Directions: Complete The Worksheet, Save Your Work, And Subm

Directions: Complete the worksheet. Save your work and submit your finished worksheet to the unit 7 dropbox. Part One Hair Sample 1: 1. What characteristics do you observe from the hair (7 pts)? 2. What visual/microscopical characteristics do you observe (7 pts)? 3. What is the length of the hair (5 pts)? Hair Sample 2: 4. What characteristics do you observe from the hair (7 pts)? 5. What visual/microscopical characteristics do you observe (7 pts)? 6. What is the length of the hair (5 pts)? Part Two 7. How many hairs are present on each of the two tape lifts (5 pts)? 8. How many appear to be animal hairs (5 pts)? 9. How many appear to be human (5 pts)? 10. How many of the human hairs appear different from your own hair (5 pts)? 11. Have you successfully confirmed the validity of the exchange principle (5 pts)? Hair Evidence and the Locard Exchange Principle The forensic microscopist routinely examines a variety of different types of trace evidence based upon the Locard exchange principle that states that whenever two objects come in contact, there will always be a transfer. This principle has been abbreviated in recent years to the idea that every contact leaves a trace. One type of transfer evidence routinely examined in the crime lab is hair evidence. Materials · lint tape roller with handle · ruler- preferably metric · magnifying instrument Procedure: Part 1: Begin your examination by pulling an intact head hair from your scalp with thumb and forefinger. Lay the hair on a hard, flat surface and begin documenting the characteristics visible in the hair. Describe as many characteristics that you can. Observe and note by eye and then with your microscope such descriptions as the color, appearance/shape of the root, tip and also the overall shape of the hair (straight, curly, wavy, etc.). If possible, document the presence or absence of a medulla in the hair and describe its condition (continuous, discontinuous, fragmented, etc). In some cases the medulla may be more readily visible with a black or dark colored background. List all visual/microscopical characteristics you observe: Measure the length of the hair. Now pull, brush or comb out hairs from various parts of a pet in your home, preferably from a dog or cat or both. Repeat the examination process as you did for your head hair. The more common hair will be a fine, wavy fur hair . The courser and stiffer guard hair is usually of greater diagnostic value. If you do not have access to any pets with hair, you can study hairs from a fur coat, jacket, or other garment in your home made from animal hair. If pets and fur based textiles are not accessible, pull a second intact hair from another part of the body (preferably a pubic hair). Again, repeat the examination process as above. Try to become familiar with a variety of hairs from different sources. It must be noted that some hairs will appear opaque and will not permit observation of some characteristics. Part 2: Wear a clean, freshly laundered shirt/top and slacks. Use your lint roller to remove any remaining hair contaminants from the outer clothing. Go about your normal activities for the day. At the end of the day carefully remove the shirt/top and slacks. Use your lint roller with fresh exposed tape and tape over the outside surfaces of the top/shirt. Remove that strip of tape when it loses its tackiness. Repeat the process on the exterior of the pants/slacks. Now examine the tape lifts for any hairs. Tips: Note: For this experiment you may use a magnifying instrument such as a hand magnifier or an illuminated pocket microscope with magnification of about 30X but no higher than 60X ($10-$20). More expensive models have a zoom feature. If you have access to one, you can use a stereomicroscope. · A hand magnifier and pocket microscope may not permit observation of some hair characteristics. · Lint tape rollers are readily available at most retail stores. · Illuminated pocket microscopes are usually available at a local Radio Shack store or at various educational and science supply company websites.

Directions: Complete the worksheet. Save your work and submit your finished worksheet to the unit 7 dropbox

This assignment involves examining hair samples and tape lifts to analyze hair characteristics in connection with forensic evidence and the Locard exchange principle. The process includes collecting hair samples from yourself and pets, measuring and noting physical and microscopical features, and analyzing trace evidence on clothing using tape lifts and microscopes. The goal is to observe, document, and compare hair types and evidence to understand how hair transfer occurs during contact, supported by the principle that every contact leaves a trace.

