Trace Evidence: Hair Forensic Science.

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Forensics of Hair Analysis

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Presentation transcript:

Trace Evidence: Hair Forensic Science

Structure Cortex – the main body (wooden portion) Medulla – the central cell of the cortex that is not always present in every hair (lead) Cuticle – a layer of scales covering the hair shaft (yellow paint) Pencil vs. Hair Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Structure (continued) Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Types of Medulla Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Roots Hairs that are forcibly removed often end up with a follicular tag (a soft tissue from the follicle) attached to the roots. The follicular material may be suitable for nuclear DNA analysis. telogen root without follicular tag telogen root with follicular tag Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Stop and Talk Take 90 seconds to talk with you table members about what use do you think hair analysis can provide in the case of identical twins?

Roots (continued) Postmortem Root Band (aka "Dead man's root”) a dark band that may appear near the root of the hair originating from a decomposing body Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Human & Animal Hair Human Animal Medulla Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Scales Imbricate Scales Human Imbricate Scales Coronal Scales Diagram Bat Hair Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

More Examples Spinous Scales Diagram Mink hair Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Human & Animal Hair 3 Main differences Human Hair Animal Hair Pigment remains constant in its color and pigmentation throughout the length of the shaft often exhibits rather rapid and radical color changes Medulla thin, taking up no more than 1/3 of the hair shaft diameter; amorphous very wide; its structure is very regular and well-defined (with certain patterns) Scale Structure has overlapping imbricate (flattened) scales with narrow margins some have coronal (crown-shaped) scales or spinous (petal-shaped) scales Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Hair Comparisons Comparison microscope 2 compound microscopes connected together with an optical bridge Enables side-by-side comparisons Typical magnification from 100X to 250X Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Hair Comparisons (continued) Information NOT provided by a hair examination Age Gender Unless nuclear DNA analysis is performed on its follicular tag Information provided by a hair examination Is it human or animal hair? What is the possible race of the donor? What area of the body did it come from? Hair can also be used to distinguish between identical twins (who cannot be distinguished based on their DNA). because of the environmental effects on hair such as weather exposure, diet, artificial treatment, etc. Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.

Significance of Hair Evidence The frequency of contact between a victim and a suspect, as well as the crime scene, is a big factor in interpreting the significance of hair evidence. Examples The pubic hair of a recent ex-boyfriend found at the scene of a sexual assault A husband who is suspected of murdering his wife at home A missing child's hair in the backseat of a former nanny's car A missing child's hair in the backseat of a cleaning lady's car A stepfather's head hair found on a little girl's underwear A stepfather's pubic hair found in the crotch area of a little girl's underwear Copyright © Texas Education Agency 2011. All rights reserved. Images and other multimedia content used with permission.