Personal Identification Methods

Personal Identification Methods

Personal Identification Methods

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Fundamentals & Somatometry - Body Basics & Measures

  • Identification: Establishing a person's/remains' individuality.
  • Corpus Delicti: "Body of crime"; proof a crime occurred under BSA evidentiary standards. Vital first step.
  • Somatometry: Systematic measurement of body & parts (foundational method).
    • Anthropometry: Focuses on body measurements for comparison.

    • Modern Priority: DNA analysis, fingerprinting, dental records, CT/MRI imaging supersede traditional methods.

    • Bertillonage (Signalment System):

      • Alphonse Bertillon (1879) - historical significance.
      • Uses 11 body measurements (e.g., height, head length/breadth).
      • Skeletal dimensions fixed post-age 20.
      • Replaced by advanced forensic techniques.
    • Indices: Cephalic ($CI = \frac{\text{Head Breadth}}{\text{Head Length}} \times \mathbf{100}$), Ponderal.

⭐ Will West case (1903) exposed Bertillonage limits: two men, similar measures, distinct fingerprints - validating modern BSA scientific evidence standards.

Dactylography & Prints - Unique Finger Fun

  • Dactylography (Fingerprinting): Science of fingerprint identification.

  • Core Principles:

    • Uniqueness: No two fingerprints are identical (even in monozygotic twins).
    • Permanence: Formed between 10-24 weeks of gestation; remain unchanged throughout life.
    • Classifiable: Patterns allow systematic classification (Henry's system).
  • Types of Fingerprints Found at Scene:

    • Latent: Invisible; require development (e.g., powders, ninhydrin, silver nitrate).
    • Patent (Visible): Made by fingers stained with blood, ink, etc.
    • Plastic (Molded): Impressions on soft surfaces (e.g., wax, soap, putty).
  • Basic Fingerprint Patterns (Frequency):

    • Loops (~60-65%): Ulnar or Radial. One delta.
    • Whorls (~30-35%): Plain, Central Pocket, Double Loop, Accidental. Two deltas.
    • Arches (~5%): Plain or Tented. No delta.
  • Identification: Based on ridge characteristics (minutiae/Galton details) - e.g., ridge endings, bifurcations, islands.

    • Modern forensic practice emphasizes holistic assessment of all ridge details including minutiae, pores, and edge features rather than fixed numerical thresholds. BSA 2023 provisions support expert testimony based on comprehensive uniqueness evaluation.
  • ⭐ > Poroscopy (Edmond Locard): Study of sweat pores (their number, shape, size, position) on papillary ridges for identification. Pores are unique and permanent.

Dental & DNA ID - Teeth & Genetic Telltales

  • Dental Identification (Forensic Odontology):

    • Unique traits: Restorations, extractions, wear, anomalies.
    • Durability: Resists decay, highly fire-resistant (integrity varies with exposure duration), trauma.
    • Comparison: AM vs. PM dental records (X-rays, charts).
    • Age estimation: Gustafson's (adults), Demirjian's (children).
    • Bite marks: Injury pattern to dentition match (scientifically unreliable, largely rejected).
  • DNA Identification (Genetic Fingerprinting):

    • Definitive ID; unique profile (exc. identical twins).
    • Sources: Nucleated cells - blood, semen, saliva, hair root, bone, tooth pulp.
    • Techniques:
      • STR (Short Tandem Repeats): PCR-based, gold standard. 20 CODIS core loci.
      • mtDNA (Mitochondrial): Degraded samples, hair shafts. Maternally inherited.
      • Y-STR: Paternal lineage. Useful in sexual assaults.

    ⭐ Tooth pulp: Prime DNA source, protected by enamel/dentin, viable even after fire (>500°C) or decomposition.

Other Markers & Superimposition - Scars, Skulls & Signs

  • Scars:
    • Permanent; record of past injury/surgery.
    • Types: Linear, Stellate, Contracted, Keloid, Atrophic.
    • Age estimation: Fresh (red/blue) → Old (white, glistening).
    • Tattoo marks: Design, pigment, location aid identification.
  • Occupational Marks:
    • Specific to profession (e.g., tailor's callosity on finger).
  • Superimposition Techniques:
    • Skull-photo superimposition: Matches antemortem photo with recovered skull. 3D CT reconstruction of skull with bullet fragments
    • Key landmarks: Nasion, glabella, orbital rims, dental arcade.
    • Forensic imaging (CT, MRI, 3D reconstruction) provides dynamic, accurate identification methods for sex estimation and skull analysis.
  • Other Identifying Features:
    • Moles, nevi, birthmarks, deformities.
    • Gait, speech patterns (if known).

⭐ Gustafson's method (dental age): 6 criteria (attrition, 2ndary dentine, cementum, root resorption, transparency, periodontal recession).

High‑Yield Points - ⚡ Biggest Takeaways

  • Dactylography (fingerprints): highly reliable but complemented by DNA analysis; ridge patterns & minutiae are key.
  • Cheiloscopy (lip prints) & Palatal Rugoscopy: unique, valuable if fingerprints are absent.
  • Forensic Odontology: dental records, age estimation (Gustafson's, Demirjian's), bite marks.
  • DNA fingerprinting: conclusive identification using STRs (VNTRs largely historical).
  • Age estimation: ossification centers, dental development, epiphyseal fusion, pubic symphysis, advanced imaging.
  • Sex determination: from pelvis (sciatic notch, subpubic angle) & skull (mastoid process), DNA analysis definitive.
  • Craniofacial superimposition: matches skull with antemortem photographs for identification.

Practice Questions: Personal Identification Methods

Test your understanding with these related questions

Which of the following statements best describes a key characteristic of fingerprint development?

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Flashcards: Personal Identification Methods

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_____ is an exclusory test, which consists of orienting the (live) photographs in the exact same position as the dead body to know the identity of the person

TAP TO REVEAL ANSWER

_____ is an exclusory test, which consists of orienting the (live) photographs in the exact same position as the dead body to know the identity of the person

Photosuperimposition

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