Fiber & Hair Analysis Hair Evidence • Hair is composed primarily of the protein keratin • Defined as slender outgrowths of the skin of mammals • Each species of animal possesses hair with characteristic length, color, shape, root appearance, and internal microscopic features that distinguish one animal from another • Variability exists in types of hairs found on body of an animal • Humans – Head, pubic region, arms, legs & other body areas have characteristics that can determine their origin • Hair types include coarse outer hairs or guard hairs (finer fur hairs, tactile hairs [whiskers], & others that originate from tail & mane) • Value of hair as evidence depends on: – Types of hair recovered – Condition of hair – # of hairs found • Comparison of microscopic characteristics of questioned hairs to known hair samples helps determine whether a transfer may have occurred Hair Morphology • Hair is an appendage of the skin that grows out of an organ known as the hair folicle • Grows from hair follicle • Root is embedded in follicle • Shaft has 3 parts – Cuticle – Cortex – medulla • Terminates at a tip end Anatomy of a Hair bsapp.com bsapp.com Follicle • Hair is an appendage of the skin that grows out of a hair follicle. bsapp.com The follicle contains more than enough cells for simple DNA Analysis bsapp.com Root • The length of a hair extends from the root embedded in the follicle. • A single root contains sufficient DNA for analysis bsapp.com Root • The root and other surrounding cells in the hair follicle provide the tools necessary to produce hair and continue its growth. • When pulled from the head, some translucent tissue surrounding the hair’s shaft near the root may be found. This is called a follicular tag. • By using DNA analysis on the follicular tag, the hair may be individualized. 11 Cuticle • Is the outside covering of hair • Gives hair resistance to chemical composition & stability (retaining features over a long period of time • Formed by overlapping scales that always point toward the tip end • Scale pattern is useful in species identification but not a useful characteristic for individualizing human hair • Variety of patterns formed by animal hair makes it an important feature for species identification a) Human b) Dog c) Deer d) Rabbit e) cat f) Horse Cortex • Main body of hair shaft • The interior of the hair • It is embedded with pigment granules that give hair its color • Color, shape, distribution of the granules provide important points of comparison Pigment granules are absent in grey hairs bsapp.com Medulla • Group of cells having appearance of a central canal running through a hair • Sometimes it is the predominant feature, occupying more than ½ the diameter (varies by species) • Medullary index is the diameter of medulla relative to diameter of hair shaft – Humans is less than 1/3 – Other animals, value is ½ or greater • Presence & appearance vary between individuals & among the hairs in a given individual • Medulla patterns – Continuous – Interrupted – Fragmented – Absent all together • Human head hairs the medulla is usually absent or fragmented; rarely have continuous •Animal medulla is either continuous or interrupted • Shape of medulla – Cylindrical: humans & many animals – Patterned shape: other animals • Ex. Medulla of cat resembles a string of pearls • Ex. Deer medulla is spherical cells occupying the entire hair shaft CAT DEER HUMAN DOG RABBIT CAT DEER Hair Growth • Regions of the body that are primarily used in forensic comparisons are the head & pubic areas • As hairs undergo cyclical growth ( anagen) & resting phase (telogen), the visible microscopic characteristics are sufficient to determine the phase of growth of the hair • Anagen phase – Hair actively growing – Materials are deposited in hair shaft by cells found in follicle – Metabolically active & dividing cells above & around the dermal papilla of the follicle grow upward during this phase to form – medulla, cortex, cuticle, & root sheath – 80-90% of hairs • Telogen phase – Follicle is dormant or resting – 10-18% • Catagen phase – Transition period between anagen & telogen – 2% • Hairs routinely lost during telogen phase & become a primary source of evidentiary material • Hairs can also become dislodged from the body while they are in an actively growing state (anagen) • Microscope appearance of root area will allow for the determination of growth phase • When pulled from the root, some anagen hairs will have a follicular tag – Is a translucent piece of tissue surrounding the hair’s shaft near the root – Contains the richest source of DNA associated w/hair Naturally shed hair - Displays undamaged, club shaped roots Forcibly removed hair Forcibly removed hair w/tissue attached - Will exhibit stretching & damage to root area Comparing Strands • The comparison microscope is an indispensable tool for comparing the morphological characteristics of hair. • When comparing strands of human hair, the criminalist is particularly interested in matching the color, length, and diameter. • A careful microscopic examination of hair will reveal morphological features that can distinguish human hair from the hair of animals. • Scale structure, medullary index, and medullary shape are particularly important in animal hair identification. 