Documentation & Trace Analysis Flashcards
Define chain of custody and why it is important.
Chain of custody is the chronological documentation of the movement of the evidence.
Prevents samples from being deemed useless and contaminated in court
What is trace evidence?
Occurs when different objects contact one another. Usually evidence not visible to the eye. Can include: Finger prints Hair Cosmetics Fibres Soil Paint Residue
Examples of Trace evidence
Finger prints Hair Cosmetics Fibres Soil Paint Residue
What is Locard’s principle?
Every contact leaves a trace
What are the methods of collection?
Specific materials all have different collection methods. Handpicking Tape Lifting Brushing/Shaking Vacuuming Swabbing Bagging (beadspace collection)
What are the types of paint?
Domestic/architectural
Automotive
What kind of cases involve paint examination?
Motor vehicle accidents
Hit and run (car x car or car x other)
Property damage
Break and enter
What is a binder?
Coating that allows pigment to distribute across the surface
What is a solvent?
It dissolves the binder and allows the paint to have a consistency suitable to use.
What is a special-purpose coating?
Coating used to fulfil a specific need and has another purpose other than protection and aesthetic
I.e. waterproofing, skidmarks
When does paint transfer occur?
When heat/friction and/or pressure being applied between 2 objects.
Can occur as droplets or spillage
Explain what one way and two way transfer of paint occurs.
One way: Vehicle A only transfers paint to vehicle B
Two Way: Vehicle A and B transfer paint onto each other
Explain the process of paint examination with Optical Microscopy?
Allows a visual microscopic view of the different layers of paint
Explain Infrared Microscopy
Provides information about binder types and fillers/pigments
What is UV VIs
It is a tool used to look at pigments as the human eye often cannot distinguish between two closely related colours.
What is SEM/EDX?
The elemental and inorganic analysis of paints and coatings.
I.e. aluminium, magnesium detection
-Scanning electron microscopy-energy dispersive X-ray analysis-
What is the refractive index of light?
The way light bends and retracts as it travels through glass
- Why type of fibres have low evidentiary value
○ White cotton fibres and blue cotton denim fibres
- How are documents for evidence handled and packaged?
○ Documents, handled with care to preserve their original form and condition
○ Plastic covers/envelopes are used
Packaging of Evidence
- Ignitable Liquid residues: air tight tins or cryovac bags. Brown paper bag must NOT be used.
- Glass: not in plastic = mouldy; control samples in plastic pots, not glass vials.
- Globes: protected w cotton wool to preserve damage.
- When are fingerprints detected on document evaluation?
○ After document examination to prevent bleeding of the ink
- How are obliterated document entries revealed?
○ Using optical enhancements
How are indented impressions detected on documents?
Electrostatic Detection Apparatus (ESDA).
is used to produce a permanent ‘lift’ from paper which provides a visual map of indented impressions in that paper.
- What are the different types of glass examination used in forensic investigation?
○ Refractive indexes
○ GRIM- Glass Refractive Index
Measurement-compares glass.
○ Inorganic analysis
- How is handwriting analysed and examined?
○ It is analysed using known exemplars and comparing it to the unknown (the document in question) to find matching characteristics in the handwriting
- What are the characteristics found in handwriting?
○ Spacing between letters ○ Spacing between word ○ Relative proportions between letters and within letters ○ Individual letter formations ○ Pen lifts
- What is a single magnifying system?
a. Single lens used to form an enlarged image of an object.
- What is a compound magnifying system?
a. Where magnification occurs in 2 stages.
A compound microscope provides a two-dimensional image, while a stereo microscope provides a three-dimensional image.
What methods are used to differentiate fibres?
- Polarised light Microscopy - Information about the production and finishing of the fibre after spinning.
- Refractive index- How thick the fibre is.
- Birefringence- Similar to RI.
- Fluorescent microscopy- Detecting colour.
