Do Now:
1. Name 2 ways to determine the sex of a skeleton.
2. How does your hair differ from the person to the left or right of you?
3. Get out your brochure.
Objective: SWBAT explain the various parts of a hair
Announcements
Grades:
Gloves: (optional)
Strand: yours and animal
Parts of the HairCuticle- tough, clear
outside covering for protection
Cortex- middle layer that provides strength and gives hair its color
Medulla- interior that provides flexibility
Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.hairdressersus.com/micro/Image5b.jpg
Hair Structure
Cuticle•Scales•Varies with species•Cuticles in human look the same
Cortex
•Texture• Color
• Protein Keratin – strength
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…..?
MedullaThe medulla may vary in:
• Continuity - one continuous structure or broken into pieces
• Varies with species • Varies with different races
• It may also be absent in some species.
http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair
Hair Structure
http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg
The MedullaMost humans have no medulla (except Native Americans and
Asians, where medulla is usually continuous)
Types:InterruptedFragmentedContinuousStackedAbsent—not present
Recruitment Project1. Set up
2. Name and Case Number
3. Recruitment Grade (20) 15 pts
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 TransferPrimary 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?
