8 3 Forensic Characterization of Bloodstains Unit 8

8 -3 Forensic Characterization of Bloodstains Unit 8: Forensic Serology

Examining Blood • The criminalist must answer the following questions when examining dry blood: • Is it blood? • From what species did the blood originate? • If the blood is human, how closely can it be associated with a particular individual?

Is it blood? • The determination of blood is best made with the Kastle-Meyer color test. • A positive result from the Kastle-Meyer color test is highly indicative of blood.

Is it blood? • The luminal test is used to find trace amounts of blood at crime scenes.

From what species did the blood originate? • The precipitin test uses antisera normally derive from rabbits to have been injected with the blood of known animal to determine the species origin of the question blood stain.

Precipitin Test

Precipitin Test • Materials undergoing electrophoresis are forced to move across a gel-coated plate under the influence of an electrical potential.

Blood Serum • Antigens and antibodies can be induced to move toward one another under the influence of electrical field.

If the blood is human, how closely can it be associated with a particular individual? • Blood, determined to be human was originally characterized by A-B-O blood types. • DNA profiling is used to associate with a particular individual.