Forensics - biological evidence
- Created by: Ashlee
- Created on: 30-04-15 14:15
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- Biological evidence
- visual identification
- texture/colour
- enhancing
- strong light source
- UV light
- laser
- fixed wavelength light source
- blood
- bright red - changes to brown/dark green
- plasma = hormones, waste, antibodies
- 55% of volume
- when fibrinogen removed it is serum
- platelets
- helps blood clot
- red blood cells
- haemoglobin carries oxygen
- contains blood type antigens
- white blood cells
- fight infection - part of immune system
- at scene
- presumptive tests
- Kastle Meyer Test (KM)
- ethanol, phenolphthalein and hydrogen peroxide on swab
- turns pink if positive
- ethanol, phenolphthalein and hydrogen peroxide on swab
- Hemastix
- Leucomalachite green (LMG)
- reagent of zinc, leucomalachite green, water and glacial acetic acid
- add to hydrogen peroxide
- if turns blue/green = positive
- add to hydrogen peroxide
- reagent of zinc, leucomalachite green, water and glacial acetic acid
- oxidation reactions
- false positives
- cheap and quick but further tests required
- Kastle Meyer Test (KM)
- presumptive tests
- semen
- pale and crusty
- suspension of spermatazoa cells
- slightly acidic
- rich in calcium, zinc, sodium and citric acid
- DNA in head of sperm
- presumptive tests
- lab based
- microscopy
- to see sperm cells
- acid phosphate test
- acid phosphatase secreted by prostate gland
- if semen present, when mixed with dye and sodium it will turn blue/green/orange/red (depending on dye)
- acid phosphatase secreted by prostate gland
- UV light
- flourescent
- saliva
- fluid excreted by salivary glands
- mucin - lubricates food
- salivary amylase - digestive starch
- can contain skin cells from inside mouth
- presumptive tests
- none at scene
- starch test
- add iodine if turns blue/black it is positive
- blood stain pattern analysis
- the interpretation of dispersion, shape, volume, number and relationship of bloodstains to reconstruct events
- active blood stains
- cast off
- movement
- body (artery/cough)
- gun shot/high velocity
- passive blood stains
- force of gravity
- formation of outer ring
- transfer bloodstains
- direct contact with contaminated objects
- objects leave silhuette/pattern
- footwear/fingermark
- contact/collapse phase - blood is pushed outwards into a rim
- angles important
- properties of blood
- viscosity = 3-4 mP.s-1
- surface tension = 0.058 N.m-1
- density = 1060 kg/m3
- visual identification
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