Fibers and Textiles

1. Fibers and Textiles

2. Fibers as Evidence • Fibers provide circumstantial or indirect evidence that can link a suspect to a crime scene • Example: a thief may own a jacket that matches fibers found at a crime scene • Fibers are considered class evidencesince they are not specific to a single person • Most fibers are small or found in small amounts so they also are considered trace evidence

3. Checkpoint • Classify fibers as… • Direct or circumstantial (indirect) evidence • Individual or class evidence

4. Fibers as Evidence • Fibers may originate from carpets, clothing, linens, furniture, insulation, or rope ect… • Fibers naturally shed from these items • Fibers are easily transferred or “picked up” • Fibers may be transferred from a victim to a suspect, this is called direct transfer • Example: Fibers from victim’s sweater found on suspect • If fibers are picked by victim and then transferred to suspect it is called secondary transfer. • Example: Victim picks up fibers from his/her couch earlier in day and then transfers to the suspect later

5. Checkpoint • Explain the difference between direct and secondary transfer

6. Time is of Essence • Early collection of fibers in an investigation is critical • Within 24 hours an estimated 95% if all fibers may have fallen off a victim or been lost from a crime scene • Only fibers not expected to be found at a crime scene are investigated

7. Something to Ponder • Police no longer cover dead bodies with cotton sheets at a crime scene. Why?

8. The Value of Fibers • The value of fiber evidence in an crime investigation depends upon its potential uniqueness • Example: a white cotton fiber has less value than an orange wool fiber

9. Not just Your Pets Shed! • Textile Shedding • The most common form of fiber transfer to be encountered is the shedding of a textile • Textile (fabric) = a flexible, flat material made by interlacing yarns • Clothing, carpets, upholstery ect… • Fibers are short are spun into yarn, individual fibers can there be pulled away or shed from fabric

10. Weave Pattern • Yarns and fibers are woven into textiles or fabrics • 5 Major types of weave pattern for textiles • Plain • Basket • Satin • Twill • Leno • Warp and Weft determines weave pattern • Warp = length wise fiber • Weft = crosswise (vertical fibers)

11. Weave PatternsPLAIN • Plain • Alternating warp and weft pattern • Single fibers

12. Weave PatternsBASKET • Basket • Alternating warp and weft pattern • Double fibers- 2 weft threads crossing to warp threads

13. Weave PatternsSATIN • Satin • Wefts are woven over 3 or more warp threads at a time

14. Weave PatternsTWILL • Twill • Weft is woven over 3 or more warps and then under one • Next row the pattern is shifted over one to the left or right by one warp thread

15. Weave PatternsLENO • Leno • Use two warp threads and a double weft thread • To adjacent weft threads cross over each other

16. Thread Count • Thread Count • In addition to weave pattern, textiles or fabrics also differ in thread count • Thread Count = threads per inch • Example- bed sheets • Often 180,200,400 or even 500 • Higher thread count = higher price