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