Detecting, Identifying, and Evaluating Patent & Latent Prints FINGERPRINTS Detecting, Identifying, and Evaluating Patent & Latent Prints

History of Fingerprints 1880 – Scottish doctor Henry Fauld suggests the application of fingerprinting as a means of identification 1883 – Frenchman Alphonse Bertillon creates anthropometry as a means of identification 1891 – Argentinian Dr. Juan Vucetich develops a system of classifying fingerprints still used in Spanish speaking countries today 1892 – Englishman Francis Galton publishes Finger Prints, a text identifying the 3 main ridge patterns and demonstrating that one’s prints are permanent and unique. 1897 – Englishman Sir Edward Richard Henry developed a classification system used by English speaking countries 1903 – End of anthropometry – 2 prisoners found to have same measurements and are mistaken for each other.

History of Fingerprints 1904 First American police trained in fingerprint techniques by Scotland Yard; fingerprinting became widely used in all major US cities 1924 FBI fingerprint identification records created 1946 The F.B.I. processes 100 million fingerprint cards in manually maintained files; by 1971, 200 million cards.

Basic Traits of Fingerprints

Fingerprint Basics The pattern of friction ridges of the fingers, palms, toes, and sole of the foot are formed in utero by about 5 months. They are unique to the individual and remain unchanged over a lifetime. Even identical twins have different fingerprints. Fingerprint configurations are probably determined by multiple genes – possibly 64 billion different patterns On the top of the ridges are pores that allow sweat and oil to exit from glands. Fingerprints are left by the transfer of oil or amino acids to a surface, substances on the fingers like paint or blood, or by leaving a print in a soft substrate. Prints that can't be readily seen on a surface are called latent and must be visualized by various methods.

Characteristics of Fingerprints Arch: ridges enter from one side, rise to a ridge in the center and exit out the opposite side. (no deltas) Tented Arch: at least one arch rises to 45 degree angle or less. Whorl: At least one ridge makes a 360 degree circle in the center of the print. (2 deltas) Loop: One or more ridges make a loop and then exit the same side they entered. (1 delta)

Characteristic of Fingerprints Approximately five percent (5%) of all fingerprints are Arches, 30% are Whorls and 65% are Loops.                                  

Evaluating the Pattern The uniqueness of a fingerprint can be determined by the pattern of ridges and furrows as well as the minutiae points. Minutiae points are local ridge characteristics that occur at either a ridge bifurcation (split into two) or a ridge ending.

3 Fundamental Principles 1st – A fingerprint is an individual characteristic; no two fingerprints have yet been found to possess identical ridge characteristics 2nd – A fingerprint will remain unchanged during an individual’s lifetime 3rd – Fingerprints have general ridge patterns that permit them to be systematically classified

Minutiae patterns ridge ending - a ridge that ends abruptly; bifurcation - a single ridge that divides into two ridges; lake or enclosure - a single ridge that bifurcates and reunites shortly afterwards to continue as a single ridge; short ridge, island or independent ridge - a ridge that commences, travels a short distance and then ends; dot - an independent ridge with approximately equal length and width; crossover or bridge - a short ridge that runs between two parallel ridges.

Comparing Fingerprint Pattern Fingerprint matching techniques can be placed into two categories: Minutiae-based techniques first find minutiae points and then map their relative placement on the finger. It is difficult to extract the minutiae points accurately when the fingerprint is of low quality. The correlation-based method is able to overcome some of the difficulties of the minutiae-based approach. Correlation-based techniques require the precise location of a registration point and are affected by image translation and rotation.

AFIS Automated Fingerprint Identification Systems Uses digitized images of print minutiae (ridge endings and bifurcations) Can compare a set of 10 prints to 500,000 other sets in 8 tenths of a second. Final matching is done by a person.

IV: Run a Comparison III: Identify Specific Patterns on 2nd Print II: Identify Specific Patterns on 1st print I: Mark Print IV: Run a Comparison

Prior to AFIS, a single technician combing through LA’s 1 Prior to AFIS, a single technician combing through LA’s 1.7 million fingerprint cards would have taken approximately 67 YEARS to identify a match.

Latent Prints Latent prints are those that cannot be seen by the naked eye. They are caused by the perspiration and other materials that may be on the ridges of the skin. The method used for obtaining latent prints depends on the type of surface to be examined, the manner in which the prints were left, and the quantity of material taken to the crime lab. They are compared to the prints of all persons known to have been at the scene of the crime or who had legal access to the crime scene. This procedure eliminates all but the criminal's prints.

Techniques for Developing Latent Prints 4. Physical developer - a silver nitrate-based liquid reagent.  A dark image is produced when the silver nitrate solution reacts with salts in the latent print, in the presence of light. 5. Super Glue Fuming - a technique for visualizing latent fingerprints on non-porous surfaces by exposing them to cyanoacrylate vapors; named for the commercial product, super glue. 6. Fluorescent Reagents - the chemical DFO visualizes latent prints on porous materials when exposed to an alternate light source (Saferstein 408-409). 1. Powder Dusting - a powder of contrasting color to the surface being dusted is chosen.  Impressions on objects such as metal, plastic, glass, tile and other non-porous surfaces are easily processed with various fingerprint powders. 2. Iodine Fuming - vapor from warmed iodine crystals dissolves in the skin oils in a latent print, yielding a yellow brown print.  The developed latent prints are photographed immediately because they fade rapidly 3. Ninhydrin - a chemical reagent used to develop latent fingerprints on porous materials by reacting with amino acids in perspiration.

Inking A Person for Prints The steps for inking fingers and the steps for making impressions on the card are the same. Each finger is rolled through the ink on the glass and then that finger impression is rolled on the fingerprint card. All rolling should be made in single movements. Do not roll back and forth. The pressure should be just enough to apply an even coat of ink on the finger and a clear image on the card. After the procedure is complete, fill in the data on the fingerprint card. Sign the card or paper for identification. This signature is important in legal proceedings.

Fingerprint Record