Egftnjytyk

Part of a series on
Forensic science
Physiological Anthropology Biology Bloodstain pattern analysis Botany Dentistry DNA phenotyping DNA profiling Entomology Epidemiology Medicine Palynology Pathology Podiatry Toxicology
Social Psychiatry Psychology Psychotherapy Social work
Criminalistics Accounting Body identification Chemistry Facial reconstruction Fingerprint analysis Firearm examination Footwear evidence Forensic arts Profiling Gloveprint analysis Palmprint analysis Questioned document examination Vein matching
Digital forensics Computer exams Data analysis Database study Mobile devices Network analysis Photography Video analysis Audio analysis
Related disciplines Electrical engineering Engineering Fire investigation Fire accelerant detection Fractography Linguistics Materials engineering Polymer engineering Statistics Traffic collision reconstruction
Related articles Crime scene CSI effect Perry Mason syndrome Pollen calendar Skid mark Trace evidence Use of DNA in forensic entomology
Outline Category
v t e

A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger.^[1] The recovery of fingerprints from a crime scene is an important method of forensic science. Fingerprints are easily deposited on suitable surfaces (such as glass or metal or polished stone) by the natural secretions of sweat from the eccrine glands that are present in epidermal ridges. These are sometimes referred to as "Chanced Impressions".

In a wider use of the term, fingerprints are the traces of an impression from the friction ridges of any part of a human or other primate hand. A print from the sole of the foot can also leave an impression of friction ridges.

Deliberate impressions of fingerprints may be formed by ink or other substances transferred from the peaks of friction ridges on the skin to a relatively smooth surface such as a fingerprint card.^[2] Fingerprint records normally contain impressions from the pad on the last joint of fingers and thumbs, although fingerprint cards also typically record portions of lower joint areas of the fingers.

Human fingerprints are detailed, nearly unique, difficult to alter, and durable over the life of an individual, making them suitable as long-term markers of human identity. They may be employed by police or other authorities to identify individuals who wish to conceal their identity, or to identify people who are incapacitated or deceased and thus unable to identify themselves, as in the aftermath of a natural disaster. Fingerprint analysis, in use since the early 20th century, has led to many crimes being solved.^[3] This means that many criminals consider gloves essential.^[4][5] In 2015, the identification of sex by testing the fingerprint biochemical content (rather than visual pattern) has been reported.^[6][7]

Biology

A friction ridge is a raised portion of the epidermis on the digits (fingers and toes), the palm of the hand or the sole of the foot, consisting of one or more connected ridge units of friction ridge skin.^[1] These are sometimes known as "epidermal ridges" which are caused by the underlying interface between the dermal papillae of the dermis and the interpapillary (rete) pegs of the epidermis. These epidermal ridges serve to amplify vibrations triggered, for example, when fingertips brush across an uneven surface, better transmitting the signals to sensory nerves involved in fine texture perception.^[8] These ridges may also assist in gripping rough surfaces and may improve surface contact in wet conditions.^[9]

Types

Before computerization, manual filing systems were used in large fingerprint repositories. Manual classification systems were based on the general ridge patterns of several or all fingers (such as the presence or absence of circular patterns). This allowed the filing and retrieval of paper records in large collections based on friction ridge patterns alone. The most popular systems used the pattern class of each finger to form a key (a number) to assist lookup in a filing system. Classification systems include the Roscher system, the Juan Vucetich system, and the Henry Classification System. The Roscher system was developed in Germany and implemented in both Germany and Japan, the Vucetich system (developed by a Croatian-born Buenos Aires Police Officer) was developed in Argentina and implemented throughout South America, and the Henry system was developed in India and implemented in most English-speaking countries.^[10]

In the Henry system of classification, there are three basic fingerprint patterns: loop, whorl, and arch,^[11] which constitute 60–65%, 30–35%, and 5% of all fingerprints respectively.^{[citation needed]} There are also more complex classification systems that break down patterns even further, into plain arches or tented arches,^[10] and into loops that may be radial or ulnar, depending on the side of the hand toward which the tail points. Ulnar loops start on the pinky-side of the finger, the side closer to the ulna, the lower arm bone. Radial loops start on the thumb-side of the finger, the side closer to the radius. Whorls may also have sub-group classifications including plain whorls, accidental whorls, double loop whorls, peacock's eye, composite, and central pocket loop whorls.^[10]

Other common fingerprint patterns include the tented arch, the plain arch, and the central pocket loop.

The system used by most experts, although complex, is similar to the Henry System of Classification. It consists of five fractions, in which R
stands for right, L for left, i for index finger, m for middle finger, t for thumb, r for ring finger and p(pinky) for little finger. The fractions are as follows:
Ri/Rt + Rr/Rm + Lt/Rp + Lm/Li + Lp/Lr.
The numbers assigned to each print are based on whether or not they are whorls. A whorl in the first fraction is given a 16, the second an 8, the third a 4, the fourth a 2, and 0 to the last fraction. Arches and loops are assigned values of 0. Lastly, the numbers in the numerator and denominator are added up, using the scheme:

(Ri + Rr + Lt + Lm + Lp)/(Rt + Rm + Rp + Li + Lr)

and a 1 is added to both top and bottom, to exclude any possibility of division by zero. For example, if the right ring finger and the left index finger have whorls, the fractions would look like this:

0/0 + 8/0 + 0/0 + 0/2 + 0/0 + 1/1, and the calculation: (0 + 8 + 0 + 0 + 0 + 1)/(0 + 0 + 0 + 2 + 0 + 1) = 9/3 = 3.

