1. Fiber and Threads How are fibers found at a scene helpful? How are fibers found at a scene helpful? Why would fibers be less than helpful when found at a scene? Why would fibers be less than helpful when found at a scene?

2. Types of Fibers Natural fibers – derived from plants or animals Natural fibers – derived from plants or animals Manufactured fibers – fibers derived from either natural or synthetic polymers Manufactured fibers – fibers derived from either natural or synthetic polymers

3. Natural Fibers Which type of natural fibers do you think are most often encountered at crime scenes? Which type of natural fibers do you think are most often encountered at crime scenes? Hair Hair Fur Fur Use microscopic analysis to identify Use microscopic analysis to identify What is the most prevalent PLANT fiber? What is the most prevalent PLANT fiber?

4. Cotton Fiber

5. Identification and Comparison of Manufactured Fibers 1 st Step: Microscopic Examination of fibers 1 st Step: Microscopic Examination of fibers – To compare color and diameter – Uses a comparison microscope If negative, no point going further. If negative, no point going further.

6. Microscopic Examination Other features to compare: Other features to compare: Lined markings on the surface Lined markings on the surface Pitting of the surface Pitting of the surface Cross-sectional (???) shape Cross-sectional (???) shape Comparison of dye composition of same-colored fibers Comparison of dye composition of same-colored fibers – Microspectrophotometer – Chromatographic separation of the dye constituents

7. Images – pp.373-374

8. Identification and Comparison of Manufactured Fibers 2 nd Step: Chemical Composition to determine and compare what class of fibers each sample belongs to. 2 nd Step: Chemical Composition to determine and compare what class of fibers each sample belongs to. 3 rd Step: Other, more complicated tests 3 rd Step: Other, more complicated tests

9. Significance of Fiber Evidence Does a fiber match mean the fiber came from the garment in question? Does a fiber match mean the fiber came from the garment in question? What are the chances that a match - including size shape, microscopic appearance, chemical composition, and dye content - would be wrong? What are the chances that a match - including size shape, microscopic appearance, chemical composition, and dye content - would be wrong?

10. Collection of Evidence How? How? Bag whole articles separately – clothing, bedding, carpets, car seats, etc. Bag whole articles separately – clothing, bedding, carpets, car seats, etc. Remove stray fibers Remove stray fibers Either way, VERY tedious and time-consuming Either way, VERY tedious and time-consuming

11. Forensics at Work Jeffrey MacDonald Jeffrey MacDonald The Telltale Rabbit The Telltale Rabbit