Impressionsshoes, tires, lips, teeth

Types of Impressions

Patent – visible – 2D impressions

Latent – hidden to the eye but can be revealed

Plastic - 3D impressions

Shoe Impressions

Information from Shoe Impressions

Size of the foot!

Depth – determine weight

Type of shoe – job or personality

Brand – money

Sole – manufacturer

Shoeprints

Class - manufacturer, type, model, size

Individual - wear patterns, nicks, marks, outsoles

Shoe Wear Patterns Walks on heels or toes

Body weight

Walks straight ahead or walks with toes pointed inward or outward

Shape of the foot

Wear’s activities

Surface they usually walk on

Unique markings

Gait and tracks

Numerous prints together – gait or walking habits

Limp, injury or carrying a heavy weight – asymmetrical gait

Walking or running – length of stride, pressure and shape

Trail movements/recreating events – sequence Direction Point of entry & exit Mode of entry

Shoeprints at a crime scene

Photo of suspect’s shoes

Collecting Shoe Impression Evidence

1. Photograph

2. Lift latent impressions When a shoe or barefoot walks on a smooth surface it leaves a print Luminol Dusting Gel lifting

Thick layer of gel sandwiched bw paper backing and plastic cover sheet It is thick and flexible 1st dusted with powders then gel is pressed over print – bc its not sticky it

can be used on papers Electrostatic lifting

Applying an electrostatic charge on apiece of lifting film – the film picks up and holds the dust

By viewing the film with a special light source- print made visible

3. Cast plastic impressions Sand or dirt - Plaster of Paris Snow – sprayed with wax – then Plaster of Paris

OJ Simpson Case

JonBenet Ramsey

Tire treads and Impressions

Anatomy of a Tire

Ridges and grooves Channel water away and provide

traction Every model of tire is unique Width and angle of grooves – modified

Tread patterns are symmetrical

Impression – ink painted on tire – driven over paper for 3 meters

Identifying Vehicles Same type of tire

on many vehicles

Need track width and wheelbase Track width –

measured from the center of each tire to the center of the opposite tire (front and rear may differ)

Wheelbase – distance between the center of the front axle and the center of the rear axle

Turning Diameter

Measure of how tight a circle can be driven by a vehicle

Determining Movements from Tire Marks

Disturbed grass or vegetation

Debris patterns

Splash patterns – puddle

Substance transfer

Tire marks

Accident Reconstruction

What happened

When it happened

Where it happened

Why it happened

How fast vehicle was driving

Direction of cars

Who was involved/at fault

Types of Tire marks Skids marks

Brakes suddenly Locked wheels Calculate velocity from skid marks

Yaw marks Produced when a vehicle travels in a curved path

faster than the vehicle can handle and skids sideways Tires and road surface melt from extreme temps Often smoke occurs

Tire scrubs Damaged or overloaded tires after impact Usually curved Determine area of impact

Lip prints

Types of Lip prints

Lip print case study

A bank robber was startled by an alarm just as the teller handed her the money. She grabbed it and, in her haste to get away, ran smack-dab into a glass door. Nevertheless, she recovered and got away. Subsequent examination of the door revealed a red lipstick imprint of the perpetrator’s mouth. Police later picked up a suspect, but needed evidence to link her to the robbery. Are lip prints unique enough to tie the suspect to the crime?

Bite marksConsidered individual evidence

photographed

Individuality Number

Size

Coloration

Alignment

Unique filings

Crowns

Caps

Distance between teeth

Overall condition of teeth

Bite marks

Result from assault or sexual attack, common in domestic violence