Forensic Serology Determination of type and characteristics of blood, blood testing, and blood stain examination

Blood Slightly basic fluid made of water, cells, enzymes, proteins,and inorganic substances Plasma – fluid portion, mostly water Serum – yellow and contains white blood cells (leucocytes), separates from blood when a clot forms –Used to determine freshness of blood, takes several minutes for blood to clot in air Red blood cells – solid materials –Used to determine blood type

Blood Typing On the surface of red blood cells are antigens, which give blood type characteristics Over 20 blood group systems –A B O and Rh (D antigen) most important For every antigen there is an antibody in the serum

Variation in Blood Types “O” is the most common among Indigenous people and Latin Americans “A” is common for European decent “B” for African American and certain Asians “AB” common among Japanese and Chinese

Percent with B

Percent with A

Percent with O

Where do red blood cells come from? Formed from stem cells in bone marrow of ribs, breastbone, pelvis, and vertebra –If all we had were bones, we could find out blood type from marrow

Blood as Evidence 1.Is it blood? 2.Is it animal or human blood? 3.If animal, what species? 4.If human, what type? 5.Whose blood is this?

Presumptive Tests Kastle-Meyer test uses phenolphthalein –It turns bright pink when it contacts hemoglobin in blood Precipitin test for determining animal vs. human Absorption-elution test to determine blood type (ABO)

Fluorescent Tests Luminol test can be used to reveal invisible blood –Glows in the dark Fluorescein reveals invisible blood –Thicker that luminol, so does not run when sprayed on walls

Animal Blood Types Dog Blood Types 8-12 canine blood groups are recognized Blood types among dogs are specified by the letters DEA, followed by some number(s) denoting which DEA system antigens are present on the red blood cells of the dog Canine Blood Type DEA 1.1 DEA 1.2 DEA 3 DEA 4 DEA 5 DEA 6 DEA 7 DEA 8

Cat Blood types Domestic cats have a two antigen blood group system which yields three possible blood types for a cat: A, B, or AB. Almost 99% of domestic short hair cats in the USA have type A blood. Other Animals There are eight recognized blood groups in the horse: A, C, D, K, P, Q, T, and U. Cattle blood groups include the A, B, C, F, J, L, M, S, and Z Two complex chimpanzee blood group systems, V-A-B- D and R-C-E-F systems

Other evidence Shape and pattern can reconstruct murder –Position and movement during crime Bloody prints Dried blood on suspects clothing can link to victim, scene and weapon

Crime Scene Blood Wet blood is more valuable than dried Blood begins to dry 3-5 minutes after exposure to air –As it dries it turns a brown/ black color

Find Blood at Scene in Several Forms Pools better for obtaining wet sample Drops tell height and angle from which it fell Smear tells the direction of force of a blow –Direction is always toward the tail of spatter; largest area is point of origin Crusts need to be tested to make sure it is blood