Presentation on theme: "4/21/20151 Trace Evidence Any small pieces of material, naturally occurring or man-made."— Presentation transcript:
4/21/20151 Trace Evidence Any small pieces of material, naturally occurring or man-made.
2 Hair as Evidence Abundant (very common) Time will not change it Easily lost Mostly class evidence. Used most often for sexual assault and violent assault
3 Hair as Evidence Human hair is one of the most frequently found pieces of evidence at the scene of a violent crime – 31. It can provide a link between the criminal and the crime. Hair is not living tissue. (14.) From hair one can determine (29.): If the source is human or animal Race (sometimes) Origin of the location on the source’s body Whether the hair was forcibly removed If the hair has been treated with chemicals If drugs have been ingested
4 Hair Morphology The Study of Structure and Form Parts of the hair u Shaft--part of the hair that sticks out of the skin u Root--lies below the epidermis u Follicle—organ from which the hair grows (source of DNA)
6 Hair Shaft Composed of: Cuticle—outside covering, made of overlapping scales Cortex—inner layer made of keratin and imbedded with pigment; also contains air sacs called cortical fusi Medulla—inside layer running down the center of the cortex
7 Hair Cuticle The cuticle is the outermost layer of hair which is covered with scales. Scales always point toward the tip of the hair. These scales differ between species of animals and are named based on their appearance. 25. Usually scale impressions are made in fingernail polish or similar material then they are viewed under the microscope.
15 Hair Cortex The cortex is made up of spindle-shaped cortical cells that are aligned parallel to the length of the hair, giving the hair its shape. It has two major characteristics: u Melanin--pigment granules that give hair its color u Cortical fusi--air spaces, usually found near the root but may be found throughout the hair shaft
16 The medulla is the central canal running through the hair core that is not always present. The medulla comes in different types and patterns. Types: u Continuous u Intermittent or interrupted u Fragmented u Absent--not present Hair Medulla
18 Medullary Index The index measures the diameter of the medulla relative to the diameter of the hair shaft. Medullary Index for human hair is generally less than 1/3. For animal hair, it is usually greater than 1/2.
24 Hair Root The hair root is the end in the follicle from which the hair grows. The length of hair grows 0.5 mm per day or 1 centimeter per month. There are three phases of hair growth: Anagen --hair that is growing up to 6 years; root has a flame shaped appearance and may have a follicular tag from which DNA may be obtained. Catagen --hair at rest for 2-3 weeks; has elongated appearance Telogen --hair growth is ended; has club shaped appearance.
25 Anagen Forcibly removed hair shows damage and stretching of the root Fallen out Forcibly removed 13 &15. Follicular tag - Attached living tissue (only source of DNA)
26 Catagen Dormant, resting root gets longer and thinner.
27 Telogen Naturally shed hairs display club shaped root
33 Hair Identification Comparison u Length u Diameter u Color intensity of pigments granules u Dyed hair has color in cuticle and cortex u Bleaching removes pigment and gives yellow tint
34 Hair Identification Origin of Human Hair u Head hair- shows little diameter variation and more uniform distribution of pigment color Beard hair- coarse and have blunt tips due to being cut u Pubic hair- short and curly, with wide variation in shaft diameter, or buckling, and have a continuous medullae
35 Tips of Hair Blunt if recently cut Rounded if cut and allowed to grow Blackened or frayed show presenc of a flame If broken end will be irregular Broken Razor Cut Old Cut Burnt New Scissor Cut
36 Hair Shape Can be straight, curly or kinky depending on the cross-section, which may be round, oval or crescent-shaped Round (Straight) Oval (Curly) Crescent moon (Kinky)
37 Determination of Race Black/African hairs are kinky, containing dense, unevenly distributed pigments, diameter is elliptical and varies in size
38 Caucasian hairs are straight or wavy, with very fine to coarse pigments that are more evenly distributed, oval diameter which varies in size
39 Asian Hair Usually round constant diameter Thick cuticle Prominent medulla Pigments are dense and often arranged in large patches
40 Hair Identification Determination u Age and Sex- only infant’s hair can be determined; sex cannot be determined u Individualization - DNA analysis could provide a link from questioned hair to standard hair (follicular tag actually the source not the hair itself)
41 These 3 methods can be done at the crime scene or in the crime lab. 1.Visual Inspection Use naked eye or hand lens. Evidence removed and packaged for later analysis Use bright light and forceps to collec Collection of Trace Evidence
42 Small paper envelopes are bad (Holes allow small objects to escape). Use small plastic bags, glass vial or paper using a druggist fold. Double package. Label each package. Packaging from Visual Inspection
43 Clear tape is used. Repeatedly apply tape to small area until most of the stickiness is gone. Tape is folded back upon itself, taped to a glass slide or taped to a piece of plastic. Put in separate labeled container. Be sure to document specific area covered. 2. Tape Lift 36. Collection
44 3. Vacuuming Nozzle should be short and transparent. Debris is collected on a filter or membrane Small area is vacuumed. (Filters changed frequently) Filters packaged in separate labeled container. (Be sure to document specific area covered) Most improperly used method because it often results in the collection of a lot of irrelevant material.
45 Collection of Hair Evidence Questioned hairs must be accompanied by an adequate number of control samples. from victim possible suspects others who may have deposited hair at the scene Control Sample 50 full-length hairs from all areas of scalp 24 full-length pubic hairs
46 Hair Toxicology Advantages: Easy to collect and store Is externally available Can provide information on the individual’s history of drug use or of poisoning. Collections must be taken from different locations on the body to get an accurate timeline.
47 Hair Toxicology Napoleon died in exile in 1821. By analyzing his hair, some investigators suggest he was poisoned by the deliberate administration of arsenic; others suggest that it was vapors from the dyes in the wallpaper that did him in.
52 Types of Fibers-Classification Man-made u Regenerated u Synthetic Natural u Animal - Protein u Plants- Vegetable u Excrement u Mineral
53 TYPES NATURAL FIBERS Animal or Protein sheep (wool) goats (mohair, cashmere) camels llamas alpacas vicunas Fur fibers: mink, rabbit, beaver, and muskrat
54 Polymers Polymers are basic chemical substances of all synthetic fibers, long-chained molecules Monomers-repeating molecular units of polymers Importance- Synthesize many new items including glues, plastics, paints and fibers
55 Collection of Fiber Evidence Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged. Make tape lifts of exposed skin areas of bodies and any inanimate objects Removed fibers should be folded into a small sheet of paper and stored in a paper bag
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