Forensic Examination of Hair

Shengjie Nie Asoc.Prof

Section of Forensic Biology

Hair evidence & criminal investigation

Small hairs can not escape the prying eyes of an expert.

Grows almost everywhere

Naturally shed.

Be left on clothing or scen

e unintentionally / force

OutlineBiology features of hair Introduction

Hair structure

Hair growth

Color & shape

Distribution

Forensic identification Whether the hair-like evidence in question is hair?

Whether the hair originated from an animal or a human?

Individualize a human hair.

body area? damage? Poison?

Biology features of hair

• produced from hair follicle( 毛囊 )

• develop hair follicles during fetal

development （胎儿发育）

• composed of keratin( 角蛋白 )

Introduction

Hair structure

Hair root

Hair shaft

Hair tip

Hair shaft 毛干

cortex 毛皮质 medulla 毛髓

质

cuticle 毛小皮

Hair structure

Hair structure

Medulla 毛髓质

Filled with air

Appears opaque 不透明

Filled with liquid

Appears translucent 半透明

Hair structure

Medulla 毛髓质

Not present in all human hairs

Presence of medulla varies quite a bit: even hair to hair

continuous Interrupted Fragmented

Hair structure

Five regions of a single head hair (from proximal to distal)

Same hair,

different medulla

Hair structure

Ladder like medulla

Uniserial Ladder Medulla Multiserial Ladder Medulla

Hair structure

Lattice like medulla

晶格状髓质

polyhedral-shaped 多面体

Hair structure

Human hair

Be continuous or discontinuous.

Not large,<1/3 the width of the hair shaft

Medulla: important for species identification

cattle

deer

deer

Animal hair

Be continuous.

>1/3 the width of the hair shaft

Specific pattern

Medulla

Hair structure

• spindle-shaped cells

• parallel to the length of the hair

• Embedded with pigment granules

Hair cortex 毛皮质

梭形细胞

Hair structure

Uniform distribution Peripheral distribution

One-side distribution Central distribution

Pigment distributionHair structure

Human hairGreater than medulla, >1/3

Distribution of pigment: even, slightly

more towards cuticle

Animal hairLess than width of medulla,<1/2

Distribution of pigment: Central or denser towards medulla

Cortex

Hair structure

Hair cortex 毛皮质

The cortex varies in:

• Thickness

• Texture

• Color

Important for matching.

纹理

Hair structure

Hair cuticle 毛小皮

•outer layer of the shaft•overlapping scales

•Characteristic:–How many are there per centimeter –How do they overlap–Its overall shape –Its thickness– Whether or not it contains pigment.

Important in species distinguishing

Hair structure

Coronal Scales冠状鳞片

Bat/some other rodent 啮齿类

Spinous Scales

棘状鳞片 Cats, seals and mink

Bat 蝙蝠 Mink 水貂

Scales are triangular in shape and tend to lift away from the hair at their tips

Hair structure

Imbricate Scales 叠瓦状鳞片

Human Scale Pattern

---flattened scales

Hair cuticle

Hair structure

Human Hair Vs. Animal Hair

Human Hair Vs. Animal Hair

Curticle, cortex and medulla

Hair root 毛根

Hair root

Hair bulb 毛球

hair follicle 毛囊

Hair papilla 毛乳头

Hair structure

Hair tip

Hair root

Hair shaft

cuticlecortexmedulla

bulbfolliclepapilla

Hair Growth 毛发生长

Anagen Phase

生长初期 Catagen Phase

生长中期

Telogen phase

生长终期

Anagen Phase 生长初期

High metabolic and mitotic activity; 2-6 years

Follicle re-forms.

Need a strong pull to detach them from the papilla.

Roots : appear fleshy, sometimes with pigmentation.

Sheath tissue may be attached.

Sheath 毛根鞘

Catagen Phase 生长中期

The inner root sheath begins to disintegrate 蜕变 .

Melanin 黑色素 production stops.

The hair gradually stops growing ； 2 to 3 weeks.

Hairs stay attached to the remains of the follicle

Appears brush-like but with no sheath adhering

No sheath

Telogen phase 生长终期

Follicle is very short , the papilla is separated.

Mitotically inert and contain less DNA.

Lasts for 3-4 months.

No sheath attached, little or no pigment.

Telogen finishes when a new anagen phase commences.

Hair color & hair shape

Influenced heavily by genes.Intentional alteration (perming 烫 /dyeing) can affect the physical appearance

The distribution of hair 毛发分布

Except for the lip, palm, footplate, finger and toes.

The body area determined by

the length, shape, color, stiffness, curliness, microscopic

appearance.

continuous double medulla trace medulla,soft

Beard 胡须Limb 腿毛

Pubic 阴毛

Stiff , curl

A B CC

Which is human Hair ?

Which is human Hair ?

A

B

C

DB

Naturally shed hairs, Undamaged, club-shaped roots.

Forcibly removed hairs

Tissue attached

Forcibly removed hairs

Exhibit stretching and damage to the root area

Anagen Phase Catagen Phase Telogen Phase

Which phase? Naturally shed or Forcibly removed?

A B C