28 Comparing Strands • Other important features for comparing human hair are: – the presence or absence of a medulla – the distribution, shape, and color intensity of the pigment granules present in the cortex • The most common request is to determine whether or not hair recovered at the crime scene compares to hair removed from the suspect. • However, microscopic hair examinations tend to be subjective and highly dependant on the skills and integrity of the analyst. 29 Questions • Can the body area from which a hair originated be determined? • Can the racial origin of hair be determined? • Can the age and sex of an individual be determined from a hair sample? • Is it possible to determine if a hair was forcibly removed from the body? • Are efforts being made to individualize human hair? • Can DNA individualize a human hair? 30 Hair Microscopy • Done w/light microscopy • Is a 2 step process – ID of questioned hairs – Comparison of questioned & known hairs • Purpose – To ascertain whether 2 or more individuals could have come into contact w/an object – Particularly useful in crimes of violence (homicide, sexual assault, & aggravated assault) where physical contact may have occurred • Value of hair evidence – Related to the variability of hair characteristics between individuals in the population – Factors that impact the reliability of a hair assoication • • • • Experience Training Suitability of known hair standards Adequacy of equipment Hair and DNA • Recent major breakthroughs in DNA profiling have extended this technology to the individualization of human hair. • The probability of detecting DNA in hair roots is more likely for hair being examined in its anagen or early growth phase as opposed to its catagen (middle) or telogen (final) phases. • Often, when hair is forcibly removed a follicular tag, a translucent piece of tissue surrounding the hair’s shaft near the root may be present. • This has proven to be a rich source of nuclear DNA associated with hair. 33 Hair and Mitochondrial DNA • Mitochondrial DNA can be extracted from the hair shaft. • Mitochondrial DNA is found in cellular material located outside of the nucleus and it is transmitted only from the mother to child. • As a rule, all positive microscopical hair comparisons must be confirmed by DNA analysis. 34 Collection and Preservation • As a general rule, forensic hair comparisons involve either head hair or pubic hair. • The collection of 50 full-length hairs from all areas of the scalp will normally ensure a representative sampling of head hair. • A minimum collection of two dozen fulllength pubic hairs should cover the range of characteristics present in pubic hair. • Hair samples are also collected from the victims of suspicious deaths during an 35 Steps in Hair Examination Process • Determine if hair in question is from animal or human • If from animal – Identify the type of animal (species, not specific animal) Animal Hairs • Hairs can vary greatly in color & length on different areas of the body; therefore, you should collect reference samples from each area • Samples should contain: – Full length hairs – Combings & pluckings – If animal isn’t available for collection, a brush or comb used on that animal may be substituted • Animal hairs found at scene or on clothing may have come from a fur coat or pelt – Since these are usually artificially dyed & don’t have a root, it’s preferred that entire garment be obtained for suitable samples Human Hairs • An individual sheds approximately 100 head hairs each day • Body area determination – Characteristics used • Length, shape, size, color, stiffness, curliness, microscopic appearance, pigmentation, medullar appearance – Hairs that exhibit microscopic characteristics shared by different anatomical areas are called body hairs • Include hair on upper legs, lower abdomen, and back - Head & pubic hairs are used most for forensic work because there is a wide range of interpersonal variation in these types of hair Head hairs • Longest hairs on human body • Have uniform diameter and, often, a cut tip • Are subject to more alteration than hairs from other body areas Razor-cut hair Hair w/cut tip Split hair • Alterations to natural appearance include – Dyes, rinses, permanents, frosts • Environmental alterations – Excessive sunlight, wind, dryness • Because of potential for alteration, it is recommended that head hair samples be obtained as soon as possible from suspects & victims of crime • Samples obtained years after a crime are generally not suitable for meaningful comparison purposes • Known samples – Need a random sampling of hair from different areas of scalp – # of hairs required vary – General rule is to obtain at least 25 fulllength hairs, which includes both plucked & combed, packaged separately Pubic Hairs • Not subject to as much change as head hairs over time • Therefore, a sample taken a year or more after a crime may still be suitable for a meaningful comparison • It’s recommended that known samples be collected ASAP • Samples should contain at least 25 full-length hairs taken from different areas of the pubic region • Characteristics – Course & wiry in appearance – Considerable diameter variation or buckling (twisting of hair shaft) – Often have a continuous to discontinuous medulla – Tapered tips are common, but these hairs may also be abraded or cut Hair showing buckling Facial Hairs • More commonly called beard or mustache hairs • Characteristics – Coarse in appearance – Have