Pathology
INTRODUCTION:
Blood has always been considered class evidence in
forensic Science.
• Individualized blood evidence is possible in the near future.
NATURE OF BLOOD:
• Slightly alkaline fluid
• Circulates throughout our bodies, nourishing our cells, transporting oxygen and waste.
• Fluid portion of blood consists of plasma and serum .
• Non-fluid portion consists of red blood cells which
outnumber white cells by five hundred to one
• Blood is composed of:
o Water
o Cells
o Enzymes
o Proteins
o Other inorganic substances
RED BLOOD CELLS:
• Most prevalent blood cells in the human body.
• Deliver oxygen from the lungs to the body’s tissues.
• Forensic analyst search for smaller chemical substances
residing on their surfaces (ie. antigens), which also tend to
have important forensic implications.
SERUM:
• Characterized by its yellow hue, and contains white blood cells and platelets.
• Forensic analysts able to determine the freshness of a blood sample by examining serum (it clots several minutes after exposure to air).
• A centrifuge can be used to separate the clotted material from the serum portion.
• Serum contains antibodies , proteins floating in blood fluid, which have significant forensic implications.
SCREENING TESTS:
1. Luminol Test
o To reveal these traces with a light-producing chemical reaction between several chemicals (ie hydrogen peroxide) and hemoglobin,
an oxygen-carrying protein in the blood.Benzidine Test
2. Phenolphthalein( Kastle- Meyer’s) Test
o Phenolphthalein is colourless when it's reduced (has electrons), and pink when it's oxidized with hemoglobin (no electrons)
3. O-tolidine Test
o a test for the presence of hemoglobin in feces or urine. The O-toluidine can be in solution, in a tablet or impregnated onto absorbent paper. A
positive test is the development of a green to blue color.
4. Leucomalachite Green Test
• Blood is an important evidence in crime scene and must be carefully detected and collected.
• Blood screening is used generally to screen out the
suspects not involve and to provide a more solid evidence to determine the criminals.
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