Hair Anatomy & Life Cycles
The continuous structural protein that makes up the majority of the hair shaft.
What is keratin?
The polymer composed of repeating glucose units that forms the structural basis of natural plant fibers.
What is cellulose?
The optical instrument used in forensic laboratories to view questioned and known fiber samples side-by-side.
What is a comparison microscope?
The movement of trace hair or fibers from a source immediately onto a victim or suspect during contact.
What is direct (or primary) transfer?
The Georgia metropolitan area where community activism and a series of task force investigations led to the arrest and trial of Wayne Williams.
What is Atlanta?
The three structural layers of the hair shaft, starting from the innermost core to the transparent outer layer.
What are the medulla, cortex, and cuticle?
The primary raw material source from which synthetic polymer fibers are synthesized.
What is petroleum?
The term for the stationary lengthwise threads in a loom, and the term for the crosswise threads woven back and forth through them.
What are warp (lengthwise) and weft (crosswise)?
The mechanism when a pet hair picked up on a suspect's jacket is subsequently deposited onto a victim's car seat.
What is secondary transfer?
The specific source inside Williams's 1970 Chevrolet station wagon that deposited small rayon fibers onto the victim's clothing.
What is the car carpet (or throw rug)?
The pigment-rich layer of the hair shaft that provides the most important points of microscopic comparison between individuals.
What is the cortex?
Two physical advantages synthetic fibers have over natural fibers, and one vulnerability they exhibit under high heat or sun.
What are greater strength and microbial resistance (advantages), and melting or sun degradation (vulnerability)?
The total magnification achieved when combining a 10× ocular lens with a 40× high-power objective lens.
What is 400×?
he primary scientific reason why forensic technicians must collect trace fiber evidence within 24 hours of a crime.
What is an estimated 95% of transferred fibers fall off or are lost after 24 hours?
The distinct physical alteration observed on fibers recovered from victims found in the Chattahoochee River compared to those found on land.
What is color bleaching or loss of intensity?
The three stages of hair development in order from active growth, through follicle regression, to final dormancy.
What are Anagen, Catagen, and Telogen?
The broad evidentiary classification assigned to fiber evidence due to its mass manufacture and non-unique nature.
What is class evidence?
The weave pattern recognized by its diagonal rib appearance, commonly found in heavy workwear and denim.
What is a twill weave?
Three standard physical tools or methods used by field investigators to recover trace fibers from a scene.
What are forceps/tweezers, sticky tape, and special trace vacuums?
The estimated statistical percentage of Atlanta households that actually owned the same carpet found in Williams's bedroom.
What is less than 1 percent (0.013% or 1 in 7,792)?
The translucent tissue surrounding a forcibly pulled root that contains nuclear DNA required for individualization.
What is a follicular tag?
One specific fiber example for each of the three natural fiber origins: animal, plant, and mineral.
What are wool (animal), cotton (plant), and asbestos (mineral)?
The special weave pattern where pairs of warp threads twist around each other to lock horizontal weft threads in place, creating a stable, breathable mesh.
What is a Leno weave?
The foundational forensic concept stating that every physical contact leaves a trace, governing all hair and fiber evidence.
What is Locard's Exchange Principle?
The mathematical principle of probability used by examiners to show that finding multiple distinct fiber types together on a victim becomes exponentially rare.
What is the product rule?