a triangular cross section – Heavy shouldering or troughs are observed under magnification – Wide medulla – Razor cut tip • Significance of association of facial hairs may not be as great as head & pubic hair associations Limb Hairs • Hairs from legs & arms • Characteristics – Shorter in length, arc-like shape, often abraded or tapered at tips, pigment is generally granular in appearance, medulla is trace to discontinuous • Not routinely compared in forensic lab • There are differences b/t individuals, but they’re not considered sufficient to allow limb hairs to be of value for meaningful comparison Fringe Hairs • Hair originating from areas of the body outside those specifically designated as head or pubic • Not suitable for significant comparison purposes • Examples – Neck, sideburns, abdomen, upper leg & back Other body area hairs • Not routinely compared • Presence may help corroborate information obtained during an investigation (just like limb & fringe hairs) • Examples – Axillary (underarm), chest, eye, nose Racial Determination • Head hairs are best for determining race • Head hair from infants can be difficult to analyze • Also, hairs from individuals of mixed racial ancestry may possess microscopic characteristic attributed to more than one racial group • Caucasoid (European) – Fine to medium courseness – Generally straight or wavy in appearance – Colors range from blonde to brown to black – Hair shafts vary from round to oval in cross section – Have fine to medium sized, evenly distributed pigment granules • Mongoloid (Asian) – – – – – – – – Regularly coarse straight circular in x-section Wider diameter than other racial groups Cuticle is usually significantly thicker than that of Negroid or Caucasian hairs Medulla is continuous & wide Cortex contains pigment granules that are generally larger in size compared to Caucasian hairs Have characteristic red appearance • Negroid (African) – Regularly curly or kinky – Flattened x-section – Can appear as curly, wavy or coiled – Pigment granules are larger than those in Mongoloid & Caucasian – Pigments are grouped in clumps of different shapes & sizes – Density of pigment in cortex may be so great as to make hair opaque – Shaft has variation or apparent variation in diameter – Buckling can be present – Hair shaft frequently splits along the lenght Age & Sex • Age of individual cannot be determined definitively by microscopic examination of hair • However, appearance of certain hairs, such as those of infants & elderly individuals, may provide a general age • How? – Infant hair is generally finer & less distinctive in appearance – As one ages, hair can undergo pigment loss & changes in configuration of hair shaft to become much finer & more vaiable in diameter • Sex of individual is difficult to determine – However, longer treated hairs are more frequently encountered in females • If hair is forcibly remove, sex can be determined using follicular tag Treatment & Removal • Presence of dyes or rinses can be identified through microscopic examination of hair • Head hairs grow at the rate of 1cm/month – Approximate time of treatment can be determined by measuring the length of untreated area – Direct, side-by-side comparison of color of question & known artifically treated hairs is typically conducted by hair examiner Biological or Environmental Alterations • When hairs originated from a body in a state of decomposition, a dark band may appear near the root of the hair – Called postmortem root band Conclusions • Several possible conclusions which can be reached from examination & comparison of human hair – Questioned hair exhibits same microscopic characteristics as know hair & is consistent w/originating from source of known hairs – Questioned hair is microscopically dissimilar to hairs found in known sample & cannot be associated to the source of known hairs – Similarities & slight differences were observed b/t questioned hair & known hair sample. No conclusion could be reached as to whether the questioned hair originated from same source as known hairs • When a hair exhibits same microscopic characteristics as hairs in known sample, a qualifying statement may be added – Hair comparisons are not a basis for absolute personal identification. It sould be noted, however, that because it is unusual to find hairs from 2 different individuals that exhibit the same microscopic characteristics, a microscopic association or match is the basis for a strong association Significance of Hair Evidence • • • • • Depends on method of collection Processing techniques used Methodology of hair examination Experience of hair examiner Head & pubic hairs are generally viewed as more significant than hairs from other body areas • Certain case situations affect significance of identifying hairs – When a family member possibly involved in crime • Location, #, condition (forcibly pulled or burnt) – Involvement of victim’s associates • Dates, coworkers, other people who may have logical contact w/or access to victim &/or crime scene – Situations involving strangers have greatest significance Hair affected by burning Textile fibers • Can place a suspect at the crime scene • Fibers can be exchanged between 2 individuals, between an individual & an object, & between 2 objects Importance of fiber matched to a crime scene • When fibers are matched w/specific source, a value is placed on