Examination of Bloodstains

Examination of Bloodstains

• Examination of bloodstains involves several steps, including physical, chemical, and serological examinations
• Physical examination focuses on aspects like color, which changes based on age and source
  • Fresh blood stains are bright red
  • 1-2 days old stains are reddish-brown
  • 2-3 days old stains are dull brown
  • Blood on leather immediately turns brown due to formation of metHb
  • Blood on glass remains red for several months
• Clotting usually occurs within 2-10 minutes of blood shedding, transforming soluble fibrinogen into insoluble fibrin
  • Blood from a dead body is partially coagulated because plasma lacks fibrinogen, gradually changing into fibrin
  • Clotting can be delayed due to factors like hemophilia, warfarin toxicity, and asphyxia
• Dryness depends on atmospheric conditions
  • Fresh blood stains are wet and may take 20-30 minutes to dry in Egypt's conditions

Solubility

• Fresh blood stains contain oxyHb, which dissolves in distilled water or normal saline
• Older stains contain metHb or hematin, dissolving in diluted acid or alkali
• Very old stains have hematoporphyrin, which dissolves in strong acid or alkali
• Blood in burns requires 5% HCl for dissolving

Shape

• Arterial blood stains are in jets or sprays
• Circular stains form if blood drops vertically onto a surface
• Pear-shaped stains indicate a wounded, moving person; the narrower end points towards the direction of movement

Preliminary (Macrochemical) Tests

• Good negative tests confirm if a substance is not blood
• These tests rely on the presence of protein and oxidase enzymes in blood
• The stain is prepared as a clear solution (if turbid, filtered)
• Tests for protein, ammonia, and foam (Ganttner's)

Tests based on oxidase enzyme

• Oxidases are also found in vegetable stains
• These tests (Guaiacum, Benzidine, Phenol phtalein, Kastle-Meyer's, O-Tolidine, Leucomalachite Green tests) only produce good negative results

Confirmatory Chemical Tests (Micro-chemical)

• These tests rely on the presence of hemoglobin in dried blood
• Teischmann's test (Haemin crystals) and Takayama's test (Haemochromogen crystals)
  • Reagents include NaCl (1 gm), NaBr (1 gm), NaI (1 gm), and acetic acid (100cc)
  • Crystals are brown and rhombic
  • Reaction is acidic
  • Crystals often appear single or in groups, forming "Chinese lettering"

Takayama's Test (Haemochromogen Crystals)

• Reagents include NaOH (1 part), pyridine (1 part), saturated glucose solution (1 part), and distilled water (7 parts)
• Crystals are pink and spindle-shaped
• Reaction is alkaline
• Crystals appear in groups, forming feather or rosette-like patterns

Microscopical Examination

• Confirmatory tests for bloodstains based on blood cells
• Used primarily for fresh blood samples
• Samples are stained with Leishman or Giemsa stains

Species Determination (Blood Cells)

• Mammalian blood cells (excluding camels) are circular, biconcave, and non-nucleated
• Camel blood cells are oval, biconvex, and non-nucleated
• Other non-mammalian blood cells (e.g., birds, reptiles) are oval, biconvex, and nucleated

Blood Cell Diameters

• Sheep/goat RBCs: 5.5 microns
• Horse/cat/ox/pig RBCs: 6 microns
• Human/rabbit/dog RBCs: 6.5 microns
• Elephant RBCs: 9.5 microns

Sex Determination (Neutrophils)

• About 3% of female neutrophils contain a Barr body (drumstick), a small nuclear mass attached to the nucleus by a thin filament

Toxicity (Lead)

• Lead toxicity interferes with pyrimidine-5-nucleotidase enzyme action
• Resultant RBCs show basophilic fragments or stippling in the blood film

Spectroscopic Examination

• Spectroscopic method verifies hemoglobin or its derivatives within stains
• Technique involves adjusting apparatus for distinct Fraunhofer lines; stain fluid is interposed between apparatus source.
• OxyHb exhibits two dark bands between lines D and E
• CarboxyHb displays bands similar to oxyHb but shifted to the right
• ReducedHb shows a single, broad, badly defined band between lines D and E
• MetHb displays four bands—one close to D-line, a second near E-line, two more in the C/D area and E/F area

Serological Examination (Precipitin Test)

• Injecting a specific protein (serum) into an animal creates antibodies within the animal's blood
• Antibodies react specifically with injected substance upon contact

Precipitin Test (Details)

• Rabbits or fowl are injected with human blood every 3rd day for 3-5 times
• Once killed, the animal's anti-serum is collected
• A suitable antiserum should react with the substance immediately at 1/1000 dilution

Blood Grouping

• Blood grouping helps determine if a bloodstain originated from a particular individual

This quiz covers the detailed examination of bloodstains, including physical, chemical, and serological aspects. It discusses the color changes in bloodstains over time, factors affecting clotting, and the role of environmental conditions in the drying process. Test your knowledge on these critical forensic elements!