Handling and Preservation of Biological Evidence -hair and fiber.pptx

Criminology notes

1. Handling and Preservation of Biological Trace Evidence: Hair & Fiber Compiled by Engr. Aida A. Duarte

2. Learning Objectives At the end of this lesson, the student will be able to : Learn about: Handling Collecting Preserving Transporting Of hair and fiber as evidence.

3. Introduction Note: CTTO Hair and fiber evidence plays a significant role in forensic science due to their ability to link individuals to crime scenes, objects, or other individuals. Handling, collecting, preserving, and transporting them is crucial for the investigation.

4. Handling Note: CTTO Minimize Contamination: Always wear gloves to avoid contaminating the evidence with your own hair or fibers. Use Proper Tools: Use clean, non-metallic tools like tweezers or forceps to handle the hair and fibers. Metal tools can sometimes introduce contamination or damage the evidence . Avoid Physical Contact: Handle evidence as little as possible to reduce the risk of contamination or loss

5. Collecting Note: CTTO Hair Evidence: From the Scene: Use clean tweezers to carefully pick up individual hairs. If hairs are found on surfaces like clothing or furniture, use a clean brush or tape to lift them. From a Victim or Suspect: If collecting hair directly from a person, ensure that the collection is done with proper consent and using sterile equipment . Collecting Multiple Samples: If needed, collect multiple samples from various areas of the body to ensure a comprehensive sample.

6. Collecting Note: CTTO Fiber Evidence: From the Surfaces: Use clean, sticky tape or a lint roller to lift fibers from surfaces. Place the tape or roller directly onto a piece of clean paper or a plastic bag From Clothing: Carefully cut and collect sections of clothing or fabric where fibers are suspected to be present. Avoid shaking or disturbing the item too much.

7. Preserving Note: CTTO Packaging: Hair: Place hair samples in small, clean, and breathable paper or envelopes or pill box. Avoid using plastic bags as they can cause moisture buildup, which may deteriorate the sample. Fibers: Place fiber samples in clean, labeled paper or plastic bags. Ensure that the fibers are not disturbed or compressed.

8. Preserving Note: CTTO Labeling: Clearly label all evidence with details such as the location, date, and any other pertinent information. This helps maintain the chain custody and ensures that the evidence is correctly identified. Storage: Store evidence in a cool, dry place to prevent degradation. Avoid exposure to direct sunlight, heat, or moisture.

9. Transporting Note: CTTO Secure packaging : Ensure that evidence is securely packaged to prevent any loss or contamination during transportation. Use tamper-evident seals if possible. Chain of Custody : Maintain a detailed chain of custody log that records every person who handles the evidence, the date and time, and the purpose of handling. This is critical for maintaining the integrity of the evidence.

10. Transporting Note: CTTO Transport Condition : Transport evidence in a way that avoids physical damage or contamination. If necessary, use appropriate environmental controls, such as temperature, regulation, to preserve the evidence. Following these guidelines will help ensure that hair and fiber evidence remains as intact and uncontaminated as possible, which is essential for accurate forensic analysis.

11. Biology of Hair Note: CTTO Composed of the protein Keratin (primary component of finger and toe nails) Produced from the hair follicle (develop during fetal development and none are produced after birth) Color is due to pigments, or chemical compounds that reflect certain wavelength of visible light

12. Biology of Hair Note: CTTO Shape and texture is influenced by genes, but physical appearance can be affected by nutrition and intentional alteration (curling, perms, etc.) Area from which a hair originated can be determined by the sample’s length, shape, size and color In order to have DNA, the root must be present

13. Biology of Hair Note: CTTO Parts of the hair: a. Cuticle – varies in scales, thickness, and presence of pigment. Can be used to distinguish hairs of different species but not useful in distinguishing between people. There are three basic patterns: coronal, spinous and imbricate.

14. Biology of Hair Note: CTTO Parts of the hair: b. Cortex – varies in thickness, texture and color. The distribution of the cortex is the most important component in determining from which individual a human hair may have come. Microscopic examination can reveal condition and shape of the root and tip.

15. Biology of Hair Note: CTTO Parts of the hair: c. Medulla – varies in thickness, broken or not, and opacity (amount of light that goes through). Sometimes it is absent in some species. Like the cuticle, the medulla is useful in distinguishing between hairs of different species, but often is not much in differentiating between hairs from different people.

16. Biology of Hair Note: CTTO The root of the hair: Contains the DNA May look different based on whether or not it has been pulled out or it just fell out.

17. Hair Note: CTTO

18. Fiber Note: CTTO Smallest unit of a textile material that has a length many times greater than its diameter Can be spun with other fibers to form a yarn Matching unique fibers on a victim would be helpful, while common fibers are not as helpful Cross transfers between a suspect and victim dramatically increases the likelihood that physical contact occurred

19. Fiber : Natural Note: CTTO Fibers that come from plants or animals ex. Silk, cotton, cashmere, wool, etc. Cotton is the most commonly used plant fibers in textiles. Wool is the most commonly used animal fiber in textiles (from sheep). cotton wool

20. Fiber : Synthetic Note: CTTO Fibers that are man-made from altered natural sources . Ex. Nylon, rayon, polyester, spandex, etc. More than half of all fibers used in textile production. nylon polyester

21. Fiber: Natural Vs Synthetic Note: CTTO What difference can be observed between natural and synthetic fibers? cotton rayon

22. Fiber Note: CTTO How to differentiate fibers? Microscopic observation Burning ( odor, how it burns, residue Thermal decomposition (gently heating) Chemical tests (solubility and decomposition) Dye analysis Density

23. Types of Fibers Note: CTTO