TEACHER INSTRUCTIONS

Goals
1. Introduce students to the thought process involved in developing a technique for forensic analysis.
2. Introduce students to the physical structure of hair.
3. Provide opportunity for students to improve skills in observation, critical thinking, and microscopy.

This activity involves two parts, which may be performed separately or as a cohesive unit. The first part requires students to examine a set of hairs. Using their observational and critical thinking skills, they will develop a procedure to identify hairs collected from crime scenes.

The second part is intended to complement any of the crime scene scenarios developed by the UCB Hughes Initiative. In this part, students examine the hairs supposedly collected from the crime scene as well as hairs from suspects and
their pets. They will use the data sheet provided to determine which suspect is the most likely match. If you intend to use both parts, it is recommended that you do them in the order described above.

Hair Analysis Activity - Part One

Materials
- Hairs from different species and individuals (humans, cats, dogs, horse, deer, rabbit, guinea pig, chinchilla, etc)
- Microscope slides
- Cover slips
- Water and droppers
- Microscopes

Instructions
Prepare a set of labeled, wet-mount slides for each group of 2-4 students. Smaller groups are probably better, but do whatever works best for your classroom. Each set should contain one slide with hairs or a single hair from each individual. Eight to ten slides total per set is a good number. A hypothetical set might include the following slides:

1.) human hair (red, long, curly)
2.) dog hair (black, straight)
3.) cat hair (grey, long)
4.) deer hair
5.) dog hair (white, wiry)
6.) cat hair (beige, short)
7.) human hair (brown, straight, short)
8.) rabbit hair
9.) human hair (blonde, wavy, long)
10.) horse hair

Instead of preparing the slides yourself, you may choose to give each team of students a set of labeled envelopes containing the hairs and ask them to prepare the wet mounts.

Instructions for preparing wet mounts of hair are included in the student handout for Part Two.

Hair Analysis Activity - Part Two
Materials
- Hairs from four different humans, one dog and one cat
- Microscope slides
- Cover slips
- Water and droppers
- Microscopes

Instructions
Prepare a set of four envelopes, labeled and filled according to specifications listed below for each team of students. Ideally, envelopes A, B, and D should contain an individual paper packet for each individual that the hair is collected
from. Each individual packet should ideally contain about 20 hairs. Some volunteers may be more amenable than others to donating this much hair.

In addition to the set of envelopes, provide each team of students with slides, coverslips, water and droppers, microscope, and copies of the student handout. Each team will need 8 copies (one per hair) of the data collection sheet.

----------------------------------------------------------------------------------------------------------------------------------------------------------

STUDENT INSTRUCTIONS

What would you do if you were given a collection of hairs from a crime scene and asked to determine if any of them came from the prime suspect? What characteristics of the hairs would you examine to look for differences and similarities?

Complete the following activity to help you decide how you would distinguish between hairs. At the end you will be asked to list the criteria that you would use to establish identity. There are two basic types of criteria: objective criteria (those which can be measured in units not dependent on personal judgement by the observer such as length, width, light absorbance, etc.) and subjective criteria (those which are dependent on observer judgement such as colour, texture, and shape).

Which type of criteria do think would be more reliable and more convincing? Why?

The following explanation of the physical structure of hair may be particularly useful as you examine the hairs.
Hair is composed of three principal parts:

Cuticle – outer coating composed of overlapping scales.
Medulla – central core, which may be absent.
Cortex – protein-rich structure surrounding the medulla; contains pigment.

Examine the set of labeled slides provided to you under a microscope. View each sample at both low and high power. Locate the three primary structures of each hair. As you examine the hairs, think about how they differ from one another and how you would use the differing characteristics to establish identity.

Fill in the table below and answer the following questions:

1.) How does the cuticle differ among hairs of different species? Different individuals of the same species? Try to list both objective and subjective criteria for differentiating the cuticle of different species.

2.) How does the cortex differ among hairs of different species? Different individuals of the same species? Try to list both objective and subjective criteria for differentiating the cortex of different species.

3.) How does the medulla differ among hairs of different species? Different individuals of the same species? Try to list both objective and subjective criteria for differentiating the medulla of different species.

4.) Are there other characteristics of the hairs that differ between species or individuals? List at least three. Would the criteria based on these characteristics be objective or subjective?

