DECEMBER 5, 2012 EQ: How can synthetic fibers be used to solve crimes? WARM-UP: The following slide will have 9 pictures (A-I). Identify the animal hair shown and answer the questions. You may use the pgs in Ch 10 (blue)/11 (orange) of your book.

Can you identify the animal hairs shown? Think About It … (1)In which samples are we viewing the cuticle? How do they compare? (2) In which samples are we viewing the medulla? How do they compare? (3) What characteristics can be used to identify hair samples?

Types of Animal Hairs - Key ABCD EF G IH CatHorsePigHuman DeerDogRatRabbitHuman 1.All 2.All but two (B & I) 3.Medulla absent or present, shape of medulla, cuticle, diameter of medulla, etc.

- Root Characteristics: Removal PulledForcibly removedShed BurnedCutRazoredSplit - Tip Characteristics

Fiber Evidence A fiber is the smallest unit of a textile material that has a length many times greater than its diameter. Matching unique fibers on the clothing of a victim to fibers on a suspect’s clothing can be very helpful to an investigation. The discovery of cross transfers and multiple fiber transfers between the suspect's clothing and the victim's clothing dramatically increases the chances that these two individuals had physical contact.

Many different natural fibers that come from plants and animals are used in the production of fabric. (Wool, mohair, cotton, cashmere, mink, etc.) Cotton fibers are the plant fibers most commonly used in textile materials. Cotton fibers have a ribbon-like shape with twists at irregular intervals. The animal fiber most frequently used in the production of textile materials is wool, and the most common wool fibers originate from sheep. Natural Fibers

Images: More than half of all fibers used in the production of textile materials are synthetic or man-made. Nylon, rayon, spandex, and polyester are all examples of synthetic fibers. Cross-section of a man-made fiber Synthetic (Manufactured) Fibers Fibers under a microscope

5 Characteristics used to identify Fibers: 1.Color (comparison microscope) 2.Diameter (comparison microscope) 3.Lengthwise striations 4.Pitting of fibers surface 5.Cross-sectional shape

Analytical Techniques used in Fiber Examination: Visible-light micro spectrophotometer- compare colors of fivers through spectral patterns Chromatography- Separating colors in dyes that come from the fibers for comparison Chemical composition- Test for chemical make-up of fibers to see if they are in the same class Birefringence- Double refraction (two bends), when substance is melted & crystallized Infrared Light- Use of a microscope and infrared spectrophotometer for infrared analysis

3 Challenges in Identifying Fiber Evidence: 1.No analytical technique to trace a fiber to a single garment with certainty 2.No databases for fibers origin 3.Mass distribution of fibers and changing fashions

Collection & Preservation of Fiber Evidence: 1.Clothing packaged in paper bags 2.Carpet, rugs, & bedding folded carefully 3.Articles shouldn’t be placed on same surface 4.Loose fibers removed and placed on paper, folded and labeled

HAIR & FIBERS DRAWINGS: Draw the following fibers and include the following: 1.Specimen name (Dog, cat, etc.) 2.Magnification (100x, 400x, etc.) 3.Contain a Medulla 4.Is medulla continuous, fragmented, or interrupted? HAIR: Human Dog Deer Rabbit Cat Mouse

Draw the following NATURAL & SYNTHETIC fibers as seen under a microscope and include the following: 1.Specimen 2.Magnification 3.One characteristic 4.Uses (at least two) Cotton Wool Mohair Rayon Polyester Spandex

Can you identify the types of fibers shown? Think About It … (1)Which samples are natural fibers? (2) Which samples are synthetic fibers? (3) What characteristics can be used to identify fiber samples?

Answer Keys

Types of Fibers - Key Acrylic YarnCotton YarnNylon Rope Polyester YarnRayon RopeWool Yarn