Hair Lab #1- 50 points
Name:___________________________
Due:
Hair Lab 1: Examination of Hair by Microscopy
Note: all sketches should be done in color!
INTRODUCTION
Hair is a common form of evidence in many cases of homicide, as well as in crimes of sexual assault. It also enters into many
cases of burglary. Some of the points that may be proven by the use of hair as physical evidence are as follows:
1.
It can link a suspect to the scene of the crime.
2.
It can indicate the entrance or exit route of the criminal.
3.
It can show contact with the victim.
4.
It can serve to identify clothes or shoes, abandoned or denied, by the suspect.
5.
It can indicate the contact of a victim in a hit-and-run accident with the car of the suspect.
Sometimes the contact itself is not in doubt, but the exact part of the car where the victim was hit plays an important role in the
evaluation of the dynamic features of the case.
Hair from any part of the body exhibits a range of characteristics, such as color, length, and diameter. Even hair from different
parts of the area (the crown, sides and rear of the head, for example), will differ somewhat. It is, therefore, necessary for the forensic
investigator to keep this in mind when collecting reference hairs and to obtain an adequate supply to compare with the suspect’s hair.
Usually, the collection of several dozen hairs from relevant parts of the body will suffice.
The parts of the hair that are easily seen by use of a microscope under magnification are the medulla, cortex and the cuticle.
Many animal hairs are easily distinguished from human hairs by the size and shape of their medullae and the patterns of their cuticle
or scale structure.
Part I: Define the following:
Cuticle:
Scales:
Sketch and label the 6 scale types:
1.
2.
3.
4.
5.
6.
Cortex:
Cortical fusi:
Medulla:
1
Hair Lab #1- 50 points
Name:___________________________
Due:
Sketch and label the 5 medulla patterns:
Name the 5 medulla types:
1.
1.
2.
2.
3.
3.
4.
4.
5.
5.
Part II: Human Hair Comparison:
1. Pull (do not cut) 4 strands of hair from your own head
2. On a piece of notebook paper, lay out your hair sample. Pull the hair until it is taut (no slack) and measure its
length in centimeters. Average your 4 hairs and record the average length here:______________ cm
3. After cleaning it with alcohol, place one of your hair samples on a glass slide and give one sample to each of the
people in your lab group. Observe your hair and that of the other people in your group (make sure each of them
has been cleaned with ethanol.). Record your results in a Part II Data Table
4. Following is a very informal way of determining the diameter of a piece of hair. Begin by visually
“guesstimating” how many of the hairs it will take to fill the field of view of the microscope. To do this, you have
to imagine how many of these hairs would fill the field of view if you laid them side-by-side? Could you fir 4?
10? 25?
5. For the microscopes used in this class, determine the hair diameter by using the following formula:
Hair
Diameter
=
Diameter of the high power field of view (500 micrometers)
# of hairs you could fit in the field of view at high power (400X)
The medullar index is determined by measuring the diameter of the medulla and dividing it by the diameter of the hair.
This fraction is used in cases to help match hair samples. More practically, I would like you to “eyeball” the medulla
index.
This number should be a fraction. If it is less than 1/3, what is the organism? ___________________
If it is greater than ½, what is the organism? __________________
Therefore, are you a human? ________________
2
Hair Lab #1- 50 points
Name:___________________________
Due:
PART III: CRIME SCENE
Three persons are in an automobile involved in a one-car accident. Some property damage is sustained, and the car is
badly damaged. This accident takes place in the evening with no witnesses present. The three persons in the automobile
are only slightly bruised, none of them sustaining any serious injuries. All the people do, however, suffer bumps on their
heads, with some laceration of the skin and resultant bleeding. One person’s head has come in contact with the
windshield of the automobile, as evidenced by the windshield being cracked, a small amount of blood and a few strands of
hair stuck to the glass at the place of impact. This was on the driver’s side of the automobile. All of the people are
suspected of being under the influence of alcohol, and each maintains that another person was driving the automobile at
the time of the accident. The officers at the scene, in an attempt to identify the driver, collected the blood and hairs from
the impact point of the windshield. They have obtained sample hairs from each of the people involved in the accident,
and have transferred all of their materials to a forensic laboratory.
