Trace Evidence

Forensics Class ILHS Unit 7: Trace Evidence

Why do mammals have hair?

• To regulate body temperature

• Decrease friction/chafing

• Protect against sunlight

• Can be sensory organs (like whiskers for cats)

What is the Folicle/Root?

The club-shaped potion embedded in the skin, where blood vessels are connected and where the DNA is found

In a hair, where is the DNA?

Follicle/Root is the bulb part of the hair, it’s where the hair grows from and where the DNA is

What is the Shaft of Hair?

The hair shaft is the non-growing dead portion that portudes from the skin. It’s made of Keratin, which makes it strong and flexible.

What is Keratin and what is it for?

Keratin is the protein that makes the shaft strong and flexible

The shaft is composed of what three parts?

Cuticle, the outside part that has a texture

Cortex, the inside part that has pigment

Medulla, the inner string, like pencil led, that can be used to identify if it’s human or not

What is the cuticle?

Cuticle is the outside of the hair, it’s the textured outside part. Humans have imbricate pattern (like dogs). Think like nail cuticle, the thin skin layer that goes on top of nails.

What is the Cortex?

Cortex is the inside part, it contains the pigment

What is the medulla?

The medula is the very inside part of the hair. It can be continuous, interupted, fragmented or segmented, solid, or even no medulla at all.

What pattern of cuticle do humans have?

The cuticle is tranparent and protects the other layers. Humans have imbricate pattern.

What is the cortex made of? What does it contain?

The cortex is made of Keratin and contains pigment, melanin.

Using the medulla, how can you tell if a hair is human or not?

Human hairs have medullas that are less than 33% medulla

What is the Medullary Index? (MI)

The ratio of the diameter of the medulla to the entire diameter of the hair.

MI = diameter-of-medulla / diameter-of-hair

What are the cross section types of hair and what do they mean?

• Round (straight hair)

• Oval (curly hair)

• Crescent moon (kinky or wavy hair)

How thick is the diameter of hair?

Diameter of hair is 15-125 micrometers (mew m)

What is the hair growth cycle?

1. Anagen (growth phase)

   Nourishment of the hair folicle via blood supply enables growth

2. Catagen (transition phase)

   Hair folicle detaches from blood supply

3. Telogen (resting phase)

   Without nourishment, hair dies and falls out

Remember as Anakin grew up to kill cats and fall into lava pits.

What is the anagen state and how long does it last?

• Anagen stage is active growth

• Hair grows 1.3 cm per month

• This stage lasts 2-6 years, and about 80-90% of hair is in this stage.

What is the Catagen Stage, and how long does it last?

• Catagen stage is transition stage where the follicle starts to degenerate

• This lasts 1-2 weeks

• 2% of hair is in this stage

What is the Telogen Stage and how long does it last?

• Telogen stage is growth stops completely, the follicle is dormant/resting

• It lasts about 2-4 months

• 10-18% of hair is in this stage

How many hairs do you lose per day?

50-100

What does bleaching do to hair?

• Removes pigment moleculesd from hair

• leaves hair yellowish

• makes hair brittle

• disturbs scales on cuticle

What does dying do to hair?

• changes the colour of the hair shaft

• Cortex and cuticle affected

How can you tell how long ago someone changed their hair colour?

Measure length of natural hair roots in cm

divide by growth rate (1.3 cm / month)

Determine number of months since colour change

What is Questioned Hair and what is exemplar hair?

• Questioned hair: Comes from crime scene

  It’s first checked which speceis, then if it’s human, its charactaristics are compared to the suspect pool

• Exemplar hair is from a suspect, for example

What can Hair tell us?

• What species

• Racial origin (sometimes)

• Location on the body

• Whether it has been chemically altered (dyed, bleached)

• When particular drugs were used over a long period of time

• Metal content (can diagnose dietary deficiencies and diseases)

What can hair NOT tell us?

• Sex

• Age

What is a fiber? Where could fibers come from?

A fiber is the smallest unit of a fabric

It must be at least 100 times longer than wide

it comes from:

• carpets

• clothing

• linens

• furniture

• insulation

• rope

• etc

Fibers are spun together to make ______ which is weaved together to make _______

Fibers are spun together to make yarn which are weaved together to make textiles and fabrics

Fibers are used to make:

• Textiles (clothes, carpets)

• Cordage (rope, string, nets)

• brushes

• Optical cables

• structural materials

What are some examples of natural fibers?

Vegetable

• Jute

• Hemp

• Sisal

• Bamboo

Animal (looks like hairs, it is hair)

• Wool

• Silk

• Mohair

• Alpaca

Mineral

• Asbestos

• Fiberglass

What are some examples of Man-Made fibers?

Natural Polymer

• Milk Fibre

Synthetic

• Nylon

• Acrylic

• Acetate

• Spandex

Animal fibers are made of _______, while plant fibers are made of _________

Animal fibers are made of protein, while plant fibers are made of cells

Synthetic fibers are either regenerated (_____+______) or Synthetic polymers (________)

Synthetic fibers are either regenerated (Plants+chemicals) or Synthetic polymers (petroleum/plastic)

What is Warp in a textile weave? What is Weft?

