1 / 21

DECEMBER 5, 2012 EQ: How can synthetic fibers be used to solve crimes? WARM-UP:

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.

arnold
Download Presentation

DECEMBER 5, 2012 EQ: How can synthetic fibers be used to solve crimes? WARM-UP:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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.

  2. Can you identify the animal hairs shown? A B C D G E F H I • Think About It … • 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?

  3. Types of Animal Hairs - Key Cat Horse Pig Human A B C D G E F H I Deer Dog Rabbit Rat Human All All but two (B & I) Medulla absent or present, shape of medulla, cuticle, diameter of medulla, etc.

  4. Microscopic Evidence and Its Analysis - Root Characteristics: Removal Pulled Forcibly removed Shed - Tip Characteristics Burned Cut Razored Split

  5. 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 crosstransfers 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.

  6. Natural Fibers 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. http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm

  7. What are some common natural fibers that come from animals?

  8. Fibers under a microscope Synthetic (Manufactured) Fibers 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 Images: http://www.trashforteaching.org/phpstore/product_images/YarnWS.JPG http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidencehttp://www.jivepuppi.com/images/fiber_evidence.jpg

  9. 5 Characteristics used to identify Fibers: Color (comparison microscope) Diameter (comparison microscope) Lengthwise striations Pitting of fibers surface Cross-sectional shape

  10. More than half of which fibers are used to make fabrics?

  11. 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

  12. 3 Challenges in Identifying Fiber Evidence: No analytical technique to trace a fiber to a single garment with certainty No databases for fibers origin Mass distribution of fibers and changing fashions

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

  14. Which fiber analysis technique involves separating dyes to see patterns of color?

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

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

  17. Can you identify the types of fibers shown? A B C D E F • Think About It … • Which samples are natural fibers? • (2) Which samples are synthetic fibers? • (3) What characteristics can be used to identify fiber samples?

  18. Answer Keys http://micro.magnet.fsu.edu/primer/techniques/polarized/gallery/images/humansmall.jpg

  19. Types of Fibers - Key A B C Acrylic Yarn Cotton Yarn Nylon Rope D E F Polyester Yarn Rayon Rope Wool Yarn

More Related