whether someone assaulted a victim or was simply going to their aid. deciding what samples to take for DNA analysis in order to establish whom the body fluid could belong to
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Forensic biology at a crime scene
Forensic biology at a crime scene. ensure that all blood has been found using chemical enhancement techniques. interpret bloodstain patterns. electing the most useful stains for DNA analysis
what must you do before using a reagent on a substance
Check & test your reagents•Blood test kits & reagents have a limited shelf-life.•LMG / KM oxidise.•Oxidised LMG / KM appears opaque.•Add a little Zn •Beware H2 generation
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how to test blood using filter paper
•Rub tip of filter paper against stain•Add LMG to tip•Wait >5 secs•If +ve reaction, this is a FALSE reaction•If no reaction, add H2O2
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Search for Obvious blood Stains
economical, at times photograph > drawing. drawing for dark coloured clothing. shoukd consider a range of stains as potential blood and ensure ALL ARE TESTED
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Use Low power microscope (LPM) for Small Stains
useful for searching dark items - using directed light source. “Visual Search Only” on examination notes
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what is a general screen (wipe test)
Wipe unfolded filter paper over a limited area of the item.•Test with LMG. +ve, search area again. Narrow down +ve area. Note +ve area.•Note: Compromises fingerprint evidence!
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what is Direct Test used for
a small particle or fibre can be subjected to a direct (“thread”) test
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how to use a direct test
Place thread on filter paper.•Apply LMG•Then apply H2O2•Retain tested material
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Note Side of Origin
Blood can soak through material.•Always look inside garments (especially I/S cuffs)!•Blood on hands / shoes can transfer to I/S of garments
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Make Contemporaneous Notes
At same time as examinations.•Sign & date.•Must be Fit for Purpose.•Time is money.•General screening may be required if time is a significant factor.
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what to remeber when taking notes
Legibility•Spelling•Grammar•Punctuation
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Discuss Findings With R.O.
doubt about anything, consult a colleague. All significant findings must be confirmed by another scientist. judgement on a finding & this would be discussed & confirmed by at least one other R.O. Both would sign & date their observations
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Check Requirements
before moving on to the next item. Decontaminate work surface & re-package item. All labs have a well organised item storage system
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crime STAIN to court
1.Collect and store evidence from scene 2.Extract DNA 3.Quantify DNA 4.Amplify 5.Separate DNA using electrophoresis 6.Interpret profile 7.Compare one or more profiles for match 8.Present data
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Other cards in this set
Card 2
Front
Forensic biology at a crime scene
Back
Forensic biology at a crime scene. ensure that all blood has been found using chemical enhancement techniques. interpret bloodstain patterns. electing the most useful stains for DNA analysis
Card 3
Front
Other areas of Forensic Biology
Back
Card 4
Front
what must you do before using a reagent on a substance
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