that association • Value is dependent on: – – – – type of fiber Location of fibers at crime scene or on victim # of different fibers at crime scene # of different fibers on the victim that match clothing of suspect Fiber Evidence • Fiber – smallest unit of textile – Length much greater than diameter – Can be naturally occurring or synthetic – Can be spun w/other fibers to form a yarn that can be woven or knitted to form a fabric Fiber Evidence • The quality of the fiber evidence depends on the ability of the criminalist to identify the origin of the fiber or at least be able to narrow the possibilities to a limited number of sources. • Obviously, if the examiner is presented with fabrics that can be exactly fitted together at their torn edges, it is a virtual certainty that the fabrics were of common origin. 69 Fiber Evidence • Microscopic comparisons between questioned and standard/reference fibers are initially undertaken for color and diameter characteristics, using a comparison microscope. • Other morphological features that could be important in comparing fibers are: – Lengthwise striations on the surface of the fiber – The presence of delustering particles that reduce shine – The cross-sectional shape of the fiber • Compositional differences may exist in the dyes that were applied to the fibers during the manufacturing 70 process. Transfer of Fiber • Factors affecting transfer of fiber – – – – Type of fiber Length Type of spinning method Type of fabric construction • Can be transferred from – – – – Clothing Carpets Bed Furniture • Can be transferred directly (primary) or indirectly (secondary) • primary occurs when a fiber is transferred from a fabric directly onto a victim’s clothing • Secondary occurs when already transferred fibers on clothing of suspect transfer to clothing of a victim Contact doesn’t always transfer fibers • Certain fabrics do not shed well (donor garment) • Some fabrics don’t retain fibers well (recipient garments) • Factors affecting retention – Construction & composition of fabric – Duration & force of contact – Condition of garment w/regard to damage Methods For Fiber Comparison • The visible light microspectrophotometer is a convenient way for analysts to compare the colors of fibers through spectral patterns. • A more detailed analysis of the fiber’s dye composition can be obtained through a chromatographic separation. • Infrared spectrophotometry is a rapid and reliable method for identifying the generic class of fibers, as does the polarizing microscope. • Depending on the class of fiber, each polarized plane of light will have a characteristic index of refraction. 74 Collection and Preservation • The investigator’s task of looking for minute strands of fibers often becomes one of identifying and preserving potential “carriers” of fiber evidence. • Relevant articles of clothing should be packaged carefully in separate paper bags. • If it is necessary to remove a fiber from an object, the investigator must use clean forceps, place it in a small sheet of paper, fold and label the paper, and place the paper packet inside another container. 75 Types of Fibers • Natural fibers are derived in whole from animal or plant sources. – Examples: wool, mohair, cashmere, furs, and cotton. • Man-made fibers are manufactured. – Regenerated fibers are manufactured from natural raw materials and include rayon, acetate, and triacetate. – Synthetic fibers are produced solely from synthetic chemicals and include nylons, polyesters, and acrylics. • Polymers, or macromolecules, are synthetic fibers composed of a large number of atoms arranged in repeating units known as monomers. 76 Natural Fibers • Originate from plants or animals • Common plant fibers – Cotton, flax (linen), ramie, rayon, sisal, jute, hemp, kapok (silky-cotton like substance), & coir (coconut fibers) • Common animal Fibers – Wool (usually from sheep), camel, alpaca, cashmere, mohair – End use of sheep’s wool dictates fineness or coarseness of fibers • Finer fibers used in clothing • Coarser fibers found in carpet – Fiber diameter & degree of scale protrusion are important characteristics Cotton fibers Wool fibers Flax fibers Ramie fibers Kapok fibers Hemp fibers Cotton- Hemp Blend Synthetic Fibers • More than ½ of all fibers used in production of textile materials are synthetic – Polyester, nylon, acrylics,acetates • Some originate from natural materials such as cotton or wood • Amount of production of particular synthetic fiber & its use influence the degree of rarity of a given fiber • Shape of synthetic fiber can determine the value placed on the fiber Cross section of synthetic fibers Cross section of different nylon fibers Fiber Color • Influences value given to a particular fiber identification • Often several dyes are used to give a fiber a desired color • Individual fibers can be colored prior to being spun into yarn • Yarns can be dyed , & fabrics made from them can be dyed • Color can be applied to surface of fabric – as in printed fabrics • How color is applied & absorbed along length of fiber are important comparison charateristics • Color-fading & discoloration can also lend increased value to a fiber association Fiber Number & Location • # of fibers on clothing of a victim identified as matching clothing of suspect is important in determining actual contact – Greater the # of fibers, the more likely that contact