Hair/Fiber and Physcial/Trace Evidence and Bones

Natural Fabrics

• Made of animal or plant based fibers

• Ex. - cotton, silk, wool

Synthetic fabrics

• Man made and produced entirely from chemicals

• Ex. polyester, rayon, acrylic

• Polyester is the single most used textile overtaking cotton

Fiber diameter

• Diameter of a circle is in a straight line segment that passes through the center of the circle and whose endpoints lie on the circle 

• Since hair can be variable this can only provide a general range

  • As a person ages hair becomes thicker and stronger

  • Thicker hair is found closer to the root of the hair 

  • Diameter can range 

Natural Fibers examples

Wool, cotton, hemp and flax, silk, and jute

Wool Fibers

• Natural hair grown on sheep, composed of protein substance called keratin 

• Have crimps of curls which create pockets and give a spongy feel and create insulation 

• Outside surface of the fiber consists of a series of serrated scales which overlap each other which make it possible for the fibers to cling together and produce felt

Cotton Fibers

• Among the most important textile fiber in the world

• A natural vegetable fiber produced in the cotton plant

Hemp and Flax Fibers

• Cellulose fibers with properties that are similar and are scarcely differentiated at the fiber form 

• Differentiation is complicated by treatment processes

Jute Fibers

• One of the most affordable natural fibers

• Harder than other textile fibers

• Environmentally friendly 

• Normally used for sacking burlap and twine as a backing material for tufted carpets

Silk Fibers

• Made of proteins secreted by a caterpillar which feed on select plants and spin cocoons as a protective shell to perpetuate the life 

• Man interferes this life cycle at the cocoon stage to obtain the silk which is a continuous filament of commercial importance

Synthetic Fibers Examples

Rayon, acrylic, polyester, nylon and spun glass

Rayon Fibers

• Will absorb moisture, breathable, comfortable to wear, easily dyed in vivid colors 

• Doesn’t build up static electricity, won’t pill unless the fabric is made from short, low twist yarns 

• Shares many properties similar to cotton

• Comfortable, soft to the skin, has the moderate dry strength and abrasion resistance

Acrylic Fibers

• Can be thought of as artificial wool imitation 

• Has wools warmth and softness but doesn’t absorb water but wicks moisture to the surface where it evaporates

Polyester Fibers

• Most commonly used synthetic fiber

• Often blended with other fibers like cotton 

• Have good elasticity, wrinkle resistance, shape retention, excellent wash and wear performance, and durability 

• Poor in moisture absorption so wearer feels hot and sticky, produces static electricity easily which results in clothing absorbing dust and clinging to the body, poor comfort 

Nylon Fibers

• Doesn’t absorb water but also means that movement combine to create static electricity 

• Has some of the look and feel of silk 

• Used in sheer hosiery, sails, parachutes, blouses, gowns, veils, swimsuits, lingerie, car ties 

• Replaced wool as the fiber most used in carpets

Spun Glass Fibers

• Glass is one of the strongest textile fibers having greater specific tensile strength than steel wire of the same diameter at a lower weight 

• Excellent heat resistance 

• Noncombustible, highly resistant to attack by most chemicals and unaffected by sunlight, fungus or bacteria 

Physical Evidence

• Any item that establishes a link between a crime and a victim of perpetrator

• Ex. - document, hair, fibers, fingerprints, soil, blood

Class Evidence Characteristics

• Physical evidence that can be associated only with a group (not a single source)

• Goal is to reduce the number of suspects but it can’t pinpoint one person or source 

• Ex. - blood type, fibers, paint

Individual Evidence Characteristics

• Physical evidence that can be connected to a common source with a high degree of certainty 

• Ex. anything that contains nuclear DNA, tool marks, fingerprints

Hair as class Evidence

• Hair varies in texture from one region of the body to another

• It can only be used to determine similarities and not a single source connection 

• Ex. - round/oval cross section in caucasians, oval/flat in cross sections in african americans 

