Dental and Tool impressions

Impressions

Types of Impressions

  • Patent Impression:

    • Two-Dimensional (2-D) impressions that are clearly visible.

  • Latent Impression:

    • Hidden impressions requiring special techniques to become visible.

  • Plastic Impression:

    • Three-Dimensional (3-D) impressions cast in soft materials (e.g., soil, snow, or blood).

Forensic Odontology

Overview

  • Odontology: The study of the anatomy and growth of teeth and diseases of teeth and gums.

  • Role of Forensic Odontologists:

    • Identify victims in mass disasters.

    • Assist police in criminal investigations.

    • Verify signs of abuse.

History of Forensic Dentistry

  • Use of dental examination dates back to:

    • 66 AD: Roman Emperor Nero’s mother Agrippina checked front teeth discoloration for identification.

    • Post-WWII, it was used to verify remains of Adolf Hitler and Eva Braun, and in the identification following the 9/11 attacks.

Teeth & the Body

  • Teeth follow a semi-standardized pattern of aging.

  • Unique Characteristics:

    • Individual sets of teeth in humans.

    • Teeth are composed of enamel, the hardest tissue in the human body, capable of withstanding decay and trauma due to decomposition.

Estimating Characteristics

  • Ancestry Determination:

    • Physical characteristics cannot definitively determine ancestry.

  • Gender Determination:

    • Males usually have larger, broader teeth.

    • Females generally have pointed canine teeth.

  • Age Determination:

    • Age estimation is most accurate based on the pattern of teeth shedding from childhood to adulthood.

Development of Teeth

  • Teeth Timeline:

    • Central Incisor: 6-8 years.

    • Lateral Incisor: 7-8 years.

    • Canine (Cuspid): 10-12 years.

    • Premolars: 10-12 years.

    • Molars: vary by type, generally 6-12 years.

    • Third Molar: Emerges between 17-21 years.

Bite Mark Evidence

  • Importance of Analyzing Bite Marks:

    • Identify victims/suspects.

    • Can leave marks on skin or objects (e.g., Styrofoam, gum).

    • Saliva or blood left behind can be tested for DNA.

  • Dental Records:

    • Useful for victim identification; includes x-rays and other dental documentation.

Human Bite Marks

  • Differences in Bite Marks:

    • Appear differently in soft substances (e.g., skin) vs. hard substances (e.g., cheese).

  • Analysis:

    • Color can indicate how long ago the bite occurred.

    • Ante Mortem: Area bruises/swells.

    • Post Mortem: Area shows no swelling.

  • Typical bite shape: double horseshoe pattern, common on sexual assault victims.

Collecting & Analyzing Dental Evidence

  • Documentation:

    • Photographing with a scale for size reference.

  • Swabbing bite marks for DNA evidence, collecting saliva/blood separately.

Using Dental Evidence

  • Applications in forensic investigations:

    • Identify remains.

    • Profile unique bite patterns.

  • Comparison Points: 76 points of comparison when matching dental patterns.

The Most Famous Bite

  • Ted Bundy: Noted for an infamous case of bite mark evidence.

Characteristics of Dental Impressions

  • Type of Evidence:

    • Circumstantial/indirect, physical, individual.

  • Type of Impression: Plastic.

Tool Mark Evidence

Introduction

  • Definition: Any impression, abrasion, or cut from contact between a tool and an object.

  • Considered class evidence due to mass production, but individual tool marks can have unique identifiers.

Types of Tool Marks

  • Indentation Marks:

    • Result from a tool pressing against a softer surface; often leave distinctive marks.

  • Abrasion Marks:

    • Worn away material from a surface; hardness of tools influences damage.

  • Cutting Marks:

    • Created by edged tools penetrating and separating softer objects.

Tool Mark Examination

  • Specialists analyze tool mark evidence, gathering impressions and investigating recovered tools.

  • Documentation: Include size measurements, photographs, and potentially the entire object if the mark is found on it.

New Technology in Tool Mark Identification

  • Courts require evidence beyond visual comparisons:

    • Tool mark databases and algorithms for statistical analysis.

    • Scanning tools can measure the depth or height of impressions.

Presentation in Court

  • Tool mark experts prepare reports presenting evidence to juries with original items, castings, and magnified images for clearer comparisons.