The Science of Fingerprints

These flashcards provide key vocabulary and concepts relevant to the science of fingerprints, including historical developments, classification types, techniques for fingerprint recovery, and significant cases.

The Three Principles of Fingerprints

1. A fingerprint is an individual characteristic; no two fingers have yet been found to possess identical ridge characteristics. 2. A fingerprint remains unchanged during an individual's lifetime. 3. Fingerprints have general ridge patterns that permit them to be systematically classified.

Friction Ridge Skin

A layer of skin unique to the palmar surfaces of the hands and plantar surfaces of the feet, characterized by raised ridges and valleys that provide traction and grip.

Minutiae (Galton Details)

The unique ridge features of a fingerprint, including ridge endings, bifurcations, dots, islands, and enclosures. These provide the basis for individual identification.

Level 1 Detail

The general flow of the ridges and the overall pattern type, such as a loop, whorl, or arch. This level can exclude a suspect but cannot be used for individual identification.

Level 2 Detail

Specific ridge characteristics or minutiae, such as the exact locations of bifurcations and endings. This level is used for the individualization of a print.

Level 3 Detail

Microscopic details of the friction ridges, including the specific shape of the ridge edges and the position of sweat pores. This requires high-resolution imaging.

Patent Impressions

Visible fingerprints made when fingers contaminated with a visible substance like blood, ink, paint, or grease are pressed against a surface.

Latent Impressions

Fingerprints that are invisible or partially visible to the naked eye. They are formed by the transfer of body oils and perspiration to a surface and usually require development to see.

Plastic Impressions

Three-dimensional fingerprint indentations left in soft materials such as wax, soap, putty, or fresh paint.

Loops

The most common fingerprint pattern (60-{65}\%), where ridges enter from one side, recurve, and exit from the same side. Ulnar loops open toward the pinky, while Radial loops open toward the thumb.

Arches

The rarest pattern type (5\%) where ridges enter from one side and exit the other. Plain Arches have a gentle rise, while Tented Arches have a sharp, vertical spike in the center.

Whorls

Patterns found in 30-{35}\% of fingerprints that have at least one recurving ridge and two deltas. Subtypes include Plain Whorls, Central Pocket Loops, Double Loop Whorls, and Accidental Whorls.

ACE-V Methodology

The scientific four-step process for fingerprint examination: 1. Analysis of the unknown print. 2. Comparison with a known print. 3. Evaluation of similarities and differences. 4. Verification by a second examiner.

Henry Classification System

A historical system used to categorize fingerprint cards by assigning point values to whorls on specific fingers. The primary classification results in a fraction based on these values plus 1/1.

AFIS

Automated Fingerprint Identification System, a national digital database maintained by the FBI for storing and searching fingerprint and criminal history records.

RUVIS Technology

Reflective Ultraviolet Imaging System used to locate and visualize latent fingerprints on non-porous surfaces without the use of chemicals or powders by using ultraviolet light.

Cyanoacrylate (Super Glue) Fuming

A chemical technique for non-porous surfaces where glue vapors react with perspiration and oils to form a hard, white polymer on the ridge patterns.

Ninhydrin

A chemical reagent used on porous surfaces like paper. It reacts with amino acids in sweat to produce a purple-blue color known as Ruhemann's Purple.

Iodine Fuming

A process involving the sublimation of iodine crystals. The vapors react with fatty oils to make a temporary yellow-brown print that must be photographed immediately.

DFO (1,8-Diazafluoren-9-one)

A chemical used on porous surfaces that is more sensitive than Ninhydrin. It reacts with amino acids and fluoresces under high-intensity light sources.

Physical Developer (PD)

A silver-nitrate-based reagent used to develop prints on porous surfaces that have been wet or damp, where other chemical methods might fail.

Vacuum Metal Deposition (VMD)

An extremely sensitive development method that uses the deposition of thin layers of gold and zinc in a vacuum chamber to reveal prints on smooth, non-porous surfaces.

Anthropometry (Bertillonage)

A system developed by Alphonse Bertillon that used 11 body measurements for identification. It was replaced by fingerprinting after the Will West case proved it unreliable.

Sir Francis Galton

The researcher who published 'Finger Prints' in 1892, establishing the scientific basis for fingerprinting, including their permanence and uniqueness.

Brandon Mayfield Case

A landmark error in 2004 where the FBI mistakenly identified an American attorney's print as matching a partial latent print from the Madrid train bombings.

LiveScan

The electronic capturing of fingerprints using a specialized glass plate and sensor, eliminating the need for traditional ink and paper cards.