Forensic examination of hair

Forensic Examination of Hairs

Bhoopendra Singh BhaskarM.Sc. Forensic Science 1st Semester Bundelkhand University, Jhansi

Hair is a filamentous biomaterial that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of mammalian class. Hair have a structure consisting of several

layers:-a) Cuticleb) Cortex c) Medulla

Introduction of Hair

Cuticle is outer layer of the hair shaft.

It consist of several layers of flat, thin cells without over-lapping one another.

Hair StructureCuticle

Cortex

The region of a hair located between cuticle & medulla layer containing pigment granules known as Cortex.

Hair Structure

MedullaIt is the central part of the hair, made

up of large loosely connected cells which contain Keratin.

Sometimes  medulla may be absent in some species.

On the basis of appearance of medulla it is divided into five types:-

1) Continuous2) Interrupted3) Fragmented4) Solid5) Absent

Hair Structure

Human Hair :- Different Sites

Scalp Pubic Vulvar Chest Beard Axiliary

Eyebrow Eyelash Nose Limb Buttocks

Feature Human Hair Animal Hair

Cortex The width of cortex greater than medulla

Usually less than width of medulla

Distribution of pigment Towards cuticle Central or denser towards medulla

Medulla Medulla dis-continuous Medulla continuous

Scales Imbricate Coronal, ring form

Differences between Human & Animal Hair

Sampling Of Hair Spread the exhibit on a clean white surface under proper

illumination. With hand magnifier, carefully locate any loose hair and

collect. Hair can be collected by forceps or transferred to adhesive

tape. Samples collected should be packed in cellophane or paper

folders with proper labeling on them. Root bulb and follicle of hair should be carefully preserved

for determination of sex , serological and DNA Examination.

Examination Of Hair

Temporary Mount

Scale Casting

Cellulose Acetate Method

Polaroid Coater Method

Permanent Mount

Cross Sectionin

g

Micrometry

Temporary Mount

Make a temporary mount of the hair sample on a clean slide with the distilled Water or glycerin. Cover with cover slip.

Observe morphological characteristics under microscope.

Scale Casting

Cellulose Acetate Method

Polaroid Coater Method

On a clean microscopic slide, place a thin layer of cellulose acetate paste with low viscosity.

With fine forceps, place hair on to the cellulose acetate paste and press with another clean slide.

Allow it to dry for 2-5 min.Observe scales of hair under microscope.

Cellulose Acetate Method

Polaroid Coater Method

Place the hair on a clean microscope slide, securing the ends with cellophane tape.

Using a Polaroid film coater, make 2 or 3 passes along the length of the hair.

Allow the coating to dry for 23 hours. After removing the cellophane tape, gently peel the hair

from the slide. With a sharp scalpel, slice away the excess coating

protruding above the flat surface of the scale cast. Observe the scale impressions microscopically.

Permanent MountPlace hair on slide in a

drop of xylene and add permanent mounting medium.

Place a cover slip on the hair allowing the medium.

Label the slide appropriately and allow it to dry for 48 hours.

Cross Sectioning

Clean hair in solution of ether and ethanol in ratio 1:1 Bundle the samples and dip in a block of molten wax

and allow to cool. Cross sections can be taken either with a sharp blade

or with a microtone to a thickness of 5-10 microns. Place sections on a clean slide and dissolve wax with

a drop of xylene. Prepare permanent mount of the sections and examine

under the microscope.

Micrometry

With the help of micrometer measure following distances & calculate different indices:

Maximum diameter of the shaft. Number of scales per unit length. Diameter of hair in microns / scale

count. Maximum diameter of hair medulla

/ Maximum diameter of hair shaft. Minimum diameter of shaft /

Maximum diameter of the shaft x 100

Report Writing

Species of Origin On the basis of morphological examination

Sex On the basis of microscopic examination

Site On the basis of morphological examination

Comparison On the basis of morphological examination