Forensic Medicine: Hair and Fiber Identification PDF

The Bright right series.. In practical forensic medicine.. ‹.. Identification of hair and fibers.. › Section 1 Channel name : @brightright4th  Identification of hair and f...

The Bright right series.. In practical forensic medicine.. ‹.. Identification of hair and fibers.. › Section 1 Channel name : @brightright4th  Identification of hair and fibers There are three parts of hair: 1. The hair is the part of the hair that is exposed at the 1.Hair:‫الجزء ده مش كل الدكاتره بتشرحه هو قرايه تمهيد للسكشن وفي الكتاب‬ shaft skin’s surface. It ends with the hair tip. Intro: Hair is commonly encountered in almost all criminal 2. The hair 1). is the rest of the hair, which is anchored cases, It can be found on anywhere at the crime scene. root in the follicle, lies below the surface of the skin. Forensic hair a scientific method of analyzing trace 2).It ends deep in the dermis at the hair bulb, analysis evidence from a crime scene. and includes a layer of mitotically active Importance Forensic analysis of hair or fibers reveals basal cells. many facts that will provide investigators 3).The hair bulb surrounds the hair papilla, with important information for potential which is made of connective tissue and leads. contains blood capillaries and nerve endings from the dermis. Origin and structure of hair: 4).Two sheaths, an inner and outer sheath, surround the follicle. Hair 1). Human hair consists of proteins, water 5).The inner sheath follows the hair shaft component and ends below the opening of a sebaceous and lipids. (oil) gland. The outer sheath continues all the 2).It is a keratinous filament growing out of way up to the gland. the epidermis. 6).A muscle called an erector pili muscle attaches below the gland to a fibrous layer 3).It is primarily made of dead, keratinized around the outer sheath. cells. When this muscle contracts, it causes the hair to stand up which also causes the sebaceous Hair follicle Strands of hair originate in an epidermal gland to secrete oil. penetration of the dermis. Channel username : @ brightright4th 1 Growth cycle of hair: there are 3 phases of growth Type of hair examination : 1). Physical examination 1.Anagen ithe active phase of the hair ,The cells in the 2). Chemical examination 3). Microscopical examination root of the hair are dividing rapidly and it took Physical Examination of hair 2-6 years , hair follicle in this stage healthy and cup shape. 1.examination of hair color 2.Catagen a transitional stage. Hair growth slows and - In humans, natural color of hair depends on the race the outer root sheath shrinks and attaches to African race has black hair, while European race has hair the root of the hair. it took 1-2 weeks color graduated from grey to blond. 3.Telogen the resting phase during this phase, the hair follicle is completely at rest and hair is shed - In animals, natural color of hair differs among individuals from the scalp. in the same species. About 25 to 100 telogen hairs are shed Moreover, the color of hair varies among body parts in the normally each day. no growth of hair it took 5-8 weeks , the hair same individual. follicle is atrophied and thin Hair dyeing: The color of hair can be masked with artificial Questions asked in forensic lab? dyes. Some of these dyes can be removed via washing with 1).Hair of fibers ? water but other dyes, like permanent ones, cannot be 2). If fibers which kind of it ? washed, thus you can determine the original color of hair via 3). If hair animal or human , if animal ? root and scalp examination. 4). Which animal species , race ? 4). Which part of body , natural of artificial colors ? Characters of dyed hair : color is not uniform, roots have 5). Male or female ? different color, hair is without luster, scalp skin is also Examination of hair ‫بداية المهم‬ colored and hair. Channel username : @ brightright4th 2 from other body parts has different color. It varies among body parts for each individual. Tail hair is Some people stain their own hair or the hair of their pets or thicker than that from other parts of the body other animals making it darker or lighter. 