Bob's Fibres

Question 1

What are the six ways in which fibres differ from eachother?

Answer 1

1. Chemical nature
2. Cross-sectional shape
3. Surface contour
4. Colour
5. Length
6. Diameter

Question 2

What is direct and indirect transfer?

Answer 2

Direct transfer is where the fibre is transferred from the fabric directly onto the victim/suspect

Indirect transfer is where the fibre has already transferred onto the clothing of the suspect or victim and then transfers onto the other party.

Question 3

What are the principles of fibre transfer?

Answer 3

Textile fibres can be exchanged between:

• Two individuals, between an individual and an object or between two objects.

Detection depends on:

• The nature and duration of contact between suspect and victim or crime scene
• Persistence of fibres after transfer
• Types of fabrics involved in contact.

Question 4

What factors influence the propensity of a fibre to shed?

Answer 4

• How a fabric is constructed; tightly woven or knitted fabrics shed less than loosely woven/knitted fabrics.
• Fabrics composed of filament yarns such as silk shed less than fabrics composed of staple yarns such as wool.
• Certain types of fibres transfer more readily; Nylon and polyester shed less than wool and acrylic.
• Worn/damaged fibres caused during physical contact shed more than fabrics made of polyester fibres.

Question 5

What is surface debris taping and what are the limitations of this technique?

Answer 5

Surface debris taping requires one to use transparent adhesive tape and hold it adhesive side down, then systematically dab the surface.

The tape is then stuck down onto an acetate sheet, which is placed in a greaseproof envelope.

If the surface is wet, the fibres will not adhere to the tape, and the method is not efficient on large surfaces.

Question 6

What are the four factors of fibre comparison?

Answer 6

• Mechanical fit - when the fabric is torn, do the two pieces fit together? (conclusive evidence)
• Microscopic comparison of colour, diameter, striations.
• Colour comparison of specific dyes, used with microspectrophotometer or chromatography.
• Chemical composition - make sure fibres are from same generic class and subclass with IR spectrometry

Question 7

When will a trilobal fibre be found?

Answer 7

A trilobal fibre, typically synthetic, is used in carpets as it helps hide dirt and create a specific visual texture to the carpet.

It is produced when a spinning dope is extruded through a spinnerette with lobed holes

Question 8

What are the advantages and disadvantages of TLC?

Answer 8

Advantages: Highly discriminating and an inexpensive way to look at dye batch variation.

Disadvantages: Destructive tests not suitable to examine pale fibres and provides a tentative ID.

Question 9

What 6 factors determine the evidential value of a fibre?

Answer 9

1. The type of fibre; flax is more valuable than cotton
2. The number of fibres transferred.
3. Colour or variation of colour of the fibre
4. Location of the fibres.
5. A number of different fibres.
6. Likelihood of transfer based upon the fibre construction.