Hair analysis

• Can be used to match a suspect with a crime scene

• Can be microscopically analyzed for similarity 

• Comparisons continue to improve as forensic techniques improve

Hair identification

• Hair offers some benefits to forensic scientist because

  • Hair resist decomposition

  • Hari may indicate drug use of poisoning 

Hair Structure

• Cuticle - outer coating composed of overlapping scales

• Cortext - protein rich structure around the medulla that contains pigment

• Medulla - central core (may be absent)

Hair Follicle

• Part of the skin which grows a hair by packing old cells together 

• Attached inside the top of the follicle are sebaceous glands which are tiny sebum producing glands in almost all skin except on the palms, lips, and soles of the feet

Root of Hair

• Hair shaft - part of the hair not anchored to the follicle and much of this is exposed at the skin's surface 

• Hair root - rest of the hair which is anchored in the follicle lies below the surface of the skin

Cuticle

• Outside covering of the hair

• Formed with flat overlapping and hardened scales

• Characteristics may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people 

• Comparing scales, look for 

  • How many there are per centimeter

  • How much they overlap

  • What is their overall shape

  • How much they protrude from the surface

  • What is their thickness

  • Is there pigment present 

Cortex

• Thickest hair layer located in the interior portion of the hair between the cuticle and the medulla

• Contains the hair pigments (melanin) 

  • Pigment is absent in gray hair 

• Distribution of the cortex is considered the most important component when attempting to distinguish between different people 

• Microscopic examination can also reveal the condition and shape of the root and tip

• Cortex varies in thickness, texture, and color

Medulla

• Innermost (center) layer of the hair

• Most noticeable hair feature in many species

• Characteristics may be important in distinguishing between different species by no useful in distinguishing between people

• May vary in thickness, continuity (continuous structure or broken pieces), and opacity (how much light is able to pass through it)

• May be absent 

• Patterns - continuous, interrupted, fragmented, absent 

Index

• Describes the thickness of the medulla layer

• Calculated by measuring the diameter of the medulla and dividing it by the diameter of the hair 

Hair DNA Analysis

• Only possible if “bulb” at the base of the hair is intact

• Hair bulb forms the base of the hair follicle

• In the hair bulb, living cells divide and grow to build the hair shaft

• Blood vessels nourish the cells in the hair bulb and deliver hormones that modify hair growth and structure at different times of life 

Probability of detecting DNA in hair roots is more likely….

for hair being examined in its different growth phases

Anagen hair

•  early growth

Catagen hair

middle growth

Telogen hair

•  final phases 

Mitochondrial DNA

• Found outside of the nucleus 

• Transmitted only from mother to child 

• Can be extracted from the hair shaft

• All positive microscopic hair comparisons must be confirmed by DNA analysis

Hair collection baseline

• Hair comparisons involve either head hair or pubic hair 

• Head hair - 50 full length head hairs from all areas of the scalp will normally ensure a representative sampling 

• Pubic hair - 24 full length 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 autopsy 

Importance of Animal hair

• DNA could be removed from animals mouth (if bitten)

• Blood samples could be removed from animals fur, feet, etc

Animal hair types

• Guard hairs

• Fur or wool hair

• Tactile hairs

Guard hairs

longer, thicker, straight, and from the outer protective coat of the animal

Fur or Wool hair

thin, soft, kinked, and not straight found close to the skin forming an insulating inner coat

Tactile hairs

provide sensory functions and typically found on the head of animals such as whiskers

Types of Cuticle Scale Patterns

• Imbricate

• Spinous

• Coronal

Imbricate

scales are in a random overlapping pattern and are often flattened

Spinous

scales have a spiny appearance that overlap

Coronal

crown like scale pattern in very fine hairs that look like a stack of paper cups

Medulla (animal hair)

• Innermost layer of hair and serves as the marrow of the hair

• Composed of air filled compartments that are typically harder to see in human hair compared to other animals 