INSTRUCTIONS
The samples have been labeled “A”, “B”, “C” and “Scene”. For this part of the lab, hair should NOT be cleaned before it
is examined. The adhering dust and impurities are sometimes of more evidential value than the hair itself.
1. Obtain one of the strands of hair from the vials, making sure to note which vial your sample came from. Place it
on a glass microscope slide.
2. Add one small drop of water to the hair to hold it in place, and then place a cover slip over the hair. This is
known as a wet mount.
3. Place the slide on the stage of the microscope, adjusting the magnification to 400X.
4. Fill out a data table for this hair, making sure to sketch NEATLY, using colored pencils. Do not leave out any
information! This information goes into a Part III Data Table
5. Scan along the length of the hair body. Note any foreign particles clinging to the hair. Put this information in
your data table.
6. Is the medulla fragmented, interrupted, continuous or absent?
7. Make a detailed sketch of the medulla (if there is one), using the highest possible magnification. How much of
the hair’s width does the medulla take up? Is it ½ of the diameter of the hair? ¼? ¾? Less? More? Note this
under the “Medullar index” on your data table. If you can see any cortical fusi, please sketch these in also.
8. Note the microscopic color of the hair.
9. Measure the hair’s diameter. The DIAMETER OF THE FIELD OF VIEW divided by THE # OF HAIRS YOU
COULD FIT UNDER THAT FIELD OF VIEW = THE DIAMETER OF THE HAIR SAMPLE. Make sure to
divide it out, so you have a true number and don’t forget your units! (probably µm).
10. Scan along the length of the hair, and note the pigment distribution. Are there portions of the hair that are
different colors?
11. Finally, examine along the tip of the hair, and describe it in the space provided on your data table.
12. Return your hair sample to the proper container, and repeat this procedure with each of the other hair samples.
WHICH HAIR SAMPLE COMPARES TO THE SAMPLE COLLECTED FROM THE CRIME SCENE?
___________
PART IV: ANIMAL HAIRS
Repeat the steps from PART I to observe 4 animal hairs provided to you in class. Use the Part IV Data Table for each
hair, following the same procedure as you did for Part I.
PART V: SCALE PATTERNS
Scale patterns are of little value in human hair comparisons, but can aid in distinguishing animal hairs. You will now
attempt to examine scale patterns of human and animal hairs. The pattern of cuticle scale is useful in determining the
species origin of hair. In human hair, the scales overlap smoothly, whereas in other mammalian species they protrude in
rough, serrated form.
1. Clean a strand of human hair (from any classmate or from your own head) by pulling it through a folded tissue
moistened with alcohol.
2. Smear a glass slide with a thin layer of clear nail polish.
3
Hair Lab #1- 50 points
Name:___________________________
Due:
3. Place a strand of hair on the surface of the polish. Use the edge of a cover slip to “tap” the hair down, setting it in
the nail polish.
4. Allow the surface to become partially solidified, and then lift the hair off the slide.
5. Clean the hair using tissue and nail polish before returning it to the vial from which you obtained it.
6. Place the slide under the microscope to examine the scale patterns. Use a Part V Data Table. Record your
sketches and observations of scale patterns.
7. Repeat the above procedure for one other human hair, and then for two different animal hairs (please clean each
hair with alcohol before returning it to the vial you got it from).
8. Clean the slide with Acetone (nail polish remover) before each sample, and at the end of the exercise.
PART VI: HAIR COLOR
Obtain 3 different hair colors from your classmates, as well as one gray hair sample from the teacher.
In the Part VI Data Table, sketch the hairs under 400X magnification (using true-to-life color, of course) and listing the
similarities and differences between various colors of hair samples.
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