trace elements: hair as evidence. review of locard’s principle edmond locard established the...

TRACE ELEMENTS: TRACE ELEMENTS: HAIR AS EVIDENCEHAIR AS EVIDENCE

Review of Locard’s PrincipleReview of Locard’s Principle

Edmond Locard established the Exchange Edmond Locard established the Exchange Principle which states that when two Principle which states that when two objects come into contact with each other objects come into contact with each other material will be exchanged.material will be exchanged.This material is generally collected from This material is generally collected from the exchange object. For example, a hair the exchange object. For example, a hair collected off of a chair.collected off of a chair.This type of evidence is called trace This type of evidence is called trace evidence.evidence.

Trace EvidenceTrace Evidence

Trace evidence is a Trace evidence is a category of physical category of physical evidence.evidence.

Examples of trace Examples of trace evidence include: evidence include: hairs, fibers, hairs, fibers, fingerprints, paint fingerprints, paint chips, soil, sand, chips, soil, sand, gunshot residue and gunshot residue and dust.dust.

Hair as EvidenceHair as Evidence

Human hair is one of the most frequently found Human hair is one of the most frequently found pieces of evidence at the scene of a violent pieces of evidence at the scene of a violent crime. It can provide a link between the criminal crime. It can provide a link between the criminal and the act.and the act.

From hair one can determine:From hair one can determine: Human or animalHuman or animal RaceRace OriginOrigin Manner in which hair was removedManner in which hair was removed Treated hairTreated hair Drugs ingestedDrugs ingested

The First Determination for Hair The First Determination for Hair Evidence: Human or Animal?Evidence: Human or Animal?

In order to make In order to make the determination the determination human vs. animal, human vs. animal, an understanding an understanding of the morphology of the morphology of hair and types of of hair and types of hair is essential.hair is essential.

Hair MorphologyHair MorphologyThe Study of Structure and FormThe Study of Structure and Form

Parts of the hairParts of the hair Shaft--part of the hair Shaft--part of the hair

that that

sticks out of the skinsticks out of the skin

Root--lies below Root--lies below

the the

epidermisepidermis

Follicle—organ from Follicle—organ from

which which

the hair grows (source the hair grows (source

of DNA)of DNA)

A Pencil Analogy for the Three A Pencil Analogy for the Three Layers of HairLayers of Hair

Hair CuticleHair Cuticle

The cuticle is the The cuticle is the outermost layer of hair outermost layer of hair which is covered with which is covered with scales. scales.

Scales always point Scales always point toward the tip of the toward the tip of the hair. These scales differ hair. These scales differ between species of between species of animals and are named animals and are named based on their based on their appearance.appearance.

Scale TypesScale Types

Mosaic Chevron

Rabbit- Chevron ScalesRabbit- Chevron Scales

Cat- Mosaic ScalesCat- Mosaic Scales

Scale Types (cont)Scale Types (cont)

Imbricate Petal

Human- Imbricate ScalesHuman- Imbricate Scales

Dog- Petal ScalesDog- Petal Scales

Hair CortexHair Cortex

The cortex has two The cortex has two

major components:major components: Melanin--pigment Melanin--pigment

granules that give granules that give hair its colorhair its color

Cortical fusi--air Cortical fusi--air spaces, usually spaces, usually found near the found near the root but may be root but may be found throughout found throughout the hair shaftthe hair shaft

Hair MedullaHair Medulla

The medulla is the central canal running through The medulla is the central canal running through the hair core. A medulla is always present. the hair core. A medulla is always present.

The medulla comes in different types and patterns.The medulla comes in different types and patterns.

Types:Types: ContinuousContinuous

Intermittent or interruptedIntermittent or interrupted

FragmentedFragmented

Absent--not presentAbsent--not present

Hair Medulla PatternsHair Medulla Patterns

UniserialUniserial

MultiserialMultiserial

VacuolatedVacuolated

LatticeLattice

AmorphousAmorphous (without a distinct pattern) (without a distinct pattern)

Medullary IndexMedullary Index

The index measures the diameter of the The index measures the diameter of the medulla relative to the diameter of the medulla relative to the diameter of the hair shaft.hair shaft.

