Chapter 19: Friction Ridge System

Friction ridges

Friction ridges

_________ appear on the palms, soles, and ends of the fingers and toes.

Primary Friction Ridges

develop deep in the dermal layer of the skin. At about 14 weeks of gestation, sweat glands and sweat ducts begin to form.

Secondary Friction Ridges

Ridges that develop from week 17 and mature by week 24.

utero

Friction ridges develop in _____ and remain the same throughout life, barring some sort of scarring or trauma to the epidermal dermal margin of a friction ridge area.

Friction ridge print

a representation of a friction ridge pattern in some medium. It can be classified as either patent, if they are visible with the unaided eye, or latent if they require some sort of assistance to make them visible.

Patent Prints

an appear because of some transferable material on the ridge pattern or because the ridge pattern was transferred to a soft substrate that had “memory” and retained the impression.

Latent Prints

Composed of the sweat and oils of the body that is transferred from the ridge pattern to some substrate.

Fingerprint powder

Most familiar visualizing technique; is colored, fluorescent, or magnetic materials that are very finely ground, which is brushed lightly over a suspected print to produce contrast between the background and the now visible print.

Amino Black

Protein dye is sensitive to blood, turning a blue-black color in its presence. Treatment with a physical developer may be done after amido black to improve the developed print.

Aqueous amido black

The protein dye solution is sensitive to blood, turning a blue-black color in its presence. Treatment with a physical developer may be done after amido black to improve the developed print. Can be washed over any nonporous surface; the item may also be submerged in the solution.

Aqueous leucocrystal violet

Enhances and develops latent prints stained with blood on porous or nonporous surfaces. Best applied by washing or submersion.

Gentian crystal violet

A protein-dye that stains the fatty portions of sebaceous sweat a deep purple color; it also works on bloody prints. GCV will visualize latent prints on the adhesive side of all tapes. Fluoresces at 525, 530, and 570nm (use red goggles); also at 485 and 450nm (use orange goggles).

DFO

A ninhydrin analog that reacts to the amino acids present in body proteins; is especially good for paper evidence. O

Glue fuming

Fumes from cyanoacrylate ester adhesives (Super Glue® and similar products) will develop latent prints by binding the proteins in the prints.

Ninhydrin

Develops latent prints on porous surfaces like paper by reacting with amino acids in latent print residue. In a fume hood, the specimens are submerged in the ninhydrin solution and then air-dried.

Physical developer

A silver-based liquid reagent that reacts to lipids, fats, oils, and waxes present in the print residue. It is good for porous objects but should be the last process in the chemical sequence.

Small particle reagent

A physical development technique in which small black particles adhere to the fatty substances left in print residue and is useful on many different surfaces. Well known for its ability to develop prints on wet surfaces and even under water.

Sudan black

Working best on glass, metal, or plastic materials that are greasy or sticky, it is is a dye that stains the fatty components of sebaceous secretions.

Vacuum metal deposition

This is reported to be the most effective technique for most smooth, nonporous surfaces. The process evaporates gold or zinc in a vacuum chamber that coats the specimen surface with a microscopic layer of metal.

Loops

have one or more ridges entering from one side of the print, curving back on themselves, and exiting the fingertip on the same side.

Ulnar Loop

the loop enters and exits on the side of the finger toward the little finger.

Radial Loop

the loop enters and exits on the side toward the thumb

Type Lines

two diverging ridges that surround the loops

Delta

point of divergence

Core

central portion of the loop

Automated Fingerprint Identification Systems (AFIS)

computerized databases of digitized fingerprints that are searchable through software—essentially, a computer and a scanner hooked to a network-type server computer.

Integrated Automated Fingerprint Identification Systems (IAFIS)

• It can digitally capture latent print and 10-print images and then:

  • enhance an image to improve its quality;

  • compare crime scene fingerprints against known 10-print records retrieved from the database;

  • search crime scene fingerprints against known fingerprints when no suspects have been developed; and

  • automatically search the prints of an arrestee against a database of unsolved cases.

The Universal Latent Workstation

the first in a new generation of interoperable fingerprint workstations.

Level 1 detail

includes the general ridge flow and pattern configuration. It is not sufficient for individualization but can exclude an individual.

Level 2 detail

includes formations, defined as ridge endings, bifurcations, dots, or combinations of these features.

Level 3 detail

includes all attributes of a ridge, such as a ridge path deviation, width, shape, pores, edge contour, incipient ridges, breaks, creases, scars, and other permanent minutiae.

Henry’s original design

The modern system of fingerprint classification is based on _______, which could process a maximum of 100,000 sets of prints, with modifications by the FBI to allow for the huge number of entries that have accumulated over the years.