Welcome back to Forensics Day 12 Please complete the Tobacco survey and pass up. Do not put your name on it. Working with a partner go to a station with.

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Presentation transcript:

Welcome back to Forensics Day 12 Please complete the Tobacco survey and pass up. Do not put your name on it. Working with a partner go to a station with a microscope and under scanning power (4 X) observe the piece of hair. Record your observations. Do the same thing with a fiber.

Hair & Fiber Analysis

Can be used to match a suspect with a crime scene Can be microscopically analyzed for similarity Comparisons continue to improve as forensic techniques improve

Part 1 Hair Background Grows from a collection of cells called a follicle The hair shaft is composed of three parts: 1.cuticle – outside covering of hair shaft, can look like overlapping roof shingles

Cuticle Imbricate in humans

2.Cortex – inside the cuticle, a pigmented layer 3.Medulla – runs down the center of the hair shaft

Many photos can be obtained from hair dressing publications. Many of the following are from this publication.

Hair texture can vary considerably depending upon the ratio of cuticle to medulla

How a hair grows

Hair fibers are excellent for ID study because: They resist decomposition May indicate drug use or poisoning

Testing for Substances in the Hair Shaft 1. Chemicals that the skin absorbs often can be detected by analysis of the hair shaft. 2. A forensic scientist can perform chemical tests for the presence of various substances. 3. The hair shaft can be examined in sections to establish a timeline for exposure to toxins. 4. Neutron Activation Analysis (NAA) can determine concentrations of substances in the sample.

To distinguish between animal and human hair use a Medullary Index diameter of hair’s medulla Medullary Index = diameter of the hair M.I. = <.33 hair is human M.I. =>.5 or more, hair is animal

Appearance of different hair (or fur) types will vary from animal to animal

Cat hair

Dog hair

Rabbit hair

Other animal hair DeerMuskrat

Deer – no cortex, medulla filled with spheres Mouse – parallel rows of beads

Human Medullary Patterns has three types: Continuous medullary canal Interrupted medulla (regular interruption) Fragmented medulla (interruption irregular)

Hair Photos Can you identify the type of medullary pattern- continuous, interrupted and fragmented?

Caucasoid Oriental Negroid

Hair from different races NegroidMongoloidCaucasoid

Hair cannot be absolutely identified as to race. Traits associated are often and characteristics of races are less distinct.

Some Caucasoid natural colors Dyed hair

Additional Information Individuals of Oriental origin usually have a continuous medulla Dyed hair shows color distributed in cortex and medulla Bleached hair has a yellowish tint As hair grows, natural color returns

Normal hair

Damaged hair BurnedSplit endsRazor cut

Hair is ‘class evidence’ not individual evidence What’s the difference? Varies in texture from one region of the body to another Round or oval in cross-section in Caucasians Oval or flat in cross-section in African Americans

DNA Analysis Only possible if ‘bulb’ at the base of the hair is intact Bulb

Forcibly removed Follicle intactPulled

A Baseline Up to 50 hairs from each body region (head, pubic area, facial hair, etc., are needed to provide a baseline for comparability

Pubic hair

Forensic Examination Obtain samples of crime scene hair samples and compare them microscopically with fibers from four suspects Complete the lab worksheets available

The End…how’s 1.3 going?