5. Number of hair: Dark hair can be lightened by hydrogen peroxide. This means number of hairs that collected from the crime scene and sent to the lab. While light hair may be darkened by bismuth or silver 6. Debris attached to hair: compound. Hair may be tinged with a foreign material like mucus, How can you differentiate between natural and blood, fecal matter, semen, etc. artificial hair ? It can give idea about the site of hair. 1). By naked eyes 2). By microscope 2.Form of hair 2.Chemical Examination of hair It vary according to race: 1. Burn test: Differentiate between hair and fiber. 1.Monogoloids : Asian people they have straight hair and in ‫مهم‬ If you expose hair to a direct flame , hair cross section the hair is round. will resist burn. It will round to its axis and give 2.Caucasian : in Europe and north Africa and western Asia characteristic burnt-feather like odor they have wavy hair and the hair have oval to round shape in (singed hair). cross section. While fibers will burn easily. Fiber not give any of this character. 3.Negroids : Africa they have coiled or spiral(frizzy hair) 2. Alcoholic The sample (hair or fibers) + few drops of hair shape the hair is kidney or elliptical in cross section. alpha- Distal water. 3. Length of hair naphthol Water + H2SO4 + Alcoholic α-naphthol → It varies from species to other and among body parts for test: Violet color (in case of fibers). each individual ,Tail hair is longer than that in other parts of 3.Microscopic Examination of hair the body. Female hair is taller than male hair. 4. Breadth of hair Channel username : @ brightright4th 3  Preparation of hair sample : Procedure 1). Put the sample (hair or fiber) in a petri-dish ‫كبر دماغك‬ contains equal amounts of ethyl alcohol and diethyl ether for 10 min. 2).Turn the sample from time to time. Then, 2.Cortex: transfer the sample to a petri-dish contains The middle layer of the hair between the cuticle and the xylene for 10 min (turning from time to time). medulla. 3).Dry the sample on a filter paper, then place It is made of spindle shaped cells and pigment granules which the sample on a clean and dry glass slide. give color to the hair. 4).Use Canada balsam as a mounting medium 3.Medulla:‫اقدر اتعرف عن الشعرايه من خاللها‬ over the sample, cover with a glass cover and The innermost layer of the hair , It is made of cells and has dry in a hot air oven at 70⁰C for 24h. different patterns. Then examine under light microscope. Patterns of medulla : Microscopic structure of hair : Continuous, fragmented (interrupted) and absent 1.Cuticle (scales): The cuticle: is a translucent outer layer of the hair shaft and consists of a series of overlapping scales that have different patterns. The outermost layer of the hair , It is made of keratin Difference between Human and animal hair and resists chemical decomposition. Basic patterns of cuticle /scales: criteria Human hair Animal hair 1). Imbricated (flattened) in human hairs and many animal cuticle Regular , formed from one Irregular ,formed hairs. cell layer from more than ‫ بيقا شكلها منتظم وبتتكون من صف واحد من‬one cell layer 2).Coronal (crown-like) in hairs of small rodents and bats. ‫الخاليا‬ ‫شكلها مش منتظم وبتتكون‬ 3). Spinous (petal-like) in mink hairs and on the fur hairs of ‫من اكتر من صف خاليا‬ seals, cats, and some other animals. Channel username : @ brightright4th 4 cortex Broad without cross Narrow with Cotton a natural plant fiber, it is a tape-like, flattened striation cross striation fiber and has a spiral form ‫بيكون عريض‬ ‫بيكون حجمه مش كبير‬ ‫القطن‬ ‫وبتكون ملفوفه ع نفسها‬DNA ‫الياف من اصل نباتي بتبقا شبه شريط ال‬ medulla Thin(interrupted may be Thick , absent) continuous ‫بنكون رفيعه وممكن تكون مش موجوده‬ ‫بتكون سميكه‬ Medullary Less than 0.3 More than 0.5 index (MI) Silk a natural animal fiber, it is cylindrical, regular, Medullary index(MI) : fiber‫ حرير‬without swelling or twisting, it has well-defined boundary, and is refractive to light. Uses of used to differentiate between human and animal ‫شكله مش منتظم وكمان بيعكس الضوء وحدوده متحدده ومن اصل حيواني‬ MI hair. ‫من الحاجات المهمه ال بنستخدمها فالتميز بين شعر االنسان والحيوان‬ formula MI= Diameter of medulla / diameter of hair shaft Normal 1).MI of human hair :