Fibres Flashcards
What are fibres?
Basic unit of yarns and threads which turn into threads, fabrics, textile.
the length significantly exceeds width
Where are they found?
they are ubiquitous
clothing, bedding, carpets, curtains etc
What are natural fibres?
can be plant, animal or mineral based
often termed as “staple” fibres
plant = cotton, linen, hemp, coir
animal = silk, wool, cashmere, angora, camel
mineral = asbestos
What are synthetic fibres?
have a high length to diameter ratio
often termed as “filament” fibres
much longer than natural fibres
e.g polyester, nylon, acrylic
What are the recovery considerations for fibres?
May become dislodged after deposition if the victim is moving or outside (wind)
Air dry wet clothing in controlled and secure environment to maintain the integrity
Store in paper bags not plastic to prevent mould growth
Never package along with debris as debris may adhere so package debris separately!!!
Emergency personnel intervention
How should we recover fibres?
Submit entire item to lab
Perform double packaging
Druggist’s fold for small fibres and then label and then place in another evidence bag
package control sample separately
What is the analytical workflow for fibres?
Gross examination, recovery and collection
Preliminary evaluation of physical characteristics
Physical fit assessment - most probative value, if you can show to pieces of fabric have originated as one and can match them back together.
All microscopic techniques
Micro spectrophotometry (MSP) - colour determination for values
Infrared spectroscopy - manufactured fibres
Raman spectroscopy - dyes and pigments
once these have been done, you can use the destructive techniques such as TLC, HPLC, pyrolysis GC, melting point, micro chemical tests
What characteristics of fibres are we looking for?
Colour - visual, MSP, FTIR/Raman
Length, Diameter and cross sectional profile
Natural or synthetic, and type
Striations and pitting
fading and discolouration
direction of yarn twist
How are fibres interpreted?
Look at the class characteristics
Look at the individual characteristics as these traits can define and identify an item as different to others in the same class
Rarity of fibre increases it’s probative value
Number and location of fibres found - give context and aid in crime reconstruction
Nature of transfer - activity level propositions “fight vs hug”
Substrate considerations
Multiple associations mitigate coincidental transfer - the more fibres you find, the more indicative of true transfer
What are the caveats of fibres analysis?
Can never state that a fibre is unique - use chemo metrics to say how likely/unlikely something is.
Few databases for origin, however, is rapidly changing
expensive, time consuming, skilled analysis
