FLTCC Forensic Science Ridgeology A Closer Look at Fingerprints FLTCC Forensic Science

Fundamental Principles of Fingerprints A fingerprint is an individual characteristic. A fingerprint will remain unchanged during an individual’s lifetime. Fingerprints have general characteristic ridge patterns that permit them to be systematically classified. Kendall/Hunt Publishing Company

Ridgeology: The study of the uniqueness of friction ridge structures and their use for personal identification.1  As we have learned in our first lesson, a fingerprint is made of a series of ridges and valleys on the surface of the finger. The uniqueness of a fingerprint can be determined by the pattern of ridges and valleys as well as the minutiae points, which are points where the ridge structure changes. The koala is one of the few mammals (other than primates) that has fingerprints. In fact, koala fingerprints are remarkably similar to human fingerprints; even with an electron microscope, it can be quite difficult to distinguish between the two. Did you know? 1Introduction to Basic Ridgeology by David Ashbaugh, May 1999 Image from http://www.cs.usyd.edu.au/~irena/minutia.gif

What are fingerprints? Friction ridge skin pattern Found on fingers, palms, toes, soles of feet. Composed of ridges (hills) and furrows (valleys) Black = Ridges White = Valleys

Categorized by pattern and minutiae Fingerprints How are fingerprints analyzed? Categorized by pattern and minutiae

How are fingerprints analyzed? Patterns Arch Loop Whorl

There are 3 types of fingerprints Visible – left by dirt, grease, blood, etc. Does not need processing

There are 3 types of fingerprints Impression – indentation in soft material (butter, putty, tar, etc.) Does not need processing

There are 3 types of fingerprints Latent – requires processing to make visible and suitable for analysis

Fingerprint Recognition Fingerprint recognition is one of the oldest and most researched fields of biometrics. Some biological principles (Moenssens 1971) related to fingerprint recognition are as follows: Individual epidermal ridges and furrows have different characteristics for different fingerprints. This forms the foundation of fingerprint recognition The configuration types are individually variable; but they vary within limits that allow for a systematic classification. Herein lies the basis for fingerprint classification. The configuration and minute details of furrows are permanent and unchanging.

Fingerprint Formation Fingerprints are fully formed at about seven months of fetus development and finger ridge configurations do not change throughout the life of an individual except due to accidents such as bruises and cuts on the fingertips (Babler, 1991). Unrelated persons of the same race have very little generic similarity in their fingerprints. Parent and child have some generic similarity as they share half the genes. Siblings have more similarity. The maximum generic similarity is observed in monozygotic (identical) twins.

Fingerprint Classification Whorl Right Loop Left Loop Tented Arch Arch Classification of Fingerprints Large volumes of fingerprints are being collected in everyday applications-for e.g.. The FBI database has 70 million of them. To reduce the search time and computational complexity classification is necessary. This allows matching of fingerprints to only a subset of those in the database. An input fingerprint is first matched at a coarse level to one of the pre-specified types and then, at a finer level, it is compared to the subset of the database containing that type of fingerprints only. Numerous algorithms have been developed in this direction.

How are fingerprints analyzed? Minutiae Bifurcation Ridge Ending Dot Island

Line Types Classification Bifurcation: It is the intersection of two or more line-types which converge or diverge. Arch: They are found in most patterns, fingerprints made up primarily of them are called “Arch Prints”. Loop: A recursive line-type that enters and leaves from the same side of the fingerprint. Island: A line-type that stands alone.( i.e. does not touch another line-type) Ellipse: A circular or oval shaped line-type which is generally found in the center of the fingerprint, it is generally found in the Whorl print pattern. Tented Arch: It quickly rises and falls at a steep angle. They are associated with “Tented Arch Prints”. Spiral: They spiral out from the center and are generally associated with “Whorl Prints”. Rod: It generally forms a straight line. It has little or no recurve feature. They are gennerally found in the center. Sweat Gland: The moisture and oils they produce actually allow the fingerprint to be electronically imaged.

Feature Extraction Why are the classes not frequently used in biometric authentication? What is used for biometric classification? The human fingerprint is comprised of various types of ridge patterns. Traditionally classified according to the decades-old Henry system: left loop, right loop, arch, whorl, and tented arch. Loops make up nearly 2/3 of all fingerprints, whorls are nearly 1/3, and perhaps 5-10% are arches. These classifications are relevant in many large-scale forensic applications, but are rarely used in biometric authentication.

Computer software compares the location of these minutiae. Fingerprints Computer software compares the location of these minutiae.

Modern Fingerprint Analysis Fingerprints Modern Fingerprint Analysis Computer system stores patterns and minutiae of prints AFIS: automated fingerprint identification system

Automated Fingerprint Identification System (AFIS) When minutiae on two different prints match, these are called points of similarity or points of identification. At this point there is no international standard for the number of points of identification required for a match between two fingerprints. However, the United Kingdom requires a minimum sixteen points while Australia requires twelve. Automated Fingerprint Identification System (AFIS) http://www.fdle.state.fl.us/CrimeLab/images/fingerrint%20comparison%20for%20afis.jpg AFIS is a computerized system capable of reading, classifying, matching, and storing fingerprints for criminal justice agencies. Quality latent fingerprints are entered into the AFIS for a search for possible matches against the state maintained databases for fingerprint records to help establish the identity of unknown deceased persons or suspects in a criminal case.

Ridge Characteristics Use these characteristics as points of identification when comparing fingerprint samples. The more points you can find in common, the better the match!

Kendall/Hunt Publishing Company Fingerprint Minutiae Kendall/Hunt Publishing Company

Ridge Characteristics Minutiae—characteristics of ridge patterns Ridge ending Short ridge Dot or fragment Bifurcation Double bifurcation Trifurcation Bridge Island Enclosure Spur Kendall/Hunt Publishing Company

Ridge Characteristics Crossover Core Bifurcation (fork) Ridge ending Island Delta Pore Scar EXAMPLE http://cnx.org/content/m12574/latest/properties.jpg

How many ridge characteristics can you identify in this fingerprint? http://www.dkfz.de/tbi/projects/bmcv/images/iu_it246_04s_fingerprint1.jpg