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FORENSICS CASE 12.05.05

FORENSICS CASE 12.05.05. Focus: To be able to explain how we collect evidence. FORENSIC EVIDENCE TYPES. 1./ Visual 2./ Microscopical 3./ Chemical 4./ Chromatographic. 5./Using databases 6./ Refractive index. THE FORENSIC PROCESS. Observe scene – How?. Collection of evidence – How?.

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FORENSICS CASE 12.05.05

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  1. FORENSICS CASE 12.05.05 Focus: To be able to explain how we collect evidence.

  2. FORENSIC EVIDENCE TYPES • 1./ Visual • 2./ Microscopical • 3./ Chemical • 4./ Chromatographic

  3. 5./Using databases • 6./ Refractive index

  4. THE FORENSIC PROCESS • Observe scene – How?

  5. Collection of evidence – How?

  6. COLLECTION OF EVIDENCE • We need to ensure that forensic evidence is not contaminated. • To ensure that the following process has to occur:- • 1./ Examine the incident scene (observe and record) • 2./ Collect samples (label and seal in bags)

  7. 3./Testing and analysing (Chemical tests, blood tests, etc) • 4./ Interpreting results (What facts are shown by results from tests, and what can be deduced.)

  8. 5./ Prepare the report (accurate, clear and concise) • 6./ Presenting evidence in court (Evidence indicates probability rather than proof.)

  9. Collecting evidence • Alcohol :- Breathing into a breathalyser, or taking samples of blood and urine and testing with potassium dichromate.

  10. Drugs – samples of powders are collected in plastic bags and vials. Plant material is placed in paper bags.

  11. Explosives – Residue collected from site of explosions. Smells noted and accessories like blasting caps collected.

  12. Arson – Collecting samples of porous materials from near source of fire. (eg:- Under the settee.)

  13. Ballistics –Looking carefully at the bullets and cartridge cases to compare and find gun from which bullet was shot. They also take casts of bullet holes.

  14. Blood – Wet body fluids have to be air dried first, and packaged separately in paper bag. • Stains on surfaces – The item itself is taken for analysis, or a swab is taken with a cotton wool bud. • Samples from suspects – are tubed and placed in the fridge for analysis.

  15. Documents – The ink and signatures are compared along with paper type, etc. These are collected and bagged appropriately.

  16. Fibres and hairs – Visual searches, searches using different lighting and microscopical searches are made for fibre collection. • Picking, taping, scraping and vacuuming are used to collect evidence.

  17. Fingerprints – Dusting, Iodine fuming, Ninhydrin spray, Silver nitrate (both work with sweat) and superglue fuming are used.

  18. Footprints and tyreprints – Taking plastercasts and photos.

  19. Glass – Take samples of glass in sealed bags from the area.

  20. Paint – Careful removal of paint is required so that all layers of paint are removed.

  21. Plastic – Collected by rubbing sandpaper or emery board over them. Details for different cars can be collected from plastics used for car bumpers.

  22. Pollen – Collected using cotton wool buds, and then viewed under a microscope.

  23. Soil – Needs to be dried and then placed in individual paper bags. It should also be taken from the area at the same depth as the suspects shoe would go.

  24. Teeth – are collected and bagged at the scene of a crime. Teeth marks and bite are recorded using photography and visual examination.

  25. How is contamination prevented on each type of evidence during collection? Alcohol, Drugs and Toxicology, Arson, Ballistics, Blood, Documents, Explosives, Fibres, Fingerprints, Footprints and tyreprints, Glass, Hair, Paint, Plastic, Pollen, Soil and teeth.

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