Forensic Science

1. Hairs & Fibers Forensic Science http://media.popularmechanics.com/images/PMX0706FORENSICSHairSmall.jpg Presentation developed by T. Trimpe 2006 http://sciencespot.net/

2. Biology of Hair Hair is composed of the protein keratin, which is also the primary component of finger and toe nails. Hair is produced from a structure called the hair follicle. Humans develophair follicles during fetal development, and no new follicles are produced after birth. Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light. Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc.). The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample’s length, shape, size, color, and other physical characteristics. In order to test hair evidence for DNA, the root must be present. Sources: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair & http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Index%20(Hairs)

3. Medulla – central core(may be absent) Cortex – protein-rich structure around the medulla that contains pigment Hair Structure Hair is composed of three principal parts: Cuticle – outer coating composed of overlapping scales The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside. http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

4. Hair Structure • Cuticle • The cuticle varies in: • Its scales, • How many there are per centimeter, • How much they overlap, • Their overall shape, and • How much they protrude from the surface • Its thickness, and • Whether or not it contains pigment. Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people. Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.hairdressersus.com/micro/Image5b.jpg

5. Hair Structure • Cortex • The cortex varies in: • Thickness • Texture • Color • Distribution of the cortex is perhaps the most important component in determining from which individual a human hair may have come. • Microscopic examination can also reveal the condition and shape of the root and tip. Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.extrapersonality.com/hair.html

6. Like the cuticle, the medulla can be important for distinguishing between hairs of different species, but often does not lend much important information to the differentiation between hairs from different people. Hair Structure • Medulla • The medulla may vary in: • Thickness • Continuity - one continuous structure or broken into pieces • Opacity - how much light is able to pass through it • It may also be absent in some species. http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

7. Hair shaft shape • Caucasian – hair shafts are usually oval to round • Negroid – is flat in shape • Mongoloid – is rounder in shape

8. Species & Conditions of Hair bsapp.com

9. Human Hairs bsapp.com

10. Horse Hair Cuticle is smooth Continuous thick medulla bsapp.com

11. Dog Hair bsapp.com

12. Cat Hair Medulla looks like a sting of beads bsapp.com

13. Mouse Hair bsapp.com

14. Rabbit Hair bsapp.com

15. Deer Hair bsapp.com

16. Cow Hair bsapp.com

17. Data base of Hair Images http://www.iamaweb.com/Animal_Hair/animal_hair_images.html

18. Special Conditions of Hair The following slides show the ends of several different species of hairs bsapp.com

19. Fallen Out Hairs bsapp.com

20. Natural Tip bsapp.com

21. Pulled Out-By the Root bsapp.com

22. Broken-Torn bsapp.com

23. Cut Hair bsapp.com

24. Cuticles The following pictures were taken with the an electron scanning microscope bsapp.com

25. Human Hairs bsapp.com

26. Human Hair with Gel bsapp.com

27. Cat Hair bsapp.com

28. Cow Hair bsapp.com

29. Deer Hair bsapp.com

30. Dog Hair bsapp.com

31. Mouse Hair bsapp.com

32. Pig Hair bsapp.com

33. Rabbit Hair bsapp.com

34. Squirrel Hair bsapp.com

36. Types of Animal Hairs - Key Cat Horse Pig Human A B C D G E F H I Deer Dog Rabbit Rat Human

37. Fiber Evidence A fiber is the smallest unit of a textile material that has a length many times greater than its diameter. A fiber can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric. The type and length of fiber used, the type of spinning method, and the type of fabric construction all affect the transfer of fibers and the significance of fiber associations. This becomes very important when there is a possibility of fiber transfer between a suspect and a victim during the commission of a crime. Matching unique fibers on the clothing of a victim to fibers on a suspect’s clothing can be very helpful to an investigation, whereas the matching of common fibers such as white cotton or blue denim fibers would be less helpful. The discovery of crosstransfers and multiple fiber transfers between the suspect's clothing and the victim's clothing dramatically increases the likelihood that these two individuals had physical contact. http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence

38. Natural Fibers Many different natural fibers that come from plants and animals are used in the production of fabric. Cotton fibers are the plant fibers most commonly used in textile materials 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

39. Fibers under a microscope Synthetic Fibers More than half of all fibers used in the production of textile materials are synthetic or man-made. Nylon, rayon, 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

40. ID & Comparison of Man-Made Fibers • First step…? • Microscopic comparison for color and diameter using a comparison microscope • Other morphological features • lengthwise striations • pitting of the fibers surface with delustering particles (titanium dioxide) • Reduce the shine • Cross section of the fiber (reveals certain shape)

41. ID & Comparison (cont.) • More detailed analysis…what technique? • Small strands of fibers are compared for dye content by usingchromatography • First – extract the dye off each fiber with a solvent • Then – spot the dye solution onto a thin-layer chromatography plate • End Result: The components of the questioned and standard/reference dye will separate on the thin-layer plate and then can be compared for similarities

42. ID & Comparison (cont.) • Analysis (cont.) • After the TLC is complete the fibers must be shown to have the same chemical composition • before any conclusions are reached • Must show that the suspect fibers belong to the same broad generic class and more specific subclass • Ex: nylon has 4 subclasses which may differ in physical shape, appearance and dyeability • Ex: Acrylics can be divided into 24 groups on the basis of the structure of their polymers structure and microscopic characteristics

43. ID & Comparison (cont.) • Techniques used to examine a small sample size • Double refraction • When a beam of light is refracted into 2 different light-ray components • Gives rise to a double image • Each light ray has a different refractive index value • the mathematical difference between these 2 values is the … • birefringence • How is it done? • place the fiber into a fluid that has a comparable refractive index • observe the disappearance of the Becke line under a polarizing microscope • Benefit • A single tiny fiber can be analyzed without being damaged

44. ID & Comparison (cont.) • ID Techniques (cont.) • Infrared Spectrophotometry • The polymers that make up manufactured fibers will absorb IR light in a characteristic pattern • Rapid and reliable for identification of the generic class and sometimes the subclass

45. Fiber Comparison Can you tell the difference(s) between the cotton on the left and the rayon on the right?

46. Weave Patterns

47. Knitted Fabric Knitted fabrics are made by interlocking loops into a specific arrangement. It may be one continuous thread or a combination. Either way, the yarn is formed into successive rows of loops and then drawn through another series of loops to make the fabric.

48. Collection & Preservation – Fiber Evidence • Relevant articles of clothing should be packaged in separate paper bags • Carpets, rugs and bedding are to be folded carefully to protect areas suspected of containing fibers • Car seats should be covered with polyethylene sheets to protect fiber evidence • Knife blades should be covered to protect adhering fibers • If there is a body thought to have been wrapped in a blanket or carpet, adhesive tape lifts to the exposed areas may reveal fiber strands

50. Fiber Challenge • A = acrylic yarn • B = Cotton • C = nylon • D = polyster • E = rayon • F= wool