History & Composition of Fingerprints – Comprehensive Lecture Notes

Quick Review: Powdering & Lifting Fingerprints

  • Personal Protective Equipment (PPE)

    • Gloves are mandatory; masks recommended (powder can become airborne).
    • Operate inside a fume hood; no food or drink in the lab (Health & Safety compliance).

  • Powdering Basics

    • Definition: Applying finely-ground, coloured powder to a non-porous surface to make latent prints visible.
    • Powder adheres to moisture, oils, and other fingerprint residues.
    • Common brush types:
    • Fiberglass filament brush
    • Camel-hair brush
    • Feather duster

  • Application Technique

    • Deposit small amount of powder, then gently brush.
    • Move the brush with the direction of emerging ridges.
    • Stop when the print reaches optimal clarity—“over-powdering” obscures detail.

  • Marking Developed Prints

    • Circle print with wax pencil / dry-erase marker.
    • Label sequentially: R1, R2, …; add directional arrow if helpful.
    • Include date & initials.
    • Place scale near (not touching) the print after the first photographs.
    • Lightly powder the scale and writing to keep overall exposure consistent in photographs.

  • Photography Sequence

    • Overall shot → mid-range → close-up → close-up with scale (all on the same focal plane).

  • Lifting Procedure

    • Use hinge lifter or fingerprint tape.
    • Anchor the tape’s leading edge ahead of the print, apply even downward pressure, advance to cover the ridge detail.
    • Peel back smoothly, avoiding creases, and mount on a lift card.
    • Complete the lift card: case details, sketch of print location.

Historical Milestones in Fingerprints

  • Ancient & Medieval

    • 300 B.C.300\,\text{B.C.} China: fingerprints as proof of identity.
    • 702 A.D.702\,\text{A.D.} Japan: documented use.
    • Qin Dynasty (≈221–206 B.C.221\text{–}206\,\text{B.C.}): handprints used in burglary cases.

  • 17th–18th Centuries

    • Dr. Nehemiah Grew (1684): first European microscopic description of friction-ridge skin.
    • Marcello Malpighi (1687): ridges increase skin–object friction.
    • Dr. J. C. A. Mayer (1788): first to declare ridge patterns unique.

  • 19th Century

    • Dr. Jan Purkinje (1823): classified fingerprints into nine pattern types—precursor to the Henry system.
    • Sir William Herschel (1858, India):
    • Right-hand print used as a contract signature (Rajyadhar Konai).
    • Demonstrated print persistence across 57 years (samples: 1859,1877,19161859,1877,1916).
    • Dr. Henry Faulds (1880): journal article advocating evidentiary value; urged police adoption.
    • Anthropometry (Alphonse Bertillon, 1882): body-measure identification—later supplanted by fingerprints.
    • Dr. Arthur Kollman (late 1800s): fetal ridge formation, identified volar pads (visible by 4ᵗʰ fetal month; complete by 6ᵗʰ).
    • Sir Francis Galton (1892):
    • Book “Finger Prints”; proved uniqueness & permanence.
    • Named minutiae (“Galton details”).
    • Promoted fingerprints over Bertillonage (1888).

  • Global Systems & First Cases

    • Juan Vucetich (1891, Argentina): devised own classification; enabled card filing/searching.
    • Rojas Murders, 1892 (Argentina): first homicide solved solely with fingerprint evidence; nation adopted fingerprint identification.
    • Henry Classification System (1897, India/England): created by Azizul Haque & Hem Chandra Bose; supervisor – Edward Henry.
    • Belper Committee (1900): England decides to classify all criminal records by fingerprints; Henry system becomes standard.

  • North American Adoption

    • 19021902 USA: New York State Civil Service Commission—first systematic government use.
    • Canada:
    • 19041904 Edward Foster (Dominion Police) exposed to Scotland Yard lecture; lobbied for adoption.
    • 19081908 Order-in-Council under Identification of Criminals Act legalizes prints; Bertillon system phased out by 19101910.
    • 19111911 National Fingerprint Bureau (RCMP) opens with 2,0422{,}042 sets; photography sanctioned the same year.
    • 19141914 First Canadian conviction via fingerprints (Petawawa, ON).
    • 19501950 OPP Identification Bureau formed.
    • Kejimkujik Petroglyphs (Nova Scotia): oldest N. American depiction of friction ridges & flexion creases (anthropological significance).

  • 20th-Century Scientific Advances

    • Wilder & Wentworth (1918): book integrates law enforcement & science; validates third-level detail (pores, ridge edges, scars).
    • Dr. Harold Cummins (1943): volar pad regression aligns with ridge development; pad size/position influences patterns.
    • Dr. Alfred Hale (1952): fetal cross-sections; detailed ridge formation & differential growth.
    • Salil Kumar Chatterjee (1962): “Edgeoscopy” – ridge edge shapes for identification.
    • Dr. M. Okajima (1976): studied incipient ridges (immature, thin ridges).

