Anth 120 Chapters 5, 10, 13
Anth 120 Chapters 5, 10, 13 Anth 120
Minnesota State University, Mankato
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Date Created: 02/19/16
2/8/16 Chapters Ten and Thirteen Hair, Fiber, Paint and Soil Physical Evidence Evidence collected at a crime scene can often link a perpetrator to the scene through individual or class characteristics Common types of trace evidence o Hair o Fiber o Paint o Soil Hair Can provide strong corroborative evidence, but has its limitations Physical and chemical properties cannot link hair to specific individuals DNA, when present, can however, identify a hair to a specific individual Color and morphology are hair’s most distinctive characteristics Morphology o Follicle – skin organ that produces hair o Cuticle – scale structure covering the exterior of the hair Provides hair with its resistance to decomposition and its maintenance of structural features Formed by overlapping scales that point towards the hair’s end/tip Scales are keratinized Three types of scales: Coronal (stacked cups) Spinous (petal-like) Imbricate (overlapping) Patterns Not useful for individualizing human hair Can be used to make a non-human species determination (I.e. Cat or dog) o Cortex – main body of the hair shaft; contains the pigment Cells aligned in regular array parallel to length of the hair Contains the pigment granules Color, shape and distribution of the pigment granules is used for comparison of hairs o Medulla – cellular column in center of hair (not in all hair) Medullary index – diameter of medulla relative to diameter of hair shaft In many animals medulla is large relative to the diameter of the hair (>0.5) In humans, medullary index is <0.33 Presence and appearance of medulla vary between individuals and even within individuals Can be classified as continuous, interrupted, fragmented or absent Most human head hair, except for those of Asians, have absent or fragmented medullae Animals most often have continuous or interrupted Can be cylindrical or patterned Humans have cylindrical shape o Root – produces hair and continues its growth Three hair growth phases Anagen – hair actively produced; up to six years o Flame-shaped appearance at the root o Follicular tag o Best chance for getting DNA Catagen – hair grows at a decreasing rate; 2-3 weeks o Elongated appearance o The further into the cycle, the less likely the chance for DNA Telogen – growth ends; hair pushed out of follicle; 2-6 months o Club-shaped appearance o No DNA Hair Comparison o Human vs. animal Scale structure (cuticle) Medullary index Medullary shape o Human vs. human Color Length Diameter Presence or absence of medulla Distribution, shape and color of pigment granules o Significant error rates (11% in FBI study) o Microscopic comparisons are presumptive Only DNA corroboration can positively identify an individual o Hair from different parts of the body differ Scalp hair has uniform diameter and pigment distribution Pubic hairs – short, curly, variation in shaft diameter, continuous medullae Beard hairs – coarse, triangular in cross-section; blunt tips from shaving o Scalp and pubic hair are most often scrutinized by forensic scientists o Hair dye colors the cortex and cuticle o Bleach removes pigment and gives the hair a yellowish tint o Hair grows approximately 1 cm a month o Disease, deficiency, infections can also be used to individualize a hair o Caucasian hair generally wavy or straight; pigments are evenly distributed; oval to round in cross-section o African hair generally kinky; dense uneven distribution of pigments; flat to oval in cross-section o Infant hair can be identified by fine nature, short length, fine pigments and rudimentary character o Sex can only be determined by DNA from hair o Presence of follicular tissue indicates hair was pull/brushed/combed out Some forcibly removed hair may not have adhering follicular tissue Most likely to happen if it was pulled out slowly o Nuclear DNA in root or follicular tissue is the only time hair can be individualized For DNA to be recovered from root, it must be in anagen or early catagen phase Mitochondrial DNA can exclude large portions of the population o Root banding caused by postmortem decomposition Only seen in anagen/catagen phase hairs and only in segments of hair close to scalp; varies in timing with temperature (occurs early when warm) Fiber Can be commonly transferred during homicide, assault, sexual offenses, hit-and-runs, breaking-and-entering Most fibers produce class characteristics rather than individual ones Types of fibers o Natural Animal fibers – wool, mohair cashmere, camelid, fur, etc. Plant fibers – cotton, linen o Man-made Regenerated fibers – rayon, acetate Synthetic fibers – nylon, polyester, acrylic Manufactured fibers o Rayon introduced in 1911; nylon in 1939 o Most items are comprised of manufactured fibers today o Hundreds of different types o Synthetic fibers are composed of long chains of polymers Strong and stretchy Comparison of Fibers o Color and diameter o Surface features Lengthwise striations Pitting with delustering particles o Cross-sectional shape o Dye composition Visible light microspectrophotometer Chromatographic analysis o Chemical composition Polarizing microscope comparison Birefringence Infrared microspectrophotometer Collection of fiber evidence o Significance o Potential “carriers” Clothes Carpets, rugs, bedding Car seats Knife blades o Collection Do not remove fibers Place in separate paper bags Adhesive tape lifts of body Paint Most often found in hit-and-run and burglary cases Comparison between paints to establish common origin Identification as to color, make and model Composed of binder, pigments and additives Automobile paint (varies between manufactures, in which case use PDQ database) o