Fingerprints: History and Development

Fingerprints: History

• The first systematic method for personal identification was developed by Alphonse Bertillon, a French police expert.
• Bertillon's method used detailed descriptions, full-length and profile photographs, and precise body measurements (anthropometry).
• In 1892, Francis Galton published his book "Finger Prints," advocating fingerprinting as a supplement to Bertillon's system.
• The British government adopted fingerprinting based on Galton's proposal.
• Classification systems were created to efficiently file and search the increasing number of fingerprints, allowing for logical organization.
• Dr. Juan Vucetich developed a classification system used in Spanish-speaking countries, while Sir Edward Henry created a comparable system for English-speaking countries.
• The Bertillon system failed to distinguish between Will West and William West in 1903, which highlighted the superiority of fingerprinting.
• The use of fingerprinting by the New York City Civil Service Commission in 1901, and training provided by Scotland Yard representatives at the 1904 World's Fair, propelled the widespread adoption of fingerprinting in major U.S. cities.

Fingerprint Principles

• Fingerprints are reproductions of friction skin ridges on the fingers and thumbs.
• Fingerprints are unique; no two fingers have identical ridge characteristics.
• Fingerprint patterns remain unchanged throughout an individual's life.
• Ridge patterns allow for systematic classification of fingerprints.

Principle One

• The probability of two identical fingerprint patterns in the global population is extremely low.
• Based on Galton's calculations, there are an estimated 64 billion different fingerprint patterns.
• Individuality in fingerprints is determined by the unique details (minutiae) rather than the overall shape or pattern. Key characteristics include bifurcations, ridge endings, ridge dots, and enclosures.
• A minimum of 150 minutiae are typically present on an average finger. No specific number is legally fixed for identifying a match in the U.S.
• Fingerprint analysis in court requires an expert to demonstrate a detailed point-by-point comparison between the questioned print and a known sample to establish identity.

Principle Two

• The outer layer of skin is the epidermis, while the inner layer is the dermis.
• Dermal papillae, the layer between the epidermis and dermis, control the form and pattern of skin ridges.
• Ridge patterns are established during fetal development and largely remain unchanged afterward, except for natural growth.
• Pores on each skin ridge lead to sweat glands. Perspiration and oils transferred to a surface create visible or latent impressions.

Principle Three

• Fingerprints are broadly classified into three main categories: loops, arches, and whorls.
• Approximately 60-65% of people have loop patterns, 30-35% have whorl patterns, and about 5% have arch patterns.

Loops

• Loops have one or more ridges entering from one side of the print, curving around, and exiting on the same side.
• Ulnar loops open toward the little finger, while radial loops open toward the thumb.
• Loops always have one delta.
• The pattern area of the loop is surrounded by type lines, and a core is found near the center.

Whorls

• Whorls are characterized into four categories: plain, central pocket loop, double loop, and accidental.
• Plain whorls and central pocket loops have at least one ridge that completely encircles the center.
• Two deltas are always present in whorl patterns. Double loops are formed by two distinct loops connecting. An accidental is a pattern that does not fit into the other categories.

Arches

• Arches are the least common fingerprint type. They are divided into plain and tented arches. Plain arches are formed by ridges entering from one side, rising, and exiting on the other. Tented arches have one or more sharp ridges or an upthrust in the center. Arch patterns lack type lines, deltas, and cores.

ACE-V

• A four-step process for fingerprint analysis: Analysis, Comparison, Identification, and Verification.
• Level 1: Analysis of general ridge flow and pattern configuration.
• Level 2: Locating and comparing ridge characteristics (minutiae)
• Level 3: Examining finer details of minutiae, including pores, breaks, creases, scars, or other permanent characteristics.

Primary Classification

• Fingerprint classification systems use characteristic patterns to assign a primary classification.
• The presence or absence of whorls determines the primary classification. 
• Whorls are given numerical values, while loops or arches are assigned a 0. Values from each fingerprint are summed to a fraction.

AFIS

• Automation Fingerprint Identification System (AFIS) is a crucial technology.
• AFIS functions by scanning and digitally encoding fingerprints, which enables high-speed computerized processing.
• AFIS aids in classifying and retrieving fingerprints by converting images into digital minutiae.
• When a search is complete, a list of potential matches is generated to be verified by a fingerprint expert.
• AFIS systems encompass local, regional, and global databases.

Latent Prints

• Latent prints are invisible to the naked eye, formed by perspiration and oils transferred to a surface.

Visible Prints

• Visible prints appear due to their contact with substances like blood, paint, grease, ink, or other colored materials.
• Plastic prints are formed by fingers pressing against a soft surface leaving a direct impression.

Detecting Prints on Non-Porous Surfaces

• Latent prints on hard surfaces are commonly developed with powders that adhere to perspiration and oils.
• Super Glue® (cyanoacrylate) fuming is used for a range of surfaces to visualize latent prints.
• Fluorescent dye combinations with alternative light sources (LAS) can also be helpful to visualize prints.

Detecting Prints on Porous Surfaces

• Porous surfaces (e.g., papers, cardboard) are examined by chemical methods like iodine fuming, ninhydrin, or Physical Developer.
• Iodine fuming produces temporary visualizations.
• Ninhydrin reacts with amino acids to produce a purple/blue color.
• Physical Developer is used on surfaces that may have been wet. If all three are required, iodine fuming is done first, then ninhydrin, and finally physical developer.

Preserving Prints

• If possible, small objects should be transported intact for preservation.
• Photographing prints before any other preservation method is critical.
• Broad adhesive tape is ideal for lifting latent prints from large surfaces. A contrasting card should accompany the lifted print.

Digital Imaging

• Digital imaging translates image from a finger print into a digital computer file.
• This enhances latent prints for a more comprehensive examination.
• Enhanced fingerprint images can be compared side to side.