----------------------------------------------------------------------------------------------------------------------------------------------------------

This activity was inspired by a similar activity described in the book Crime Scene Investigations by Pam Walker and Elaine Wood, Center for Applied Research in Education, 1998.

You have been given four envelopes containing hairs from each suspect’s body and clothing as well as hairs found at the crime scene. The envelopes with hairs from the suspects are labeled with letters only (suspect A, suspect B, and
suspect C), so that you do not know the identity of the contents. The envelope with hairs from the crime scene is labeled evidence.

Your job is to examine the samples in each envelope and compare them. If any of the samples match, it could link one of the suspects to the crime scene. Follow the steps below to complete your analysis. You may wish to split up the work within your team by having one person analyze the evidence envelope, one person envelope A, etc.

1.) Label a set of slides for each envelope with the envelope’s letter and the packet number (if there is more than one packet per envelope). The number of packets contained within the envelope will be written on the outside. You must examine each packet.

2.) Open envelope A. Open the first packet and remove one or two hairs.
3.) Measure the length of the hair in millimeters.
4.) Make a wet mount of each hair using your labeled slides.

a.) Place a small drop of water on the center of the slide.
b.) Place the appropriate hair in the drop of water so that the hair lies flat on the slide. Cut a small (1 cm) length of hair if necessary.
c.) Cover the hair and water drop with a cover slip.

5.) Examine each slide under the microscope at high power. Fill out the data sheet on each hair. You may add criteria of your own to the data sheet in the blanks provided. Refer to the handout on hair identification for help with terms.
6.) Repeat steps 2-4 with the remaining packets in each of the envelopes.
7.) Compare data sheets. Are there any packets containing hairs that appear to match hairs from the evidence envelope? Which ones? Why would you say they are a match?

Think about what an apparent match would mean in terms of evidence. How would you report your results to the district attorney or to a jury?

Hair analysis data

Label:_______________ Date:______________________________

Guide to Identification

Unfortunately, hair is not the best type of physical evidence for establishing identity. It is not possible to show with any certainty that two hairs came from the same person or animal. However, hair can be used to rule out certain suspects or scenarios. It can also be used to corroborate (support) other physical evidence if it is consistent with the rest of the evidence.How is hair analyzed?

The simplest method of identification is visual observation with the naked eye, which can indicate colour, length, and amount of curl. Hair can also be examined microscopically to reveal characteristics of its physical structure. Hair is composed of three principal parts:

Cuticle – outer coating composed of overlapping scales.
Medulla – central core, which may be absent.
Cortex – protein-rich structure surrounding the medulla; contains pigment.

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.

Cuticle: The scales of the cuticle may vary in how many there are per unit of measure, how much they overlap, their overall shape, and how much they protrude from the surface. The thickness of the cuticle may vary as well, and the
cuticles of some species' hairs may contain pigment. Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people.

Medulla: The medulla may vary in thickness, continuity (one continuous structure or broken into pieces), and opacity (how much light is able to pass through it). It may also be absent. 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.

Cortex: The cortex varies in thickness, texture, and colour and distribution of pigments. 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.

Biology of Hair

Hair is an outgrowth of the skin and is produced from a structure called the hair follicle. Humans develop hair follicles during fetal development, and no new follicles are produced after birth. Hair is composed of the protein keratin. Keratin is also the primary component of finger and toe nails.

Hair colour is mostly the result of pigments -- chemical compounds which reflect certain wavelengths of visible light. There are two main pigments found in human hair: eumelanin, which gives colour to brown or black hair and pheomelanin, which produces the colour in blonde or red hair. Hair colour may also be influenced by the optical effects of light reflecting and bouncing off the surfaces of the different hair layers.

Hair shape (round or oval cross-section) and texture (curly or straight) is influenced heavily by genes. However, nutritional status and intentional alteration (heat curling, "perms") can affect the physical appearance of hair.

Literature Cited:
- Fundamentals of Criminal Investigation. Charles O’Hara and Gregory O’Hara. Charles C. Thomas publisher. 1994
- The Basics of Hair. Ridgewood Dermatology & Hair Transplant Center, PC, 190 Dayton St.,Ridgewood, NJ 07450
- Crime Scene Investigations . Pam Walker and Elaine Wood. Center for Applied Research in Education -- publisher. 1998.
- Crime Scene to Court: The Essentials of Forensic Science. Peter White (ed.) The Royal Sciety of Chemistry publisher. 1998.