Electrocoat primer (gray or black) o Primer surfacer (echoes the color of primer and base coat; lighter for light cars, darker for dark cars) o Base coat o Clear coat Analysis o Color o Layer analysis o Binder formulation Pyrolysis gas chromatography = pyrogram Infrared spectrophotometry o Pigments Emission spectroscopy Inductively Coupled Plasma (ICP) Neutron activation analysis X-ray diffraction X-ray spectroscopy Significance o Color, layering and infrared spectophotometry study indicated 33,000 to one odds o Architectural paint study 99.99% differentiation o PDQ database o In-house collections Collection techniques o Care must be taken not to damage paint chips o Collect reference samples close to point of impact o Scrape paint down to metal; ¼” sample Soil Any disintegrated material, natural and/or artificial, that lies on or near the earth’s surface Materials o Rocks o Minerals o Vegetation o Animal matter o Also glass, paint chips, asphalt, brick fragments, cinders, concrete, etc. Significance o Comparison – prevalence and transferability make soil useful as physical evidence Soil found on a suspect’s shoes, clothes or car can be compared to reference samples o Identification – crime scene can possibly be identified by soil found on suspect Geologists can identify soil to particular geographical region Forensic Examination o Morphological examination Color (Munsell Soil Color Chart used in Archaeology) Low-power identification of plant, animal and artificial debris o Identification of minerals Birefringence 2200 minerals; most rare; 20 common Minerals also found in man-made materials like insulation, bricks, plaster and concrete Collection and preservation o Collect at site as well as intervals within a 100 foot radius o Soil specimens should also be collect at any alibi location o Sample should only be from top layer o 1-2 tbsp in plastic vials with location marked o Do not remove soil adhering to any suspect’s items o Lumps of soil should be collected whole layering can provide further individualization 2/15/16 Chapter Five Forensic Anthropology Forensic Anthropology – the field of study involving the analysis of human skeletal remains resulting from unexplained deaths o The goal of forensic anthropology is to extract all information possible regarding the individual themselves and the circumstances of their death Forensic anthropologists can aid law enforcement and the medicolegal community in the following ways: o Age, sex, ancestry and stature, as well as other characteristics of individuation o Cause and manner of death o Postmortem interval – how long the person has been dead o Locating and recovering remains and with the collection of all relevant forensic evidence Forensic Anthropology Protocol Are the remains human? Are the remains of medicolegal significance? o I.e. <50 years have passed since death Do they represent a single individual or the commingled remains of several? When did death occur? How old was the decedent? What was the decedent’s sex? What was the decedent’s race/ancestry? What was the decedent’s stature? Body weight? Physique? Does the skeleton (or body) exhibit any significant anatomical anomalies, signs of old disease and injuries or other characteristics, which singly or in combination, are sufficiently unique to provide positive identification of the decedent? What was the cause of death? o E.g. gunshot wound, blunt force trauma, tuberculosis, unknown What was the manner of death? o I.e. natural, accident, suicide, homicide, unknown Is it a forensic case? Is it bone? o Visual inspection o Microscopic inspection o Chemical analysis Is it human? o Maturity o Architecture o 25-30% of all bones turned into forensic anthropologists are non-human Contemporary vs. Noncontemporary State of preservation Body modification o Cranial deformation o Dental modifications o Dental attrition (wear) o Prosthetics, etc. o Red ochre (present on Native American remains) o Copper and other metal staining o Can be deliberate or unintentional Personal belongings o Clothes o Jewelry o Grave goods Conditions of interment o Body treatment o Body arrangement o Pretreatment o Burial enclosure Age Determination Juvenile o Dental eruption o Dental development o Long bone length o Epiphyseal union Adult o Pubic symphysis morphology o Auricular surface morphology o Basilar suture fusion o Ectocranial suture closure o Medial clavicle fusion o Sternal rib end morphology o Osteoarthritis, attrition, bone density Determination of Sex Cranium o Forehead – vertical in females, angled backwards in males o Supraorbital ridges – males have more raised bone, females are smoother or fainter o Orbital margin – sharper in females, blunt in males o Mastoid process – larger in males, smaller in females o Muscle markings – more pronounced in males than females o Mandible angle – 90 degree angle in males, angled back in females o Chin shape – females are more pointed, males more blunt Pelvis (Innominate, Os coxa: ilium, ischium, pubis) o Sciatic notch – wider in females, narrower in males o Ventral arc o Sub-pubic angle – best thing to look at Rounded U-shape in females, V-shaped in male o Superior inlet – what a baby goes through o Auricular surface o Pre-auricular sulcus o Scars of parturition Post-cranial Measurements o Humerus – maximum head diameter, transverse head diameter, septal aperture o Femur – maximum head diameter; bicondylar width; midshaft circumference Ancestry Affiliation European, Asian or African Visual identification of ancestry in the skeleton o Nose – width and length; lower border of nose o Face – root, bridge and spine; lower eye border o Jaws/teeth – palatal shape, presence/absence of shovel-shaped incisors; angle of jaw, pointed or rounded o Vault – sutures
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