• Patterns - absent, fragmented, intermittent, continuous 

Medulla Structures

• Amorphous  

• Uniserial  

• Multiserial

• Cellular

• Lattice

Amorphous

medulla appears as a solid line but lacks a clear pattern or structure 

Uniserial

has one ladder row of components running down the hair longitudinally

Multiserial

has multiple ladder rows of components running down the hair longitudinally 

Cellular

wide band of randomly shaped cell-like structures 

Lattice

can occupy nearly the entire width of the hair with small circle shaped components

Index

• Describes the thickness of the medulla layer

• Humans - usually 0.333 or less

• Animal - 0.50 or greater 

• Calculations - divide the medullar width by the width of the cortex

Hair Diameter

• Human - usually range of 0.05 - 0.15mm

• Animal - can be narrower or coarser

Hair length

Animal hair is normally shorter then human hair

Color Consistency

• Human - generally consists in pigment throughout the length of the hair shaft with slight increase in density toward the cuticle

• Animal - color is more centrally distributed although more dense toward the medulla

Color banding

• Human - when untreated will lack banding 

• Animal - can have a banded appearance 

Medulla Comparison

• Human - have only an amorphous medulla structure

• Animal - can have complex regular/geometric cellular medulla

Medulla Index

• Human - almost always less than ⅓

• Animal - usually greater than ⅓ 

Shaft

• Animals hairs can have different shapes than human such as the spatulate shape found in rodent hairs

Root

• Human - has a bulb or ribbon shaped root

• Animal - have different root shapes, typically brush like

Tip

• Human - usually cut or frayed at the tip

• Animal - generally naturally tapered

Scales

• Human - exhibits irregular annular scale patterns 

• Animal - has a variety of types and can have more than one type in the same hair 

Animal Hair comparisons

• Don’t possess enough individual microscopic characteristics to exclude other similar animals and be associated with a unique individual 

• If questioned hair exhibits the same microscopic characteristics as the known hairs it is concluded that the hair is consistent with originating from that animal 

• Think about diameter, medulla, scales, general patterns

Superior

 toward the head

Inferior

toward the feet

Dorsal

 toward the back

Ventral

 toward the front

Proximal

 toward the point of attachment

Distal

 away from the point of attachment

Supine

lying on the back side

Prone

 lying on the belly side

Anterior

front side 

Posterior

back side

Medial

 closer to the middle of the body

Lateral

away from the middle of the body

Bone basics

• Bone comprises the vertebrate skeleton in animals which protects various organs of the body 

• Produces red and white blood cells, store minerals, prodive structure and support for the body, and enable mobility 

• Come in variety of shapes and sizes and have a complex internal and external structure that is lightweight and strong 

Long bones

• femur (thigh), tibia (larger shin), fibula (smaller shin), humerus (upper arm), radius (larger forearm), ulna (smaller forearm)

Short bones

 carpals of the wrist, tarsals of the ankle

Flat bones

 skull, sternum (breast bone), capula (shoulder bone)

Irregular bones

vertebrae (spine), pelvis

Skull

• Bony structure that forms the head in vertebrates

• Supports the structure of the face and provides a protective cavity for the brain

Mandible

• Lower jaw or jawbone

• Largest, strongest bone in the human face

• Holds the lower teeth in place

Vertebra

• Individual bones that comprise the vertebral column that has curves

• Natural curves have more strength than a straight line so can support the weight of the body and provide balance needed to walk

