Chapter 11 Hairs and Fibers

Hair Evidence

Common trace evidence type in criminal investigations.

Shed Hairs

Hairs easily lost from individuals during growth.

Forensic Hair Analysis

Examines hair to establish associations in crimes.

Association Demonstration

Shows links between suspects and crime scenes.

Exculpatory Evidence

Evidence that can prove a suspect's innocence.

Microscopic Hair Examination

Analyzes hair but cannot definitively identify individuals.

Morphological Characteristics

Physical traits used to analyze and compare hairs.

Human vs Animal Hair

Distinguishes hair origin based on characteristics.

Known Sample Comparison

Compares unknown hair to a known sample.

Identification Phase

Initial analysis to categorize hair types.

Telogen Root

Hair root phase indicating shedding or rest.

Microscopic Comparison

Evaluates hair samples for shared characteristics.

Pattern-Recognition Process

Instantly identifies similarities in hair characteristics.

Step-by-Step Analysis

Detailed examination of hair comparison points.

Points for Comparison

Specific features analyzed in hair samples.

Association Criteria

Microscopic traits must match in questioned hair.

Subjective Interpretation

Examiner's judgment on the significance of traits.

Animal Hair Identification

Used by biologists and researchers for analysis.

Significance of Animal Hair

Less than human hair but still useful.

Dog Hair Evidence

Can link a suspect to a victim's item.

Caucasian Characteristics

Specific traits found in human hair samples.

Growth Phases of Hair

Includes anagen, catagen, and telogen stages.

Forensic Investigation Utility

Animal hair can provide valuable forensic insights.

Cuticle

Outermost hair layer protecting from damage.

Cortex

Main body of hair containing pigment granules.

Medulla

Central core of hair, varies in thickness.

Imbricate pattern

Irregular scale pattern in human hair cuticle.

Cortical fusi

Small air spaces in the cortex of hair.

Eumelanin

Pigment granule for brown and black hair.

Phaeomelanin

Pigment granule for yellow and red hair.

Ovoid bodies

Dense, oval-shaped pigment clumps in hair.

Hair root morphology

Shape of hair root indicating species origin.

Telogen phase

Resting phase when hair naturally falls out.

Animal hair medulla

Thicker than 2/3 of hair shaft diameter.

Human hair medulla

Less than 2/3 of hair shaft diameter.

Environmental influences

Factors affecting hair characteristics and growth.

Growth stage

Phase of hair development at separation.

Hair identification

Process of determining hair origin and type.

Hair pigmentation

Color derived from pigment granules in cortex.

Cuticle thickness

Measurement of cuticle layer's width.

Cuticular margin

Outer edge of cuticle, can be smooth or ragged.

Hair damage

Alterations in hair structure due to external factors.

Scales

Flattened cells in cuticle overlapping like shingles.

Species identification

Determining hair origin based on morphological features.

Microscopic comparison

Analyzing hair under microscope for identification.

Environmental insults

External factors causing damage to hair structure.

Dermal Papillae

Base of hair follicle where growth occurs.

Anagen Phase

Active growth phase; 80-95% of hairs.

Catagen Phase

Transitional growth phase; bulbous root develops.

Telogen Phase

Dormant phase; 10-20% of hairs present.

Bulbous Root

Characteristic of human hair roots.

Speared Root

Characteristic of animal hair roots.

Forcibly Removed Hair

May have tissue attached for DNA analysis.

Hair Color

Determined by pigment granules and light properties.

Hair Characteristics

Includes hue, value, and intensity of color.

Distal End

Tip of hair; varies in morphology.

Abraded Hair Tip

Tip altered by grooming or abrasion.

Cut Hair Tip

Tip resulting from cutting hair.

Worn Razor-Cut Tip

Tip from hair cut with a razor.

Decomposed Hair

Hairs from decomposed bodies show specific traits.

Hair Growth Rate

Hairs shed naturally as new growth occurs.

Microscopic Characteristics

Unique features observed under a microscope.

Nuclear DNA Analysis

Used on hair with follicular material attached.

Variation in Hair Color

Less variation within individuals than among them.

Environmental Exposure

Can cause color variation in individual hairs.

Hair Follicle

Structure from which hair grows.

Hair Morphology

Study of hair structure and characteristics.

Hair Comparison Process

Analyzing hair for forensic identification.

Forensic Hair Examination

Analyzing hair for legal investigations.

Hair Sample Growth

Hair may grow over significant time gaps.

Hair Diameter

Ranges from 40-120 micrometers in size.

Racial Classification

Diameter aids in determining racial group.

Hair Collection Importance

Hairs must persist to be meaningful evidence.

Evidence Recovery Locations

Occurs at crime scene and crime lab.

Evidence Packaging

Proper packaging prevents contamination and loss.

Forensic Discipline Order

Trace analysis must precede other forensic tests.

Stereomicroscope Examination

Initial examination done under low magnification.

Glass Slide Mounting

Hairs are mounted for high power examination.

Representative Sample

Includes distinct types of hairs observed.

Targeted Search Method

Focuses on known samples alongside evidentiary items.

Microscopic Analysis

Uses 50x to 400x magnification for details.

Body Area Classification

Determines origin based on hair characteristics.

Head Hairs

Typically longest, uniform diameter, often cut.

Pubic Hairs

Distinctive characteristics differentiate them from head hairs.

Facial Hairs

Includes beard and mustache hair types. Coarse hairs with triangular cross section and razor-cut tips.

Limb Hairs

Hairs from arms and legs categorized separately. Shorter, arc-like, often abraded or tapered at tips.

Chest Hairs

Hair from the chest area, unique morphology.

Axillary Hairs

Hair from armpits, identifiable by specific traits.

Eyebrow/Eyelash Hairs

Short, fine hairs from facial regions.

Environmental Alterations

Conditions like sunlight affect hair appearance.

Chemical Alterations

Dyes and treatments change natural hair characteristics.

Head Hair Samples

Not suitable for comparison years after crime.

Pubic Hair

Coarse, wiry, with diameter variation and medulla.

Pubic Hair Stability

Less change over time, suitable for comparison later.

Known Pubic Hair Sample

At least 25 full-length hairs recommended post-crime.

Nuclear DNA Typing

Requires nucleated cells, effective for hair analysis.

Microscopic Hair Analysis

Distinguishes hair types and provides contextual information.

mtDNA

Maternally inherited, not unique to individuals.

Microscopic Examination Importance

Essential before DNA analysis due to destruction risk.

Hair Examination Techniques

Includes microscopic and DNA analysis for evidence.