Forensics

Trace Evidence

Trace evidence is small, transferable material left behind at a crime scene; a trace amount is minuscule.

Hair: Class vs. Individual

Hair is considered class evidence unless nuclear DNA is present, which makes it individual evidence.

Anatomy of Hair

The two main parts of the hair are the shaft and the root.

Nuclear DNA Location

In hair, nuclear DNA is found specifically in the hair root.

Root Shape Comparison

Forced-out hair has a stretched, irregular root, whereas naturally shed hair has a rounded, club-shaped root.

Stages of Hair Growth

The three stages of hair growth are anagen, catagen, and telogen.

Hair Layers

The outer protective layer is the cuticle, the middle layer containing pigment is the cortex, and the inner core is the medulla.

Scale Patterns

The three types of scale patterns are coronal, spinous, and imbricate, which is the pattern found in humans.

Medullary Index Formula

The medullary index is calculated by dividing the medulla diameter by the total hair diameter.

Human vs. Animal Index

Human hair typically has a medullary index less than {0.33}, while animal hair is usually greater than {0.5}.

Hair Growth Rate

The average rate of hair growth is approximately {1\text{ cm}} per month.

Transfer Types

Primary transfer involves direct contact, whereas secondary transfer occurs through an intermediate surface.

Fiber Units

The smallest unit of a textile is known as a fiber.

Fiber Categorization

Cotton and silk are examples of natural fibers, while nylon and polyester are synthetic fibers.

Fiber Analysis Tests

A burn test identifies fiber composition by flame, odor, and ash, but it is considered a destructive method because the sample is consumed.

Dye Analysis

Chromatography is a method that separates dye components as they move across paper to analyze fabric dyes.

Evidence Collection

Hair and fiber evidence are