Warp is lengthwise, up and down, the stretched set of yarns that the other yarns are weved through. It’s stronger types of fibers.

Weft (remember as “left“) is crosswise. usually weaker fibers

How are fibers gathered?

vacuums, sticky tape, and forceps then put into a bindle

What is an example of a destructive test?

• Bleach test

  Look for colour change, bubbles, or material dissolving

• Burn Test

  Does it burn or melt? Shrink from flames? Odors? Residue left?

What is Spectroscopy?

• Emits a beam of light that bounces off fibers and returns to the instrument

• Depending on changes in the beam, the chemical structure can be determined

What is an example of a 2D forensic impression? What about 3D?

2D: Fingerprint (patent or latent)

3D: tool marks, marks bullet caused, creates plastic imprint

What is an example of Pattern Evidence?

• Shoe marks

• tire marks

Pattern evidence can identify a brand, model, or size

Can identify tread wear, cuts, or nicks

What can shoeprints tell you?

• Brand

• Model

• Size

• Foot length

• Height

• Stride length

• Tread wear, cuts, nicks

What are some examples of impression evidence?

1. Fingerprints

2. Bite Marks

3. Footprints

4. Tire marks/tracks

5. Tool marks

Is a tool mark a class or individual evidence?

Both.

Tool mark is class becuase it can be traces back to a specific tool

It could become individual through the presence of any minute imperfections or patterns from the life of the tool.

What are the types of tool marks?

• Compression/indentation

  When a tool is pressed into soft surface (can show size and shape of tool)

• Abrasion/Striation

  When a tool slides along a surface. (Can narrow down type of tool, or give individual evidence in working edge)

• Combination

  Pressed and dragged

• Cutting marks

  Sharp edge cuts something into parts

What is Striation (Abrasion)?

The mark left when a tool slides along a surface. (Can narrow down type of tool, or give individual evidence in working edge)

How do you collect tool mark evidence?

1. Observe, measure, describe

2. Photograph perpendicular to toolmark in oblique lighting with ruler

3. Cast made

   1. if the support where the toolmark was made cant be collected as evidence

How do you collect tool evidence?

1. Observed and photographed

2. Working end covered in cloth and boxed and brought back to lab

3. Comparison tool-marks are made on soft material like clay or lead so extra marks are not created

4. Comparison microscope is used to compare (one eye in mystery mark, one eye in tool mark, trying to line it up)

5. If a match is made, common origin is established

How many teeth do adult humans have?

32. 8 different types.

16 on top jaw (maxilla), 16 on bottom jaw (mandible)

What are the 8 types of teeth?

1. 3rd molar (wisdom teeth)

2. 2nd molar

3. 1st molar

4. 2nd premolar

5. 1st premolar

6. canine

7. Lateral incisor

8. central incisor

What is the strongest substance in your body?

Enamel is the strongest substance your body makes. Teeth are made of dentin and enamel.

What are your teeth made of?

Dentin and enamel. Tooth enamel can outlast bone and withstand heat up to 2,000 degrees F.

What are forensics odontologists? What do they do?

Forensic Odontologists identity human remains by their dentition (teeth).

They study dentation of dead people and compare them with dental records. They look at things like location and shapes of fillings, root canals, crowns, tooth positions, and more to find a match.

What are some examples of when teeth can be used to identify bodies?

• Mass disasters like earthquakes, tsunamis, plane crashes

• Disfigured bodies (drowning, fire, bombs)

• Decomposed bodies

Where can bite marks be found?

• On a victim that was bitten by suspect

• On a suspect that was bitten by victim

• On objects suspects or victims have bitten and left at crime scene

Odontologist will study and try to find a match.

What happens when skin is bitten? What are the 3 stages?

Stage 1:

• Immediately after a bite

• Forms an impression or indentation

• Lasts 1-10 minutes

Stage 2:

• Area swells with inflammation

• Obscures individual tooth marks

• Lasts several hours

Stage 3:

• Final state

• Bruising

What are the bite mark scales? Which are most valuable to forensic odontologists?

Least severe: Level 1

Most Severe: Level 2

Level 3 and 4 are most valuable:

• Obvious bite mark

• bruising or lacerations

How do you collect bite mark evidence?

• Take a photo with rulers and capture much of the mark as possible, different lighting

• Make a cast

How do you collect a bite impression?

• Obtain warrant to collect bite impression

• Bite into soft wax

• 3D mold

How do you use an overlay in bite mark comparison?

Put sheet of plastic over the bite impression or teeth mold, then trace tooth locations with a marker.

Then, place the overlay on a photo or cast of bite mark to find similarities or difference sin tooth placement and angle.

What are accidental characteristics?

Identifying characteristics made by every day wear and tear, cuts, nicks, dings, and scuff marks.

What is stride length? How do you measure it?

Taller = longer stride length

MEASURE FROM HEEL TO HEEL!