Science with Reed · Web viewHair strands found at a crime scene can often provide clues for investigators. Although hair analysis cannot pinpoint a suspect with 100% certainty, it

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The Integumentary System: Fingerprints and HairWarm UpObjective: Scientists will describe the integumentary system by analyzing fingerprints and hair.

1. What is the topic?

2. What will you be doing?

3. Why is this important?

4. How will you know if you have done well?

FINGERPRINTS

BackgroundFingerprinting has been used as a tool to help solve crimes since the 19th century. Because no two people have the same fingerprints (not even identical twins), a fingerprint found at a crime scene is a useful way to match a suspect with the crime scene. Fingerprints are the tiny raised spiral and concentric patterns called ridges found on the tip of each finger. Fingerprints form before you are even born and remain unchanged during a person’s lifetime. They form from the pressure on the fingers from the baby touching their surroundings. All of the ridges of fingerprints form patterns called loops, whorls, and arches. Every finger has a unique fingerprint.

Arch: Loop Whorl

Create your own fingerprint in the space provided below:Your Fingerprint What type of ridge pattern does your finger

show?

How do you know?

HAIRBackground

Hair strands found at a crime scene can often provide clues for investigators. Although hair analysis cannot pinpoint a suspect with 100% certainty, it can help eliminate persons of interest and provide clues as to who might have been present at the scene of a crime. At the microscopic level, hair can provide information about owner’s characteristics such as race, sex, and possibly age. Hair is composed of a protein called keratin. Keratin is the same protein that forms our nails and our outer layer of skin. Hair shafts are composed of three layers: the cuticle, the cortex, and the medulla. The cuticle is the outermost layer of the hair. When comparing hair samples, there are a number of microscopic characteristics associated with the cuticle, such as the thickness of the cuticle, the variation in the thickness, the presence of pigment, and the color. Also, the nature of the outer cuticle margin may be smooth, looped, ragged, or damaged. The cuticle covers the intermediate layer, called the cortex. The cortex is home to the pigment-containing granules responsible for hair color and contains many of the characteristics used in the microscopic analysis of hair. The organization, density, size, and distribution of the pigment granules vary greatly between racial groups, individuals, and even to a small extent within an individual. Finally, the innermost layer of hair is called the medulla. This layer may be continuous, discontinuous, fragmentary, or even absent. The diameter of the medulla is a useful characteristic in the identification and comparison process. In addition to the three anatomical regions of the hair, many other characteristics are useful in the microscopic comparison process, including: the growth stage of the hair, the diameter of the hair, presence of artificial treatment, any damage present, and any diseases and other hair abnormalities.

Pull a strand of your hair. Examine it with the hand lens and microscope. Draw what you see below and LABEL the medulla, cuticle, and cortex.

Review the evidence. Who’s fingerprints and hair were at the crime scene? Explain how you know.

Evidence

Hair Found at Crime Scene: Alex Garcia:

Doug Greene: Erica Piedmont:

Lucy Leffingwell: Anna Garcia:

When experts compare two fingerprints, they look at the arrangement, shape, size, and number of lines in the fingerprint patterns to distinguish one from another. They also analyze very tiny characteristics called minutiae, tiny fingerprint ridge details and make sure to match at least 12-15 points of similarity between the two prints to establish that they are identical. When two fingerprints show similarities with at least 12 minutiae, it is called a 12 Point Match, something you may have heard on your favorite crime scene show. Below are the ten most frequent minutiae, with the ending ridge being the most frequent and the triple fork being the least frequent.

Evidence A fingerprint was found at the scene of the crime that is thought to be suspicious. The police have obtained fingerprints from all of the persons of interest. It is your job to determine whether any of their fingerprints match the fingerprint found at the scene of the crime. To do this, you will need to identify the ridge pattern category (arch, loop, or whorl) and identify 10 minutiae of the fingerprint obtained at the crime scene. Using this information, you will then compare the fingerprint to those of the persons of interest to see if anyone matches. You may use a magnifying glass. You will also have to identify the ridge pattern for each person of interest.

Fingerprint from Crime Scene:

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Fingerprint from Crime Scene:

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Erica Piedmont:

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Alex Garcia:

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Lucy Leffingwell:

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Doug Greene: Anna Garcia:

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