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Species Origin

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  245

2026-08-01

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Species Origin

Tests that determine the species from which a blood sample originated fall into two general categories: diffusion reactions and electrophoretic methods. The most common diffusion reaction test, the Ouchterlony test, is based on an antibody–antigen reaction between human blood and human antiserum. Human antiserum is typically produced by injecting rabbits with human blood. The rabbit’s immune system, reacting to the foreign blood, produces antibodies to neutralize it. When the rabbit’s human-sensitized blood is drawn and the serum isolated, it can be used to detect human blood because it now has antibodies that will react specifically with human blood. Other antisera, for dogs, cats, and horses, for example, can be produced in a similar way. The Ouchterlony test is performed as follows. An agarose gel is poured into a small petri dish. A circular pattern of six wells is cut out of the gel with an additional well in the center. The antihuman serum is placed in the center well with a known human control placed in every other well. The sera and samples are allowed to diffuse. The human controls test positive (of course) with a diffusion line; if the unknown tests positive, the line extends between the adjoining known samples (see Figure 10.1). The Ouchterlony test is being supplanted by the Hematrace™ card, where a positive test is indicated by a color change. Electrophoresis methods are based on the diffusion of antibodies and antigens on an electrically charged gel-coated plate. The bloodstain extract and the human antiserum are placed in separate wells on opposite sides of the plate. When the plate is charged, a zone of precipitation forms at the juncture of the antibodies and anti gens; Figure 10.2 shows an electrophoresis device.