actually occurred • Location of fibers on different areas of body or on specific items at scene influences the significance of the fiber association Fabric Type • How fabric is constructed affects the # & types of fibers that may be transferred during contact – Tightly woven or knitted fabrics shed less than loosely knit or woven fabrics – Fabrics composed of filament yarns shed less than fabrics composed of spun yarns. • Age of fabric affects degree of transfer – Newer fabrics may shed more readily because of an abundance of loosely adhering fibers on surface – Worn fabrics may have damaged areas that easily shed fibers – Damage to fabric caused during physical contact greatly increases the likelihood of fiber transfer Fabric Source Determination • It is not possible to say positively that a fiber originated from a particular fabric • inability to positively associate a fiber w/a source in no way diminishes the significance of a fiber association • It’s very helpful to know frequency of occurrence f a particular fabric & fiber, or how many fabrics w/a particular fiber type & color exist, as well as who owns them • If manufacture is known, possibility exists that # of fabric units produced could also be obtained • Once a particular fiber of a certain type, shape, & color is produced & becomes part of a fabric, it occupies an extremely small portion of the fiber/fabric composition • Exception – white cotton & blue cotton fibers (blue jeans) Fiber Transfer & Persistence • Depends on type of fabric, & nature & duration of contact • Transferred fibers are usually lost rather quickly – depends on type of fabric & movement after contact • Clothing of homicide victim would tend to retain transferred fiber for a longer period because victim is not moving • EMS, medical examiners & investigators must handle victim’s clothing carefully to minimize fiber loss • Fibers will be lost is if victim/suspect moves about, brush the clothing or wash it • Nature of contact – Can determine the # of fibers transferred & value placed on their discovery – Violent physical contact of an extended duration will very often result in numerous fiber transfers • Multiple fiber associations – Multiple fiber types found on different items of clothing or fabric from suspect, victim, or scene greatly increase the likelihood that contact occurred between those individuals & the scene – Each associated fiber is considered to be an independent event – Multiple associations undermine a coincidence defense Fiber Evidence: Assigning Significance • Matching dyed synthetic fibers or dyed natural fibers can be very meaningful • Whereas, matching of common fibers, such as white cotton or blue denim cotton would be less significant • Discovery of cross transfers & multiple fiber transfers between suspect’s clothing & victim’s clothing dramatically increasesthe likelihood that these 2 individuals had physical contact • When a fiber examiner matches a questions fiber to a know item of clothing, there are only two possible explanations – Fiber actually originated from the item of clothing – Fiber did not originate from the item of clothing • In order to say that the fiber originated from the item of clothing – the clothing either had to be the only fabric of its type ever produced or still remaining on earth – Or the transfer of biers was directly observed • therefore, fibers examiners will conclude that the fibers could have originated from the clothing or that the fibers are consistent with originating from the clothing • Only way to say that a fiber did not originate from a particular item of clothing is to know the actual history of the garment or to have actually observed the fiber transfer from another garment Paint • Paint spread onto a surface will dry into a hard film that can best be described as consisting of pigments and additives suspended in the binder. • One of the most common types of paint examined in the crime laboratory involves finishes emanating from automobiles. • Automobile manufacturers normally apply a variety of coatings to the body of an automobile. • These coatings may include electrocoat primer, primer surfacer, basecoat, and 103 Methods For Paint Comparison • The wide diversity of automotive paint contributes to the forensic significance of an automobile paint comparison. • Questioned and known specimens are best compared side by side under a stereoscopic microscope for color, surface texture, and color layer sequence. • Pyrolysis gas chromatography and infrared spectrophotometry are invaluable techniques for distinguishing most paint binder formulations, adding further significance to a forensic paint comparison. • Crime laboratories are often asked to identify the make and model of a car from a small amount of paint and will make use of color charts for automobile finishes. 104 Collection and Preservation • Paint chips are most likely found on or near persons or objects involved in hit-and-run incidents. • Paper druggist folds and glass or plastic vials make excellent containers for paint. • Paint smeared or embedded in garments or objects require the whole item to be packaged and sent to the laboratory. • Uncontaminated standard/reference paint must always be collected. • Tools used to gain entry into buildings or safes often contain traces of paint, requiring the tool be collected, along with reference paint samples. 105