Fingerprint Analysis

1883: Alphonse Bertillon (France)

1st systematic attempt at personal identification / anthropometry - body height, length of middle finger, length of left foot, length of outstretched reach of both arms, width of head, length of head

1892: Sir Francis Galton (England)

published textbook Finger Prints / outlined a fingerprint identification system / suggested methods for recording fingerprints / assigned three pattern types / demonstrated two fundamental principles underlying fingerprint identification system

Fundamental principles

uniqueness and persistent

Uniqueness

Galton calculated that there was a possible existence of 64 billion different fingerprints / no 2 fingerprints have yet been found that are identical / even identical twins have different fingerprints

Persistent

a fingerprint remains unchanged during an individual’s lifetime, except for environmental changes (scars)

1897: Sir Edward Richard Henry

developed a searchable filing system / adopted by Scotland Yard

1911: People v. Jennings

Thomas Jennings murdered and robbed Clarence Hiller / 1st official case to integrate fingerprints as plausible evidence in U.S.

What are fingerprints

friction skin ridges found on the palm side of the fingers and thumbs (also found on palms, toes, and soles of feet) / designed for firmer grasp and to prevent slippage / do not contain hair follicles

Development of fingerprints: 10th week of gestation

fingers are developing

Development of fingerprints: 12th to 16th week of gestation

skin of fetus transforms from thin transparency to waxy coating, basal layer begins to outgrow inner dermis and epidermis skin layers

Factors that impact fingerprints

position in womb, composition and density of amniotic fluid, genetics, etc.

Scars

can change fingerprints but becomes a new identifying part of the print / must cut deeper than dermal papillae of dermis

Attempts to remove fingerprints: John Dilinger (1934)

cut fingers and poured acid into them

Attempts to remove fingerprints: Roscoe Pitts (1941)

replaced finger skin with skin from chest

Attempts to remove fingerprints: Mark George (2007)

replaced finger skin with skin from bottom of his feet

Ridge fingerprint pattern types

loops (60-65%), whorls (30-35%), arches (5%)

Loops

must have one delta / triradius surrounded by type lines and a core

Type lines

ridges that split around the delta

Specific classification of loops

one or more ridges enter from one side of the print, recurve, and exits from the same side

Ulnar loop (known print)

opens toward the little finger

Radial loop (known print)

opens toward the thumb

Right slant loop (unknown print)

ridges come in from right side, travel upwards and left and then recurve and exit on right side

Left slant (unknown print)

ridges come in from left side, travel upwards and right and then recurve and exit on left side

Whorls

ridges are generally circular / all whorl patterns have type lines and at least two deltas

Plain whorl

at least 1 ridge makes a complete circuit / imaginary line between deltas touches spiral ridge

Central pocket loop whorl

at least 1 ridge makes a complete circuit / imaginary line between deltas does not touch spiral ridge

Double loop whorl

made of 2 loops combined together

Accidental whorl

contains 2 or more patters or doesn’t fit anywhere else

Arches

ridge enters from one side of the print, rises in the center and exits on the other / do not have type lines, deltas, or cores

Plain arch

ridges rise in the center in a wave-like pattern

Tented arch

ridges rise in the center with a sharp spike

Minutiae

details in a fingerprint

Galton features

minutiae / identify, number, and location imparts individuality to a fingerprint / used to make a point by point comparison by expert fingerprint examiners / 8-16 points considered sufficient for comparison

Core

center area of fingerprint

Ridge ending

a ridge that ends abruptly

Short ridge

a ridge that commences, travels a short distance, then ends

Bifurcation/Fork

a single ridge that divides into two

Delta

point at the divergence of 2 type lines (triangle)

Hook

a bifurcation with a short ridge branching off a longer ridge

Eye

a bifurcation that reunites

Dot/Island

a ridge with equal length and width

Crossover/Bridge

a short ridge that runs between two parallel ridges

Enclosure

a bifurcation that reunites around a short ridge or dot

Types of crime scene prints

visible, plastic, etched, latent

Visible prints

made by fingers coated in a colored material such as blood, paint, grease, or ink touching a surface

Plastic prints

made when a finger leaves an impression in a soft material such as putty, wax, or dust

Etched prints

made when fingerprint on metal has been exposed to high heat

Latent prints

made by the sweat released from pores on friction ridges on fingers / invisible to the naked eye / prints need to be developed in order to be visualized

Methods of detecting fingerprints

physical: apply fine particles to residue where it preferentially adheres / chemical: apply chemicals that adhere to print residue / special illumination: use different wavelengths of light to visualize

Physical methods

adheres to perspiration residues and body oil deposits of ridges / applied with camel hair, fiberglass or magnetic brush / select color powder with best contrast: regular powders (black or light grey), magnetic sensitive powders, luminescent powders, small particle reagent

Chemical methods: cyanoacrylate fuming

heat superglue, cyanoacrylate ester fumes react with fats; used on nonporous surfaces, permanent

Chemical methods: iodine fuming

sublimate solid iodine, vapors react with fats, not permanent, fumes are toxic

Chemical methods: physical developer

silver nitrate reacts with NaCl to form gray AgCl, useful on items once wet, destroys proteins

Chemical methods: ninhydrin

spray print, reacts with amino acids, very sensitive, used on porous surfaces, permanent / DFO is an analog, can use before ninhydrin to enhance print

Illumination: reflected ultraviolet imaging system (RUVIS)

useful but can damage skin, eyes, and DNA in fingerprint

Illumination: ALS

525 nm / bright white lights with color filters

Illumination: laser

monochromatic

Document examination

be careful of solvent based reagents (ninhydrin) that may cause ink to run

DNA profiling

in blood, avoid short save UV light / other fingerprints, avoid physical developer and magnetic powder / always swab for DNA first

Fingerprinting at the crime scene

photograph first, transport items back to the laboratory for processing if possible, treat remaining surfaces with suitable development technique, nonporous surfaces: powders, porous surfaces: ninhydrin

Automated fingerprint identification systems (AFIS)

prints are scanned and encoded by computers / digitally stores position and orientation of minutia for each print / produces a list of prints with the closest correlation to a question print for the examiner to compare / still manually search known suspects in each case / forward search and reverse search / known to known or unknown to unknown comparisons

Mayfield incident

2004 bombings in Madrid, Spain / FBI linked latent prints found to Brandon Mayfield / found prints actually match Daod, an Algerian national / led to more stringent analysis

ACEV

analysis, comparison, evaluation, verification

Analysis

determine suitability of print

Comparison

level 1: overall pattern and ridge flow / level 2: minutia - type and location / level 3: pore shape, locations, numbers, relationships, shape and size of edge features

Evaluation

insufficient ridge detail to make conclusion / exclusion / individualization

Verification

independent examiner verifies conclusions

International Association for Identification

advancement of identification techniques through education / disciplines include biometrics, BPA, crime scene, digital evidence, facial ID, footwear, tire track, art, photography, fingerprints / published Journal of Forensic Identification

OSAC Friction Ridge Subcommittee

standards and guidelines for analysis of friction ridges on hands and feet