Hair Analysis, Day 2

Recap

•Hair can be considered both class and individual evidence depending on if the follicle is present.
•The follicle is the part of the hair that contains DNA.
•The other part of the hair is called the shaft and is composed of 3 layers:

•Cuticle
•Cortex
•Medulla

Recap

•Macroscopic properties of hair include characteristics that can be seen with the naked eye. What are some macroscopic properties?

•Microscopic properties of hair include characteristics that must be seen with the aid of a microscope. What are some microscopic properties of hair?

Match

Match the following!

• Macroscopic

• Microscopic

• Hair Follicle

• Hair Shaft

seen with the eye

see with a microscope

location of DNA on hair

Has 3 layers- cuticle, cortex, medulla

• seen with the eye

• see with a microscope

• location of DNA on hair

• Has 3 layers- cuticle, cortex, medulla

Recap

•There are 5 possible medulla patterns:

Introduction

•Today, we will be
discussing other properties of hair as well as how the medulla can be used to match suspect hair samples to evidence hair samples.

Hair Regions

•Human hairs can vary from region to region
on the body of the same person.
•Hairs originate from:

•Head
•Eyebrow/lash
•Beard
•Pubic area
•Body
•Underarm

Hair Differences

•Hairs can vary from one source to another.
•For example, different ethnic groups have unique characteristics in the properties of their hair.
•Hair examiners have identified some key physical characteristics that are
associated with hair of different ancestral groups: European, Asian, and African.

Hair Differences

•Animal hair and human hair have several differences as well.

• Pigmentation
• Medullary index (we’ll discuss this at the end of the lesson)
• Cuticle type

Hair Differences

Medullary Index:

•The ratio of the diameter of the medulla to the diameter of the entire hair is known as the medullary index.
•If the medullary index is 0.5 or greater, the hair most likely is animal hair
•If the medullary index is 0.33 or less, the hair most likely is human hair

MI= Width of Medulla
Diameter of Hair

Open Ended

MOST LIKELY: If MI is greater than 0.5 it is animal hair, and if it is less than 0.33 it is human hair...

What if it is 0.34-0.49????

Practice

•Suppose this sample of hair has a diameter of 110 microns and has a medulla that measures 62 microns.

•What is the medullary index of hair?
•Is it human or animal?

MI= Width of Medulla
Diameter of Hair

MI= 62
110

Practice

•Suppose this sample of hair has a diameter of 110 microns and has a medulla that measures 62 microns.

•What is the medullary index of hair?
•Is it human or animal?

MI= Width of Medulla
Diameter of Hair

MI= 62
110

MI= 0.56

Dropdown

If the Medullary Index is 0.56, the hair is mostly likely​

Select answer

Practice

•Suppose this sample of hair has a diameter of 110 microns and has a medulla that measures 62 microns.

•What is the medullary index of hair?
•Is it human or animal?

MI= Width of Medulla
Diameter of Hair

MI= 62
110

MI= 0.56

Animal

Hair

Structure of Hair

•Hair is incredibly strong, thanks to the protein that comprises it (keratin)
•Keratin is a chain of amino acids that forms a spiral or helix.
•Keratin helices are connected by strong bonds between the amino acids.
•These bonds also make hair resistant to decomposition, which is extremely useful to forensic investigators.

Hair Analysis in Forensics:

•Forensic lab analysts use a variety of methods for analyzing hair.
•Hair is collected by plucking, shaking and scraping surfaces.
•Adhesives are also used to collect hairs from victims or objects.
•The hair can then be analyzed using microscopy (microscope) or chemical testing.

Hair Analysis in Forensics:

•When using microscopy, investigators use a comparison microscope to make comparisons between the medullary index of a suspect hair and evidence hair.
•Electron microscopes provide remarkably detailed views of a hair sample by magnifying up to 50,000 times.

Hair Analysis in Forensics:

•Anything ingested or absorbed through your skin becomes part of your hair.
•This has proven to be beneficial for forensic investigators.
•Since hair does not readily decompose, tests can help establish a timeline of a suspect’s or victim’s exposure to toxins or drugs.

Ex. Napoleon Bonaparte

Hair Analysis in Forensics:

•A test called Neutron Activation Analysis can be used to detect toxins/chemicals within the hair
•This test can provide links between hair evidence and the circumstances surrounding the hair
•NAA was the nuclear test that was performed on Napoleon Bonaparte’s hair

Hair Analysis in Forensics: