Do Now: 1. A victim was found at 4:30 p.m. with a temperature of 34 degrees Celsius. Approximately, what time did this victim die? ( include each step) Reference Table, More or Less, Organize, Rate, Equation 2. Would hair be classified as individual evidence or class evidence? Why? Objective: SWBAT demonstrate knowledge on how the human body can be identified by skeletal remains (unit 3). SWBAT identify the various parts of a hair and SWBAT explain how hair can be used in a forensic investigation (unit 4)

REVIEW What is Locard’s Exchange Principle? There is always transfer of evidence between suspect and victim or area

Hair Shedding!!! Did you know your hair sheds at a rate of 100 strands per 24 hours?!?!

Parts of the Hair Cuticle- tough, clear outside covering Cortex- middle layer that provides strength Medulla- Spongy interior that provides flexibility 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.

Hair is composed of three principal parts: Cuticle – outer coating composed of overlapping scales Cortex – protein-rich structure around the medulla that contains pigment Medulla – central core (may be absent)

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: Image: 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.

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: Image: Hair Structure

The Cortex Contains pigment that gives your hair it’s color The absence of this pigment makes hair grey or white

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. 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

Hair and the Crime Scene

Hair and Fibers at the Crime Scene Investigators consider these to be “trace evidence”

What Happens When Hair or Fibers are Discovered? First Investigators need to determine if it is human or animal If it’s human, investigators need to narrow it down to a group of individuals who could be the suspects

What We Can Learn From Hair Samples Whether or not the source is animal or human Racial Origin Location on the Source’s Body Whether the hair has been chemically treated Color Whether the hair was forcefully removed

Hair as a Chemical Indicator Your hair is capable of collecting materials that come into your body via the blood stream and are delivered to your hair root and deposited in the cortex Many drugs, vitamins, and poisons can be detected in just a few millimeters of hair

Why do Fibers Have to Go Through So Many Tests? So many of the same fibers are found on a lot of textiles

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. Natural Fibers

Images: 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 Synthetic Fibers Fibers under a microscope

Fiber Transfer Primary Transfer Secondary Transfer

Primary Transfer AKA “direct transfer” Fiber transfers from a fabric source like a carpet, bed, or furniture at a crime scene

Secondary Transfer Already transferred fibers on the clothing of a suspect transfer to the clothing of a victim

Does Fiber Transfer Always Occur? NO!! Certain types of fabrics do not shed well

Fiber Analysis Various tests can be performed on fibers to determine their properties.

1. Burn Test Fibers burn differently, produce different odors when burned, and have different ash/residue appearances

2. Thermal Decomposition When fibers are gently heated, they often break down/ decompose into their simpler units

3. Chemical Tests Solubility and chemical decomposition properties are different based on fabrics are made of.

4. Microscopic Examination Getting a closer look at a fiber under a microscope to determine it’s properties

FIBER LAB Take several pieces of tape and press it against your shirt, sweater, or blouse. Rub it smooth and pull it off slowly and smooth it out on your notebook paper. Repeat the procedure on your pants, skirt, or whatever you’re wearing below your waist. Write in your lab book what fibers and hairs you think you’ll. Label the source of each sample and look at it under the compound microscope. Sketch and label what you see. Classify the hair and fibers (cotton, nylon, pet hair, hair from head, etc). Did you predict the outcome correctly? What type of fabric is the best collector? What type is the worst?