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  • Can be both individual and class evidence
  • Shoe - plastic or dirt Barefoot – oils from body
  • A 19 year old female homicide victim was found in a motel room after an argument with her estranged boyfriend. She was observed at autopsy to have a bitemark on her left shoulder. The dental signature of the perpetrator was clearly evident, including some unusual dental characteristics; namely, an absent bruise where the maxillary right canine should have been, and what appeared to be five lower incisors.

Impressions Impressions Presentation Transcript

  • Impressions shoes, tires, lips, teeth
  • Types of Impressions Patent – visible – 2D impressions Latent – hidden to the eye but can be revealed Plastic - 3D impressions
  • ShoeImpressions
  • 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 treadsandImpressions
  • 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 evidencephotographed
  • 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