Hair Analysis. By the end of this unit you will be able to:

Transcription

1 1 All rights Reserved Cengage/NGL/Suth-Western 2016

2 Hair Analysis By the end f this unit yu will be able t: 1 Identify the varius parts f a hair. 2 Describe variatins in the structure f the medulla, crtex, and cuticle. 3 Distinguish between human and nnhuman animal hair. 4 Explain hw hair can be used in a frensic investigatin. 5 Calculate the medullary index fr a hair. 6 Distinguish hairs frm individuals belnging t brad racial categries. 2

3 Vcabulary cmparisn micrscpe crtex cuticle gas chrmatgraphy hair shaft keratin medulla melanin granules mitchndrial DNA (mtdna) nuclear DNA hair fllicle 3

4 Intrductin Hair can yield class evidence. A hair withut the fllicle and its nuclear DNA cannt prvide individual evidence. Chemical tests perfrmed n hair can reveal drugs, txins, heavy metals and nutritinal deficiencies. Mitchndrial DNA (mtdna) frm hair can reveal sme f a suspect s r victim s family relatinships. 4

5 5

6 The Functins f Hair Regulates bdy temperature gsebumps trap warm air under upright hair Decreases frictin Prtects against sunlight Acts as a sense rgan Humans are brn with abut 5 millin hair fllicles. 6

7 The Structure f Human Hair Human hair cnsists f a fllicle and a shaft. 7

8 The Structure f Human Hair (cntinued) The hair shaft is made up f three layers: An inner medulla A crtex An uter cuticle 8

9 The Structure f Human Hair (cntinued) The cuticle is a transparent uter layer f the hair shaft. Have different shapes/patterns depending n species f mammal Scales pint frm scalp t end, which helps determine yunger and lder hair 9

10 Crtex: Thickest layer Cntains mst f the pigment Distributin f pigment varies Usually denser nearer the cuticle

11 11 Types f Medulla

12 Types f Hair In humans, hair varies frm persn t persn, and even varies depending n its lcatin n a particular persn. Fr an individual persn, hair can vary based n its lcatin n the bdy. T cmpensate fr incnsistencies that ccur, 50 hairs are usually cllected frm a suspect s r victim s head. 12

13 Types f Hair Hair can vary in: Shape Length Diameter Texture Clr

14 Hair frm Different Parts f the Bdy Human hair varies n the bdy 1. Head Hair 2. Eyebrws and Eyelashes 3. Beard and Mustache Hair 4. Underarm Hair 5. Bdy hair (Auxiliary Hair) 6. Pubic Hair

15 15 Hair frm Different Parts f the Bdy

16 The Life Cycle f Hair Hair prceeds thrugh three stages as it develps. Anagen stage: (80-90% f hair) hair actively grws cells arund the fllicle rapidly divide and depsit materials in the hair Lasts apprximately 1000 days 16

17 The Life Cycle f Hair (cntinued) Catagen stage: (2% f hair) The hair stps grwing Fllicle recedes Can change / turn grey Telgen stage: (10 18% f hair) Fllicle becmes drmant Hairs are easily lst 17

18 Treated Hair Hair can be treated in many different ways Dyed, bleached, relaxed Chemicals remain Changes can be detected by micrscpe 18

19 Ethnic r Ancestral Differences There are sme key physical characteristics that are assciated with hair f different ancestral grups. 19

20 Racial Differences Brad racial categrizatin can be made by identifying certain characteristics f hair. These characteristics may NOT be applicable t all individuals in these grups. Therefre, Individual hairs CANNOT be assigned t any f these grups 20

21 Animal hair and Human Hair Animal hair and human hair have several differences including: The pattern f pigmentatin Animal hair is denser tward the medulla, humans tward the cuticle Animals can have banded patterns, humans can t The medullary index The cuticle type 21

22 Hair Cuticles The cuticle f the hair shaft can help distinguish human hair frm ther animal hair. 22

23 Using Hair in an Investigatin Investigatrs ften make bservatins abut the macrscpic and micrscpic features f a hair Micrscpes (especially cmparisn micrscpes) are imprtant tls Mrphlgical characteristics Matching clr, length, diameter, medulla Different micrscpes prvide different kinds f evidence.

24 Micrscpic Assessment Preparatin 24

25 Electrn Micrscpes Direct a beam f electrns at a sample. Prvide magnificatin f 50,000 times r mre. 25

26 Testing fr Substances in the Hair Shaft Sme txins and drugs which an individual has ingested leave traces in the hair. Chemical tests determine presence f varius substances Can calculate the length f time during which a persn was taking drugs r ingesting ther txins. 26

27 Cllectin and Preservatin As a general rule, frensic hair cmparisns invlve either head hair r pubic hair. The cllectin f 50 full-length hairs frm all areas f the scalp will nrmally ensure a representative sampling f head hair. A minimum cllectin f 24 full-length pubic hairs shuld cver the range f characteristics present in pubic hair. Hair samples are als cllected frm the victim f suspicius deaths during an autpsy.

28 Hair Examinatin and Testing DNA is extracted and amplified using PCR. DNA is prfiled using an autmated prcess. mtdna can be used t establish a genetic relatinship thrugh the mther. Suspects can be excluded if their mtdna is nt cnsistent with the crime-scene mtdna. 28

29 29