Medullary Index for human hair is Medullary Index for human hair is generally less than 1/3.generally less than 1/3.

For animal hair, it is usually greater For animal hair, it is usually greater than 1/2.than 1/2.

A human medulla may be A human medulla may be classified as absent, fragmental, interrupted, or

continuous.

A Cat Medulla is uniserial and A Cat Medulla is uniserial and generally described as a string of generally described as a string of

pearlspearls

A Rabbit medulla is different depending on A Rabbit medulla is different depending on where the hair grows on the rabbit. Both of where the hair grows on the rabbit. Both of

these hairs are from the same rabbit. One is these hairs are from the same rabbit. One is multi-serial and the other two are uniserial.multi-serial and the other two are uniserial.

A Cow medulla has an amorphous A Cow medulla has an amorphous patternpattern

A Deer Medulla has a lattice A Deer Medulla has a lattice patternpattern

Hair RootHair Root

The hair root is the end in the follicle The hair root is the end in the follicle from which the hair grows.from which the hair grows.

The length of hair grows 0.5 mm per The length of hair grows 0.5 mm per day or 1 centimeter per month.day or 1 centimeter per month.

There are three phases for hair:There are three phases for hair:

AnagenAnagen

CatagenCatagen

TelogenTelogen

Anagen PhaseAnagen Phase

The anagen phase is the The anagen phase is the growing phase. This growing phase. This phase may last from 2 phase may last from 2 years to 6 years for a years to 6 years for a given hair.given hair.

Approximately 85% of hair Approximately 85% of hair is in the growing phase at is in the growing phase at any one time.any one time.

During this phase the hair is During this phase the hair is at maximum depth in the at maximum depth in the skin.skin.

Catagen PhaseCatagen Phase

The catagen phase is the The catagen phase is the transitional phase. This transitional phase. This phase lasts one to two phase lasts one to two weeks.weeks.During this stage, the During this stage, the follicle shrinks to 1/6 of its follicle shrinks to 1/6 of its normal length. The normal length. The dermal papilla breaks dermal papilla breaks away to rest below.away to rest below.Blood supply is cut off Blood supply is cut off and the hair stops and the hair stops growing.growing.

Telogen PhaseTelogen Phase

The telogen phase is The telogen phase is the resting phase. the resting phase. This phase lasts This phase lasts about 100 days for about 100 days for scalp hair.scalp hair.At this time the hair is At this time the hair is completely at rest. completely at rest. Anywhere from 25-Anywhere from 25-100 telogen hairs are 100 telogen hairs are normally shed each normally shed each day.day.

The Hair Root The Hair Root

During each of the hair phases, the root During each of the hair phases, the root has a different shape.has a different shape.During the anagen phase the root has a During the anagen phase the root has a flame shape.flame shape.During the catagen phase the root begins During the catagen phase the root begins to elongate and get thinner.to elongate and get thinner.During the telogen phase the root During the telogen phase the root becomes club-shaped and the root becomes club-shaped and the root hardens.hardens.

If a hair is forcibly removed…If a hair is forcibly removed…

Hairs shed normally during the telogen Hairs shed normally during the telogen phase so the root is not effected when the phase so the root is not effected when the hair is shed.hair is shed.However, during the anagen phase, the However, during the anagen phase, the root is bulb shaped and attached to the root is bulb shaped and attached to the follicle. A hair would have to be forcibly follicle. A hair would have to be forcibly removed during this phase. Therefore, the removed during this phase. Therefore, the root will show signs of trauma. This is a root will show signs of trauma. This is a very important clue in violent crimes.very important clue in violent crimes.

Anagen Hair Root from a forcibly Anagen Hair Root from a forcibly removed hair. The root shows signs removed hair. The root shows signs

of the trauma.of the trauma.

Telogen Hair RootNaturally shed hairs display club shaped root. The root does not have any signs of trauma.

Human hair roots are different from Human hair roots are different from animal hair roots.animal hair roots.

