Forensic Science

1. Hairs & Fibers Forensic Science Unit Aim: How do scientists classify and analyze hair and fibers? http://media.popularmechanics.com/images/PMX0706FORENSICSHairSmall.jpg Presentation developed by T. Trimpe 2006 http://sciencespot.net/

2. Hair Classifications Hair recovered from a crime scene can be valuable evidence. Forensic scientists use color, shape, and distribution of pigment granules to tell the difference between hairs from different individuals. We will learn how to classify several hair samples from animals and humans.

3. Hair Classifications Objectives: Students will be able to:1) analyze morphological characteristics of hair from various sources. 2) distinguish between the three principal parts of hair (cuticle, cortex and medulla).

4. Consider This! Look around the class at students with very similar hair.  If one of these students committed a crime and the only evidence left behind was a strand of their hair, could they be convicted?  Isn’t their hair too similar to differentiate between them with certainty? Or, despite the visible similarities, are there other characteristics of hair that will allow us to individualize the evidence? 

5. 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)

6. 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

7. 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

8. Hair Structure • Cortex • contains pigment granules that give the hair its color • 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

9. Hair Structure • Cortex • contains pigment granules that give the hair its color • The color, shape, and distribution of the granules provide important points of comparison between the hairs of different individuals. • Generally, African American hair is curly and contains unevenly distributed pigment granules. • Caucasian hair is usually straight or wavy, with more evenly distributed pigment granules. Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.extrapersonality.com/hair.html

10. 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 • hollow tube that runs the length of hair • 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

11. Hair Structure • Medulla • hollow tube that runs the length of hair • Sometimes it is present, sometimes not. Sometimes the canal is continuous, while in other cases it is fragmented. • For example, except for the Asian race, human head hairs usually have fragmented medullae or no medullae at all. Among Asians, head hairs generally have continuous medullae. http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

12. Hair Structure • Medulla • Sometimes the hair found at a crime scene is from an animal. This too may be helpful, for it is possible to identify the species. • Different species have different scale patterns on the cuticle of the hair. • Animal hair has a characteristically thicker medulla and cuticle than in a human, since their hair is their means of warmth. http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

13. Hair Identification Activity • http://www.accessexcellence.org/AE/ATG/data/released/0157-theasinclair/Heading4.html

14. Hair Analysis Objectives: Students will be able to: 1) analyze morphological characteristics of hair from various sources. 2) distinguish between the three principal parts of hair (cuticle, cortex and medulla).

15. Hair Analysis Background: The simplest method of hair  identification is visual observation with the naked eye, which can indicate color, length, and amount of curl. Hair can also be examined microscopically to reveal characteristics of its physical structure. Hair is composed of three principal parts: Cuticle – outer coating composed of overlapping scales Medulla – central core, which may be absent Cortex – protein-rich structure surrounding the medulla; contains pigment 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.

16. Hair Analysis Cuticle: • The scales of the cuticle may vary in how many there are per unit of measure, how much they overlap, their overall shape, and how much they protrude from the surface. • The thickness of the cuticle may vary as well, and the cuticles of some species’ hairs may contain 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.

17. Hair Analysis Medulla: • The medulla may vary in thickness, continuity (one continuous structure or broken into pieces), and opacity (how much light is able to pass through it). • It may also be absent. • 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.

18. Hair Analysis Cortex: • The cortex varies in thickness, texture, and color and distribution of pigments. • 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.

19. Hair Analysis • Hair color is mostly the result of pigments -- chemical compounds which reflect certain wavelengths of visible light. • There are two main pigments found in human hair: eumelanin, which gives color to brown or black hair and pheomelanin, which produces the color in blonde or red hair. • Hair color may also be influenced by the optical effects of light reflecting and bouncing off the surfaces of the different hair layers. • Hair shape (round or oval cross-section) and texture (curly or straight) is influenced heavily by genes. • However, nutritional status and intentional alteration (heat curling, "perms") can affect the physical appearance of hair.

20. It’s time to examine some hairs and fibers! http://micro.magnet.fsu.edu/primer/techniques/polarized/gallery/images/humansmall.jpg

21. Hair Analysis Hair Analysis Activity: Each team of students gets a set of 5 labeled envelopes containing hair from different species. Prepare wet mount slides to compare morphological characteristics. Individual hair samples might include the following: 1) human hair (red, long, curly)2) dog hair (black, straight)3) cat hair (grey, long)4) deer hair5) dog hair (white, wiry)6) cat hair (beige, short)7) human hair (brown, straight, short)8) rabbit hair9) human hair (blonde, wavy, long)10) horse hair Adapted from Hair Analysis, http://library.thinkquest.org/04oct/00206/lesson.htm#s_blood

22. Hair & Fiber Identification Lab Directions: Your team will need to use a microscope to document all the hairs and fibers in your set. Write the name of the hair or fiber on the line and then draw what you see under medium or high power. Be sure to indicate the power of magnification! Add a description that highlights the unique characteristics of each hair and fiber sample. Pay attention to details to help you identify samples during the Hair & Fiber Challenge activity.

23. 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?

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

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

26. 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

27. 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

28. 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

29. 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?

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

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