Fingerprint Analysis

1. Context and Background

Fingerprint analysis is a forensic science discipline that involves the development, recognition, documentation, preservation, collection, and analysis of fingerprint evidence. It is crucial in criminal investigations for identifying individuals.

Murdoch University emphasizes respect for the Whadjuk and Binjareb Noongar people, acknowledging their enduring culture and the land's long-standing tradition as a place of learning.

2. Student Backgrounds and Course Relevance

Students may come from diverse backgrounds such as biology, chemistry, or law enforcement, and may work in laboratory or field settings. The course is designed to bridge these backgrounds with practical forensic applications.

3. Unit Aims and Objectives

• Equip students with scene-based skills for fingerprint evidence handling.
• Teach chemical, physical, and visual enhancement techniques relevant to crime investigations.
• Train students in database searches and fingerprint pattern matching.
• Apply the scientific method rigorously in fingerprint analysis.

4. Course Structure and Learning Approach

• Lectures and tutorials are aligned with practical laboratory exercises to simulate real-world fingerprint detection and analysis protocols.
• Training is practitioner-led, ensuring practical relevance.
• Students work in groups and must use lab coats, safety glasses, and lab notebooks.
• Lecture materials and readings are provided online before sessions.
• Each theoretical session is followed by a laboratory practical to reinforce concepts.

> Fingerprint analysis integrates scientific principles with practical forensic techniques to support criminal investigations through reliable evidence handling and interpretation.

1. Impression Evidence and Criminalistics Fundamentals

a) Unit Aims and Objectives

• Stay current with weekly readings to reinforce lecture and lab concepts.
• Practical laboratory attendance is mandatory; missed labs cannot be made up without valid medical certificates.
• Focus on assessments as outlined in the Unit Guide and Lab Manual, accessible via LMS.
• Laboratory reports form a key part of assessment.

b) Forensic Context and Purpose

• Impression evidence links the suspect, victim, or person of interest (POI) to the:
  • Crime scene
  • Weapon
  • Supporting or disproving witness testimony
  • Providing investigative leads (forensic intelligence)
• Minimum requirement: identification of evidence; comparison if circumstances allow.

c) Forensic Science Framework in Australia

• SWGFAST: Scientific Working Group on Friction Ridge Analysis, Study and Technology.
• Established standards by SWGFAST and the NIST OSAC Friction Ridge Subcommittee (2014).
• Key resources:
  • SWGFAST Standards: nist.gov/friction-ridge-subcommittee
  • Complete Latent Print Examination: clpex.com

d) Scientific Working Groups

• Provide standardized protocols and best practices for forensic analysis, especially friction ridge (fingerprint) examination.

e) Impression Evidence Overview

• Criminalistics: Application of scientific methods to legal matters (criminal and civil).
• Focus on comparative forensic sciences: comparing recovered evidence with control samples.
• Based on Locard’s Exchange Principle: every contact leaves a trace; evidence is exchanged between people and/or objects upon contact.

f) Criminalistics Stages in Evidence Analysis

• Recognition: Identifying potential evidence at the scene.
• Collection: Properly gathering and preserving evidence.
• Analysis: Scientific examination and comparison.
• Interpretation: Drawing conclusions based on analysis.
• Reporting: Documenting findings clearly for legal proceedings.

Key point: Impression evidence analysis relies on the scientific method and standardized protocols to link individuals and objects to crime scenes, supporting justice through reliable forensic intelligence.

1. Evidence Collection and Contamination Control

a) Key Concepts in Evidence Handling

• Identification: Recognizing evidence relevant to the investigation.
• Classification (and comparison): Grouping evidence by shared characteristics and comparing samples.
• Individualisation: Establishing unique features linking evidence to a specific source.
• Reconstruction: Using evidence to recreate the sequence or circumstances of a crime.

b) Impression Evidence

• Occurs when one object physically contacts another, transferring physical characteristics.
• Soft recipient material: Produces a 3D impression of the donor object.
• Hard recipient material with donor surface material (dirt, blood, ink): produces a 2D impression.
• Common types: fingerprints, tyre marks, footwear impressions, ballistic impressions, toolmarks.

c) Characteristics of Impression Evidence

• Identification vs. Individualisation: Identification groups evidence by class; individualisation links evidence uniquely to a source.