Cat Hair RootCat Hair Root

Squirrel Whisker RootSquirrel Whisker Root

Summary of Human vs. AnimalSummary of Human vs. Animal

In order to determine if a In order to determine if a hair is human or animal:hair is human or animal:

1. Compare the hair scales1. Compare the hair scales

2. Compare the medullary 2. Compare the medullary indexindex

3. Compare the medullary 3. Compare the medullary shape/patternshape/pattern

4. Compared the hair root4. Compared the hair root

If the hair is human…If the hair is human…

Once the Once the determination is made determination is made that the hair is human that the hair is human then race, origin and then race, origin and hair treatments can hair treatments can be decided.be decided.

Determination of RaceDetermination of Race

African-American hairs are kinky, containing African-American hairs are kinky, containing dense, unevenly distributed pigments (left)dense, unevenly distributed pigments (left)

Caucasian hairs are straight or wavy with Caucasian hairs are straight or wavy with very fine to coarse pigments that are more very fine to coarse pigments that are more evenly distributed (right)evenly distributed (right)

Origin of Human HairOrigin of Human Hair

Scalp hair shows little diameter variation Scalp hair shows little diameter variation and more uniform distribution of and more uniform distribution of pigment color.pigment color.

Beard hair is coarse and has blunt tips. Beard hair is coarse and has blunt tips.

Pubic hair is short and curly, with wide Pubic hair is short and curly, with wide variation in shaft diameter, or buckling, and variation in shaft diameter, or buckling, and has a continuous medulla. has a continuous medulla.

Colored HairColored Hair

Dyed hair – presence of “color” Dyed hair – presence of “color” in cuticle and throughout cortexin cuticle and throughout cortex

Bleaching – removes natural Bleaching – removes natural pigment and gives yellowish pigment and gives yellowish tinttint

Dyed and bleached hair can Dyed and bleached hair can be determined through be determined through microscopic examination.microscopic examination.

Ingested DrugsIngested Drugs

5-10 days after the 5-10 days after the drug is ingested, it will drug is ingested, it will be present in the hair.be present in the hair.The drug becomes a The drug becomes a part of the hair may part of the hair may be detected up to 2 be detected up to 2 years.years.It takes at least 50 It takes at least 50 scalp hairs for an scalp hairs for an accurate test.accurate test.

Other Types of IdentificationOther Types of Identification

Age - only infant’s hair can be determined Age - only infant’s hair can be determined because it is so fine.because it is so fine.

Sex- sex cannot be determined from hair.Sex- sex cannot be determined from hair. Manner- can determine if hair was forcibly Manner- can determine if hair was forcibly

removed. The follicle tag will still be attached.removed. The follicle tag will still be attached.

Individualization- through positive microscopic Individualization- through positive microscopic comparison and mitochondrial DNA analysis a comparison and mitochondrial DNA analysis a link from questioned hair to standard hair can link from questioned hair to standard hair can be proven.be proven.

Collection of Hair EvidenceCollection of Hair Evidence

Questioned hairs given to the lab for analysis Questioned hairs given to the lab for analysis must be accompanied by an adequate must be accompanied by an adequate number of control samples.number of control samples.– from victimfrom victim– possible suspectspossible suspects– others who may have deposited hair at the sceneothers who may have deposited hair at the scene

The Control Sample should include:The Control Sample should include:– 50 full-length hairs from all areas of scalp50 full-length hairs from all areas of scalp– 24 full-length pubic hairs24 full-length pubic hairs– The full hair is needed so the control samples will The full hair is needed so the control samples will

be pulled out or cut as close as possible to the be pulled out or cut as close as possible to the skin.skin.

Bill Cosby’s sonBill Cosby’s son

Ennis Cosby was stranded on the side of a Ennis Cosby was stranded on the side of a highway due to a flat tire. As Ennis waited highway due to a flat tire. As Ennis waited for help, Mikail Markhasev robbed and for help, Mikail Markhasev robbed and murdered him.murdered him.The police found the murder weapon The police found the murder weapon wrapped in a blue cap. Hair was also wrapped in a blue cap. Hair was also recovered from the cap. Markhasev was recovered from the cap. Markhasev was convicted on the murder based on the hair convicted on the murder based on the hair evidence. He later confessed to the crime.evidence. He later confessed to the crime.