Serology. Serology. Study of bodily fluids: blood, semen, saliva, urine, vaginal secretions, and excrement DNA can also be collected from these samples. Blood. Plasma- fluid part of blood 90% water 10% salts, ions, proteins Red blood cells White blood cells platelets.
Serology Study of bodily fluids: blood, semen, saliva, urine, vaginal secretions, and excrement DNA can also be collected from these samples.
Blood • Plasma- fluid part of blood • 90% water • 10% salts, ions, proteins • Red blood cells • White blood cells • platelets
Karl Landsteiner • 1901 • Determined blood types (ABO and Rh) • Red blood cells have proteins (antigens) on the surface of the cell
Blood type A – has A antigens on surface • Blood type B- has B antigens on the surface • Blood type AB- has A and B antigens • Blood type O – neither A nor B antigens
Secretors • Some people have blood type antigens in other body fluids besides their blood
Collect info from location, distribution, & pattern of blood stains==> reconstruct events of the crime • Blood typing --> class evidence
Class Evidence • Can be associated with a general group • Cannot be associated with an individual source • Ex. Blood types
Individual evidence • Can be traced back to an individual source. • Ex. DNA sample from blood
Controls Positive control - known blood will cause the color to appear (solutions are working) Negative control - absence of blood- no appearance of color (shows there is no contamination)
More on presumptive tests • In most presumptive tests, the solution that is used for the test changes color when it comes in contact with blood. • The substances in the blood that cause the color change are • Hemoglobin • Peroxidase
Presumptive Tests for Blood (screening tests) A negative result means that the sample can be ruled out as being blood. • A positive results means that the sample is very likely blood. • Need to be confirmed by more specific tests
Presumptive Tests for Blood • Hematest tablets or Hemastix strips • Kastle-Meyer solution • Luminol
Hematest or Hemastix • Tablets or strips will turn blue/green in the presence of blood • This tablets or strips are available in some pharmacies
Kastle-Meyer color test • Aka: phenolphthalein test • Produces a bright pink color in the presence of blood. • False positives can be given by potatoes or horseradish, or shrimp cocktail
Luminol • Spray that makes blood residue glow a bluish color in total darkness. • Chemiluminesce = glow • Glow only lasts for a short time (second to minutes)
Is the blood human? • Use the precipitin test • To understand how this test works, you need to understand: • Serum • Antigens • Antibodies • Agglutinate • Antiserum
Confirmatory tests for blood • Takayama & Teichmann tests • When the right chemical solution is added to a bloodstain, crystals will form if the stain really is blood. • Crystals are visible under a microscope
Precipitin test – shows if blood is human or animal • Serum -A liquid that separates from whole blood • Antibodies- proteins produced by the body’s immune system that target bacteria, viruses, poisons (anything foreign)
Antigens- any foreign substance that causes an immune response in the body • (production of antibodies) • Agglutination- clumping of blood • Anti-serum – serum from humans or other animals that contain antibodies to a specific antigen
How is anti-serum produced for blood tests? • Ex. Human blood is injected into a rabbit. • The human blood is foreign to the rabbit, so the rabbit produces antibodies against the human blood. • Serum from the rabbit is collected. The serum contains antibodies to human blood.
If the serum is applied to an unknown sample of blood, the antibodies in the serum will bind to the blood if the unknown is human blood. • The binding of the antibody to the blood causes clumping of the blood cells • The clumping (agglutination) is very visible.
Why test blood when DNA is a more precise form of testing? DNA testing slow DNA testing much more expensive
History • Karl Landsteiner- Austrian immunologist and pathologist • 1901- showed blood types to be A, B, AB, and O
Probability of having a blood type • What is the chance of being B +? • B 10% = 1/10 • Rh += 85% = 85/100 • 1/10 X 85/100 =85/1000
Packaging blood from a crime scene • Blood must NOT be put into an airtight container • Any moisture in the container will lead to mold and mildew forming.
Rh factor • There is another protein (Rh) found on the surface of blood cells. • Also known as D antigen • 85% of the population is + for Rh. • If you have this protein you are +. • If you do not have this protein, you are -.
Questions to ask about fluids at a crime scene • 1. Are the stains blood, semen, saliva, or something else? • 2. Are the stains from a human or another animal? • 3. Who or what is the source of the stain?4. How, why, and when did they get deposited on items at the scene?
Whose blood is it? • Human blood has about 100 different antigens. • Only test for a few. • More than a dozen blood typing systems • The most common is the ABO system.
Blood Spatter Evidence • Angle of impact • Gushing pattern (arterial spurts) • Back spatter • Cast-off pattern • Contact stain • Direction of flight • Drawback effect • Drip pattern
HVIS= high velocity impact spatter • MVIS • LVIS • Misting-fine spray • Parent drop – has satellite spatters
Area of convergence • Area of origin • Spine • Swipe pattern • Void- area w/o blood stain