d) Role of Physical Evidence

• Establishes corpus delicti: essential facts proving a crime occurred and identifying the perpetrator.
  • Example: Blood, weapon, torn clothing in assault.
• Reveals modus operandi: the criminal’s characteristic method of committing a crime.
  • Example: Type of accelerant and fire-setting method in arson.
• Can indicate the signature of the criminal, aiding profiling.

e) Linking Evidence

• Connects Suspect, Victim, or Person of Interest (POI) to:
  • Crime scene
  • Weapon
  • Other individuals
• Supports or disproves witness testimony.
• Provides investigative leads and forensic intelligence.

f) Importance of Fingerprints in Forensics

• Fingerprints, alongside DNA, are among the most significant forensic evidence types.
• Extensive training and research focus on enhancing their evidential value.
• Evidence transfer involves class and ideally individual characteristics from finger to substrate.
• Types of fingerprints:
  • Latent: Invisible prints, requiring enhancement.
  • Patent: Visible prints (e.g., blood, ink).
  • Plastic: Impressions in soft materials.

g) Evidential Value

• Defined as the importance of evidence relative to the investigation.
• Evidence can support or refute an individual's involvement.
• Some evidence types provide more conclusive information than others.
• The order of evidence collection and analysis affects its value and interpretation.

> Evidential value determines how strongly evidence can link a suspect to a crime or exclude them.

1. Early Developments in Fingerprint Identification

• 1850s–1880s: Foundations laid by pioneers recognizing fingerprints as unique and permanent.
• Sir William Herschel (India, 1850s): Used fingerprints on contracts; documented his own prints over time to prove permanence.
• Henry Faulds (UK, 1860s–1880s): Observed fingerprint patterns on ancient pottery in Japan; proposed fingerprints as a means to identify individuals, including criminals.
• Published key works: Fingerprints as identifying marks (Nature, 1880), On the Skin-Furrows of the Hand, and On the Identification of Habitual Criminals.

2. Bertillon System and Biometrics

• Alphonse Bertillon (France, 1870s): Developed the Bertillon system, an anthropometric method for criminal identification.
• System included:
  • Precise body measurements.
  • Full-face and profile photographs ("mugshots").
• Although innovative, the system was eventually supplanted by fingerprint identification due to fingerprints' uniqueness and permanence.

3. Summary Table: Key Historical Figures and Contributions

Key point: Fingerprints are unique, permanent, and can reliably identify individuals, which led to their adoption over anthropometric methods like the Bertillon system.

1. Friction Ridges and Fingerprint Formation

Friction ridges are the raised portions of skin found on fingers, palms, and soles, characterized by ridges separated by furrows. Unlike most human skin, which is smooth and covered with hair follicles and oil glands, friction ridge skin lacks hair and oil glands but contains sweat glands (eccrine glands) that open at sweat pores on the ridges.

These ridges serve two main functions:

• Increase grip by enhancing friction between the skin and objects.
• Enhance tactile sensitivity by increasing the sense of touch.

2. Key Concepts in Fingerprint Science

• Dactyloscopy: The scientific study and comparison of friction ridges for identification purposes.
• Ridgeology: The analysis of ridge characteristics to compare and classify fingerprints.

3. Formation and Structure

• Ridges form due to the dermal papillae, which are projections in the dermis layer of the skin.
• Sweat glands develop in the dermis and open at the surface through pores located on the ridges.
• Perspiration is discharged through these pores and deposited onto the skin surface, contributing to fingerprint residue.

4. Historical and Scientific Foundations

• Galton’s principle: Friction ridges retain their unique patterns unchanged throughout life, making them a reliable biometric feature.
• Henry System: A classification method using fingerprint characteristics combined with digit identification, enabling systematic cataloging and retrieval.

5. Common Fingerprint Patterns

• Arch
• Loop
• Whorl

These patterns form the basis for fingerprint classification systems.

To retain: Friction ridges are unique, permanent skin features on fingers and palms, formed by dermal papillae and sweat glands, essential for fingerprint identification through dactyloscopy and ridgeology.

1. Skin and Fingerprints

• Ridge detail forms unique patterns on the skin surface, established by about 10 weeks of gestation and unchanged throughout life.
• Variations within friction ridge patterns include:
  • Minutiae: small details caused by environmental stresses and growth.
  • Pores: evenly spaced along ridges, responsible for sweat secretion.
• Fingerprint patterns are permanent, except altered by accidents, mutilation, or severe skin disease, as they originate in deep dermis layers.

