Do Now:

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)

REVIEWWhat 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 HairCuticle- 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 StructureHair is composed of three principal parts:

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

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: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.hairdressersus.com/micro/Image5b.jpg

Hair Structure

CuticleThe 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: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.extrapersonality.com/hair.html

Hair Structure

The CortexContains pigment that gives your hair it’s color

The absence of this pigment makes hair grey or white

MedullaThe 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

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

http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

Day 2Hair and the Crime

Scene

Hair and Fibers at the Crime SceneInvestigators 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 SamplesWhether or not the source is animal or

humanRacial OriginLocation on the Source’s BodyWhether the hair has been chemically treatedColor Whether the hair was forcefully removed

Hair as a Chemical IndicatorYour 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.

http://www.fireflydiapers.com/articles/diaperarticle_naturalfibersabsorb.htm

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: http://www.trashforteaching.org/phpstore/product_images/YarnWS.JPG http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric3.htm#Fiber%20Evidence

http://www.jivepuppi.com/images/fiber_evidence.jpg

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 TransferAKA “direct

transfer”

Fiber transfers from a fabric source like a carpet, bed, or furniture at a crime scene

Secondary TransferAlready 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 AnalysisVarious tests can be performed on fibers to

determine their properties.

1. Burn TestFibers burn

differently, produce different odors when burned, and have different ash/residue appearances

2. Thermal DecompositionWhen fibers are

gently heated, they often break down/ decompose into their simpler units

3. Chemical TestsSolubility and

chemical decomposition properties are different based on fabrics are made of.

4. Microscopic ExaminationGetting a closer look

at a fiber under a microscope to determine it’s properties

FIBER LABTake 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?