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Forensic Serology Flipped Lesson #2
§ Is it blood?
§ From which species did the blood originate?
§ If the blood is human, how closely can it be associated with a particular individual?
The criminalist must answer these questions:
Is Blood Present?§ Chemical Reagent: Luminol: reacts with hemoglobin in blood
causing luminescence.
§ Produces a bluish glow in 5 seconds
§ Glow intensity increases with amount of blood.
Tests§ Kastle-Meyer color test: answers the
question is it blood?
§ Luminol test: determines the presence of trace amounts of blood
§ Precipitin Test: uses antisera normally derived from rabbits that have been injected with blood of a known animal to determine species origin
§ Secretor: an individual who secretes his or her blood-type antigen(s) in body fluids.Approximately 80 percent of the population are secretors
Secretors
Blood type & Probability
Using blood type to predict the probability of a particular blood type in a population:
What percentage of population would have blood type A+?
Type A = 42% of populationRh+ = 85% of population
1.Convert % to decimal: 42% = 0.42 85% = 0.852. Multiply decimals 0.42 x 0.85 = 0.3573. Convert to % by x by 100 = 35.7%
4. 36 out of 100 will be A+
Other proteins & Enzymes:Probability of uniqueness continues to increase with more proteinsM & N
Ex. MM = 30% MN = 48% NN = 22%
Calculate percentage with O-, MN: O = 43% = 0.43 Rh- = 15% = 0.15 MN = 48% = 0.48
0.43 x 0.15 x 0.48 = 0.031
0.031 = 3.1% or 3 in 100 people