of gravity. • Can be subdivided into drops, drip patterns, pools, and clots.

40. Surface Bloodstains (Passive) • Bloodstains can occur on a variety of surfaces including clothing, carpeting, walls, etc. • The type of surface the blood strikes affects the nature of the observed splatter pattern. • Blood droplets that strike a hard smooth surface (e.g., glass) will have little distortion around the edges of the droplet. • Blood droplets that strike linoleum flooring will often show distortion (scalloping) around the edge of the blood droplets. • Blood droplets striking wood or concrete are distorted to a larger extent (e.g., spines and secondary splatter). Smooth Linoleum Concrete

41. Transfer Bloodstains • A transfer bloodstain is created when a wet, bloody surface comes in contact with another surface. • Occasionally, a recognizable image of the original surface may be observed in the pattern, such as a hand or shoe pattern. • Subdivided into Contact bleeding, Swipe or Smear, Wipe, and Smudge.

42. Bloodstains Dripped Spilled patterns created by same volume of blood, from same source to target distance Projected

43. Projected Bloodstains • Projected bloodstains are created when a blood source is subjected to an action greater than the force of gravity.  • The size, shape, and number of resulting stains will depend on the amount of force utilized to strike the blood source.

44. Projected Bloodstains - Types • Arterial Spurt / Gush - Bloodstain pattern from blood spurt under pressure from a cut artery. • Cast-off Stains - Blood released or thrown from a blood-soaked object in motion. • Impact Spatter - Blood stain patterns created when a blood source receives a blow or force resulting in the random dispersion of smaller drops of blood. Arterial Cast-Off

45. Projected Bloodstains - Impact • Low Velocity - Gravitational pull up to5 feet/sec.Relatively large stains4 mm and greater. • Medium Velocity - Force of 5 to 25 feet/sec.Stain size1 to 4 mm. • High Velocity - Force of 100 feet/sec. andgreater. Stain size1 mm and smaller (Mist like appearance). Low Medium High

46. Blood Spatter • DIRECTIONALITY OF BLOODSTAINS • When a droplet of blood strikes a surface perpendicular (90 degrees) the resulting bloodstain will be circular.   • Blood that strikes  a  surface at an angle  less than  90 degrees will be elongated or have a tear drop shape. • Directionality is usually obvious as the pointed end of the bloodstain ( tail ) will always point in the direction of travel.

47. IMPACT ANGLE DETERMINATION • ANGLE of IMPACTis the acute angle formed between the direction of the blood drop and the plane of the surface it strikes By utilizing trigonometric functions its possible to determine the impact angle for any given blood droplet. SIN θ = opp  (a)               hyp  (c)

48. Blood Spatter • SIN < = Width  (a) 1.5cm •               Length (c) 3.0cm

49. Blood Spatter • POINT OF CONVERGENCE AND ORIGIN DETERMINATION 2 Dimensional Analysis

50. Blood Spatter • POINT OF CONVERGENCE AND ORIGIN DETERMINATION 3 Dimensional Analysis