Structure & Function of Skin

  • General Skin Functions

    1. Container for skeletal structures & organs.
    2. Sensory input: temperature, texture, pain.
    3. Waste elimination & thermoregulation via sweating (salts, amino acids, ammonia, urea).

  • Friction Ridge Skin (Hands & Feet)

    • Ridges + pores enhance grip.
    • Flexion creases allow movement.

  • Quantitative Facts

    • Total body skin ≈ 1.5–2 m21.5\text{–}2\,\text{m}^2; only ≈0.08 m2\approx0.08\,\text{m}^2 is friction skin.
    • Thickness rarely > 2 mm2\,\text{mm}; thickest on palms/soles.

Skin Layers

  • Epidermis (outer barrier; continuous cell turnover)

    • Five strata (deep → superficial):
    1. Stratum Basale (generating layer; melanocytes produce melanin).
    2. Stratum Spinosum (flexibility, UV protection).
    3. Stratum Granulosum (waterproof barrier).
    4. Stratum Lucidum (stretch & cell degeneration).
    5. Stratum Corneum (dead cells; external “dust”).
    • Complete cell migration cycle ≈ 28 days28\,\text{days} (basale → corneum).

  • Dermis (supportive connective tissue)

    • Two sub-layers: papillary (outer) & reticular (inner).
    • Houses nerves, blood vessels, sebaceous & sweat glands.
    • Contributes to touch perception & temperature regulation.

Sweat Glands

  • Humans possess 1.6–5 million1.6\text{–}5\,\text{million} glands.

  • Density on palms/soles: 600–700 glands/cm2600\text{–}700\,\text{glands/cm}^2.

  • Types & Roles

    1. Eccrine (entire body; only appendage in friction skin)
    • Simple tubular; ducts exit at ridge pores.
    • Secrete ≈99%\approx99\% water + electrolytes for cooling.
    • Group-functioning; larger & more active on palms/soles.
    1. Apocrine (hairy regions; oily secretion; emotional stimuli—anxiety, fear).
    2. Apoeccrine (discovered 19871987; hybrid; watery secretion; develops at puberty).

  • Fingerprint Residue Composition

    • ≈99%\approx99\% water.
    • ≈1%\approx1\% organic & inorganic salts, amino acids, lipids.
    • Residue chemistry changes as water evaporates → necessity for multiple development techniques.
    • Probability of successful development ∝ 1time since deposition\tfrac{1}{\text{time since deposition}} (inverse relationship).

Biological Variability & Permanence

  • Injury & Healing

    • Damage limited to epidermis → identical ridge pattern after regrowth.
    • If the generating layer (Stratum Basale blueprint) is damaged, new pattern forms.
    • Dermal injuries produce scars—permanent, unique third-level detail.
    • Scar features vary with deposition pressure/movement; they appear as voids or distortions in impressions.

  • Wound-Healing Phases

    1. Inflammation
    2. Proliferation/Tissue Formation
    3. Remodeling

  • Creases vs. Scars

    • Creases may develop from environment, diet, age; presence varies among individuals.
    • Must not be misinterpreted as scars; note but do not base identification solely on creases.

  • Aging Effects

    1. Surface ridges flatten ⇒ less pronounced in impressions.
    2. Dermal elasticity loss ⇒ skin becomes flaccid & wrinkles form.
    • Wrinkles: dermal changes reduce stretchability & resilience.

  • Incipient Ridges

    • Undeveloped, narrow, “rudimentary” ridges.
    • Excluded from classification, yet can aid identification if present in both questioned & known prints.

Key Takeaways & Practical Implications

  • Fingerprint identification rests on three foundational principles:

    1. Uniqueness (no two prints identical; established by Mayer, Galton).
    2. Permanence (persistence over a lifetime; demonstrated by Herschel).
    3. Classifiability (Henry, Vucetich systems allow efficient filing & retrieval).

  • Modern science validates not only overall ridge flow (level 1) and minutiae (level 2) but also pores, edges, scars (level 3) as unique & permanent.

  • Successful latent print recovery depends on:

    • Timely scene processing (residue evaporation).
    • Proper powdering technique (avoid over-application).
    • Accurate documentation (photos, lift cards, sequential labeling).
    • Health & safety adherence in the lab.

  • Ethical/Legal Context:

    • Shift from Bertillon measurements to fingerprints reflected quest for more reliable, science-based identification.
    • Early cases (Rojas murders, Petawawa conviction) established forensic precedent for courtroom acceptance.

  • Research fronts continue (edgeoscopy, incipient ridge studies) to refine comparison criteria, bolstering both accuracy and admissibility.