2. Fingerprint Composition

• Fingerprints result from transfer of materials from finger to substrate:
  • Sweat secretions create latent marks; eccrine glands produce sweat unconsciously.
  • Sweat production increases with stress, emotion, or heat, aiding criminal investigations.
  • Sebaceous glands secrete sebum (oil) to protect and lubricate skin; abundant on face and scalp.
  • Sebaceous secretions often contaminate latent prints.
• Other contaminants (e.g., explosives, illicit drugs) may be present, providing intelligence information.

3. Fingerprint Types

4. Fingerprint Formation Factors

• Transfer depends on:
  • Surface temperature: sebaceous material adheres better to cooler surfaces than body temperature.
  • Surface structure: roughness and porosity affect deposition quality.

Fingerprint patterns are unique, permanent, and formed by sweat, skin cells, and oils transferred onto surfaces, with types classified as latent, patent, or plastic based on visibility and substrate interaction.

1. Fingerprint Formation and Surface Types

• Fingerprint formation depends on surface phenomena and the interaction between the finger and the surface.
• Surfaces are classified into three types for fingerprint deposition:
  • Porous: paper, cardboard, untreated wood
  • Non-porous: plastic, glass, metal, glossy paint
  • Semi-porous: glossy paper, wax paper, matt paint, wallpaper
• The surface properties must be considered before attempting latent print development.

2. Factors Affecting Fingerprint Visualization

Several factors influence the quality and detectability of fingerprints:

3. Selection of Visualization Techniques

• The choice of detection techniques depends on:
  • Surface nature: porous, non-porous, rough, or smooth
  • Contaminants present: e.g., blood or other substances
  • Environmental factors: wetness, temperature, humidity
  • Age of the fingerprint: older prints may require different methods
• Techniques are broadly categorized as:
  • Optical: visual enhancement using light sources or powders
  • Physical: powder dusting, lifting methods
  • Chemical: reagents reacting with fingerprint residues

4. Fingerprint Individualisation (Identification)

• Defined by the Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST) as the process of concluding two friction ridge impressions originate from the same source.
• Individualisation means the likelihood of another source producing the same print is so remote it is considered practically impossible.
• Important: Individualisation does not imply absolute exclusion of all other humans, but a practical certainty based on discriminating features.

To retain: Individualisation is a decision based on sufficient matching friction ridge features, not an absolute exclusion of all other possible sources.

1. Fingerprint Comparison and Individualization

Fingerprint analysis relies on ridge details, minutiae, and microscopic features for efficient examination and classification. Crucially, no two fingers have ever been found to possess identical ridge characteristics, and a fingerprint remains unchanged throughout a person's lifetime. These features enable reliable comparison and individualization.

2. Levels of Fingerprint Detail

3. First Level Detail

• Defines the fingerprint class based on ridge flow patterns.
• Common classes: Loop, Arch, Whorl.
• Useful for broad classification but insufficient for individualization.

4. Second Level Detail

• Focuses on minutiae, the small ridge discontinuities.
• Minutiae types and their location, direction, and spatial relationships provide the basis for individualization.
• Enables comparison between unknown prints and known samples.

5. Third Level Detail

• Examines individual ridge features such as:
  • Ridge width and shape
  • Distribution and size of pores
  • Minute imperfections (scars, cuts)
  • Morphological edges and textures
• Provides additional confirmation in fingerprint comparison.

6. Fingerprint Comparison Process

• Aim: Identify the source of fingerprints found at crime scenes.
• Comparison is typically between latent prints from a crime scene and known prints from suspects or databases.
• Utilizes all three levels of detail for thorough analysis.

7. Automated Fingerprint Identification System (AFIS)

• Example: Australian National AFIS, operational since April 31, 2001.
• Contains tenprint records from all arrested persons since 1941, police applicants, and other relevant occupations.
• Accessible from 39 metropolitan and remote locations across Australia.
• Supports uploading and searching of both tenprint and latent fingerprint data.
• Enables local review of AFIS search results.

To retain: Fingerprint individualization is based on the uniqueness of minutiae (second level detail) and is supported by first and third level details for classification and confirmation.