Forensic Examination of Hair
Shengjie Nie Asoc.Prof
Section of Forensic Biology
Hair evidence & criminal investigation
Grows almost everywhere
Naturally shed.
Be left on clothing or
scene unintentionally / force
Small hairs can not escape the prying eyes of an expert.
Outline
Biology
Biology 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?
Introduction
• produced from hair follicle(毛囊)
• develop hair follicles during fetal
development（胎儿发育）
• composed of keratin(角蛋白)
Hair structure
Hair tip
Hair shaft
Hair root
Hair shaft
cortex 毛皮质
cuticle
毛干
medulla 毛髓质
毛小皮
Hair structure
Hair structure
Medulla 毛髓质
Filled with air
Filled with liquid
Appears opaque 不透明
Appears translucent 半透明
Hair structure
Medulla 毛髓质
continuous
Interrupted
Fragmented
Not present in all human hairs
Presence of medulla varies quite a bit: even hair to hair
Hair structure
Same
hair,
different
medulla
Five regions of a single head hair (from proximal to distal)
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
Hair structure
Human hair
Be continuous or discontinuous.
Not large,<1/3 the width of the hair shaft
Medulla
Animal hair
Be continuous.
>1/3 the width of the hair shaft
Specific pattern
cattle
d
e
e
r
deer
Medulla: important for species identification
Hair cortex 毛皮质
• spindle-shaped cells 梭形细胞
• parallel to the length of the hair
• Embedded with pigment granules
Hair structure
Hair structure
Pigment distribution
Uniform distribution
One-side distribution
Peripheral distribution
Central distribution
Human hair
Greater than medulla, >1/3
Distribution of pigment: even, slightly
more towards cuticle
Cortex
Animal hair
Less than width of medulla,<1/2
Distribution of pigment: Central or
denser towards medulla
Hair structure
Hair cortex 毛皮质
The cortex varies in:
• Thickness
• Texture
纹理
• Color
Important for matching.
Hair structure
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
Bat 蝙蝠
Spinous Scales
棘状鳞片
Cats, seals and mink
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
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 shaft
cuticle
cortex
medulla
Hair root
bulb
follicle
papilla
Hair Growth 毛发生长
Anagen Phase
Catagen Phase
Telogen phase
生长初期
生长中期
生长终期
Anagen Phase
生长初期
Sheath 毛根鞘
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.
Catagen Phase 生长中期
No sheath
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
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
Pubic 阴毛
Beard 胡须
continuous double medulla
Stiff , curl
Limb 腿毛
trace medulla,soft
 Except for the lip, palm, footplate, finger and toes.
 The body area determined by
the length, shape, color, stiffness, curliness, microscopic
appearance.
Which is human Hair ?
A
B
C
Which is human Hair ?
A
C
B
D
Which phase? Naturally shed or Forcibly removed?
A
Catagen Phase
Forcibly removed hairs
Tissue attached
B
Anagen Phase
Forcibly removed hairs
Exhibit stretching and
damage to the root area
C
Telogen Phase
Naturally shed hairs,
Undamaged, club-shaped
roots.