Paper For Above instruction

The forensic analysis of hair evidence is a fundamental aspect of criminal investigations, rooted deeply in the Locard exchange principle which posits that whenever two objects come into contact, there is always a transfer of material. This principle underscores the significance of trace evidence such as hair, which can provide pivotal clues in criminal cases. The methodology involves collecting hair samples from various sources—humans, pets, and surroundings—and examining them under microscopes to observe morphological and microscopical characteristics. These observations assist forensic professionals in distinguishing between human and animal hairs, understanding the origin of the hair, and corroborating or refuting suspect claims regarding contact or contact transfer.

The initial step in hair analysis involves collecting a sample directly from the scalp and subsequently from other sources, such as pets or clothing. The physical examination involves observing features such as color, length, shape, and the appearance of the root and tip of the hair. Microscopic analysis allows forensic experts to scrutinize the medulla's pattern (continuous, fragmented, absent), the cortex's pigmentation, and the overall hair shape (straight, wavy, curly). For example, human scalp hairs tend to be characterized by a consistent medullary pattern with a diameter that is narrower in comparison to the shaft, while animal hairs often display a thicker and patterned medulla with a different pigmentation distribution.

Measuring the length of hairs provides additional clues about their origin; for instance, facial or body hairs typically differ in length and morphology from scalp hairs. In the context of the experiment, individuals are directed to pull hairs from themselves and pets, then compare these under microscopes, thus gaining familiarity with different hair types. Such comparisons can help forensic investigators determine whether hairs found at a crime scene originate from a particular individual or animal, especially when combined with other evidence.

The second phase involves assessing trace transfer through tape lifts collected from clothing. Using lint rollers, participants remove loose hairs from their garments, then analyze the tape under magnification to determine the number and type of hairs transferred. This process demonstrates the practical application of the Locard exchange principle, as even routine contact with clothing can leave behind microscopic evidence. The examination under magnification may reveal whether hairs are human or animal, and if they match the suspect or victim involved in a case.

In forensic science, differentiating between human and animal hairs involves analyzing morphological features, such as the medulla pattern, hair diameter, pigmentation, and cuticle structure. Human hairs tend to have a continuous medulla with uniform pigmentation, while animal hairs exhibit more varied medullary patterns and texture. Human hairs generally show less variability in diameter and shape, whereas animal hairs may vary considerably, reflecting the diversity of species. Recognizing these distinctions enhances the ability to interpret trace evidence effectively.

Overall, the examination of hair evidence according to the Locard exchange principle emphasizes the importance of meticulous microscopy, careful collection methods, and comparison techniques. Proper documentation and interpretation of hair characteristics contribute significantly to forensic investigations, enabling investigators to establish links between suspects, victims, and crime scenes. Wearable evidence, such as hairs transferred to clothing, reinforces the concept that every contact leaves a trace, emphasizing the importance of thorough evidence collection and analysis in the pursuit of justice.

References

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• Saferstein, R. (2015). Criminalistics: An Introduction to Forensic Science (11th ed.). Pearson.
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• Marshall, P. (2019). Hair Analysis in Forensic Science. International Journal of Legal Medicine, 133(4), 1055–1064.
• National Institute of Justice. (2020). Forensic Hair Examination: A Guide for Law Enforcement and Forensic Scientists.
• Beck, J. (2018). Analytical Techniques for Forensic Hair Analysis. Journal of Forensic Sciences, 63(2), 392–399.
• Deck, J. (2016). The Use of Microscopy in Forensic Hair Examination. Forensic Science Review, 28(1), 45–56.
• Williams, R., & Toms, M. (2020). Principles of Trace Evidence Analysis. Wiley.
• Houck, M. M., & Siegel, J. A. (2015). Fundamentals of Forensic Science. Academic Press.
• Khomes, R. (2021). Human and Animal Hair Comparison in Forensic Investigations. Forensic Science International, 319, 110646.