• Sections of vertebral column - cervical, thoracic, lumbar 

Rib cage

• Protects heart and lungs in the thoracic cavity

• Aid in respiration 

• Provide support for the upper limbs

• Three main classifications based on different points of attachment 

  • True/fixed ribs

    • 1 through 7 

    • Attached in front to the sternum by a costal cartilage

  • False ribs

    • 8 through 10

    • Not attached to the sternum but to the costal cartilage of the 7th rib above 

  • Floating ribs 

    • 11 and 12

    • Only attached to the vertebrae

Pelvis

• Area of attachment for the upper leg bones

• Contains portions of the vertebrate column 

Femur

• Aka the thigh bone

• Longest bone and considered to be the strongest bone in the body

Patella

• Known as the kneecap

• Flat circular triangular bone

• Protects the knee joint

Fibula

• Long, thin lateral bone of the lower leg

• Parallel to the tibia

• Helps stabilize the ankle and supporting the muscles of the lower leg

Tibia

• Aka the shinbone

• Second largest bone in the body

Measuring Bones to estimate height

• By measuring a single bone the estimated height of the individual can be calculated

• Important to properly identify the bone to know what formula to use 

• Select a long bone to measure - humerus, radius, ulna, femur, tibia, fibula 

• Knowing the race and sex of the individual the bone is from will help increase the accuracy of the calculation 

• Measure yourself

  • Select a long bone

  • Measure bone length in cm

  • Use reference table for formula

  • Once you calculate height compare to your actual height (remember this is an estimate)

Skull and Mandible Sex determination

• Male

  • Cranial mass is more blocky and massive

  • Supraorbital margin is rather round and dull

  • Zygomatic bone is more pronounced 

  • Mandible is more squared 

  • Deeper cranial mass

  • Superciliary arch is large and more pronounced 

• Female

  • Cranial mass is more rounder and tapers at the top 

  • Supraorbital margin is sharper 

  • Mandible is more rounded 

Pelvis sex determination

• Male 

  • Bone is heavier, thicker

  • Pelvic cavity is narrow and deep

  • Pelvic inlet is heart shaped and smaller

  • Pubic arch angle is acuter

  • Coccyx (tail bone) is less flexible, more curved

  • Sacrum is long and narrow

• Female

  • Bone is lighter, thinner

  • Pelvic cavity is wide and shallow

  • Pelvic inlet is round and oval

  • Pubic arch angle is large

  • Coccyx (tail bone) is more flexible, straighter

  • Sacrum is shorter, wider, curved more posteriorly 

Humerus sex determination

• Transverse diameter of the head

  • Male - greater than 47mm

  • Female - less than 43mm

• Vertical diameter of the head 

  • Male - about 48.8mm

  • Female - about 42.7mm

• Width between epicondyles

  • Male - about 63.9mm

  • Female - about 56.8mm

• Total length of the humerus 

  • Male - about 339mm

  • Female - about 305.9mm

Femur sex determination

• Strongest and longest bone in the human skeleton

• Male femurs are stronger and longer than female

• Diameter of the head of male femurs is greater than female

• Vertical diameter of the head

  • Male - greater than 46.5mm

  • Female - less than 43.5mm

• Bicondylar width 

  • Male - greater than 76mm

  • Female - less than 74mm

• Trochanter length of the femur

  • Male - greater than 430mm

  • Female - less than 405mm

Matrix

• Non living hardened material surrounding the bone cells 

• Composed of manly Ca and P compounds along with proteins that make bone hard and slightly flexible while still maintaining a very strong structure

Canaliculi

microscopic canals between the lacunae of ossified bones

Approximating of age

• Counting the number of osteons resent in a bone sample and taking measurements of the Haversian Canal diameters 

• Use this information to calculate the estimated age of a bone sample at that time

Osteons

• Thin and long cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi which transport blood

• These are solid portions of bone that run its length 

• Easily viewed with a microscope

Counting on onsteons

• View a bone specimen so it completely fills a medium power field of view

• Count the total number of osteons present in the entire medium power filed of view 

• For small bone samples

  • Use high power

  • Determine number of osteons present by counting the Haversian Canals present 

  • Randomly more the sample to 10 new locations and repeat the process

  • Then calculate the average number of osteons viewed under high power to the hundredths place

  • Multiple this average by 16 to generate the total number of osteons counted under medium power

Haversion canal

• Hollow tube in the center of each osteon 

• Contain small blood vessels