Using this system reduces the number of prints that the print in question needs to be compared to. For example, the above set of prints would only need to be compared to other sets of fingerprints with a value of 3.^[12]

Arch 

Loop
(Right Loop) 

Whorl 

Arch
(Tented Arch) 

Dactyloscopy

The friction ridges on a finger

Fingerprint identification, known as dactyloscopy,^[13] or hand print identification, is the process of comparing two instances of friction ridge skin impressions (see Minutiae), from human fingers or toes, or even the palm of the hand or sole of the foot, to determine whether these impressions could have come from the same individual. The flexibility of friction ridge skin means that no two finger or palm prints are ever exactly alike in every detail; even two impressions recorded immediately after each other from the same hand may be slightly different.^{[citation needed]} Fingerprint identification, also referred to as individualization, involves an expert, or an expert computer system operating under threshold scoring rules, determining whether two friction ridge impressions are likely to have originated from the same finger or palm (or toe or sole).

An image of a fingerprint created by the friction ridge structure

An intentional recording of friction ridges is usually made with black printer's ink rolled across a contrasting white background, typically a white card. Friction ridges can also be recorded digitally, usually on a glass plate, using a technique called Live Scan. A "latent print" is the chance recording of friction ridges deposited on the surface of an object or a wall. Latent prints are invisible to the naked eye, whereas "patent prints" or "plastic prints" are viewable with the unaided eye. Latent prints are often fragmentary and require the use of chemical methods, powder, or alternative light sources in order to be made clear. Sometimes an ordinary bright flashlight will make a latent print visible.

When friction ridges come into contact with a surface that will take a print, material that is on the friction ridges such as perspiration, oil, grease, ink or blood, will be transferred to the surface. Factors which affect the quality of friction ridge impressions are numerous. Pliability of the skin, deposition pressure, slippage, the material from which the surface is made, the roughness of the surface and the substance deposited are just some of the various factors which can cause a latent print to appear differently from any known recording of the same friction ridges. Indeed, the conditions surrounding every instance of friction ridge deposition are unique and never duplicated. For these reasons, fingerprint examiners are required to undergo extensive training. The scientific study of fingerprints is called dermatoglyphics.

Types

Exemplar

Exemplar prints on paper using ink

Exemplar prints, or known prints, is the name given to fingerprints deliberately collected from a subject, whether for purposes of enrollment in a system or when under arrest for a suspected criminal offense. During criminal arrests, a set of exemplar prints will normally include one print taken from each finger that has been rolled from one edge of the nail to the other, plain (or slap) impressions of each of the four fingers of each hand, and plain impressions of each thumb. Exemplar prints can be collected using live scan or by using ink on paper cards.

Latent

Barely visible latent prints on a knife

Although the word latent means hidden or invisible, in modern usage for forensic science the term latent prints means any chance or accidental impression left by friction ridge skin on a surface, regardless of whether it is visible or invisible at the time of deposition. Electronic, chemical and physical processing techniques permit visualization of invisible latent print residues whether they are from natural sweat on the skin or from a contaminant such as motor oil, blood, ink, paint or some other form of dirt. The different types of fingerprint patterns, such as arch, loop and whorl, will be described below.

Latent prints may exhibit only a small portion of the surface of a finger and this may be smudged, distorted, overlapped by other prints from the same or from different individuals, or any or all of these in combination. For this reason, latent prints usually present an "inevitable source of error in making comparisons", as they generally "contain less clarity, less content, and less undistorted information than a fingerprint taken under controlled conditions, and much, much less detail compared to the actual patterns of ridges and grooves of a finger."^[14]

Patent

Patent prints are chance friction ridge impressions which are obvious to the human eye and which have been caused by the transfer of foreign material from a finger onto a surface. Some obvious examples would be impressions from flour and wet clay. Because they are already visible and have no need of enhancement they are generally photographed rather than being lifted in the way that latent prints are. An attempt to preserve the actual print is always made for later presentation in court, and there are many techniques used to do this. Patent prints can be left on a surface by materials such as ink, dirt, or blood.

Plastic

A plastic print is a friction ridge impression left in a material that retains the shape of the ridge detail. Although very few criminals would be careless enough to leave their prints in a lump of wet clay, this would make a perfect plastic print.^[15] Commonly encountered examples are melted candle wax, putty removed from the perimeter of window panes and thick grease deposits on car parts. Such prints are already visible and need no enhancement, but investigators must not overlook the potential that invisible latent prints deposited by accomplices may also be on such surfaces. After photographically recording such prints, attempts should be made to develop other non-plastic impressions deposited from sweat or other contaminants.

Electronic recording

There has been a newspaper report of a man selling stolen watches sending images of them on a mobile phone, and those images included parts of his hands in enough detail for police to be able to identify fingerprint patterns.^[16]

Recent studies found that the improving cameras with increasing resolution of smartphones might have a high impact on users’ security: The back-facing camera of a device can be used to capture an image of the user's index finger, which on smartphones using biometric means of authentication is often used to authenticate a user against the smartphone.^[17]

At the 31st Chaos Communication Congress, hardware hacker starbug presented how DSLRs with high resolution and equipped with a long focus lens can be used to capture images of hands, or more specifically, fingers in order to use them for spoofing.^[18]

Footprints

Friction ridge skin present on the soles of the feet and toes (plantar surfaces) is as unique in its ridge detail as are the fingers and palms (palmar surfaces). When recovered at crime scenes or on items of evidence, sole and toe impressions can be used in the same manner as finger and palm prints to effect identifications.^{[citation needed]} The footprints of infants, along with the thumb or index finger prints of mothers, are still commonly recorded in hospitals to assist in verifying the identity of infants. It is not uncommon for military records of flight personnel to include barefoot inked impressions. Friction ridge skin protected inside flight boots tends to survive the trauma of a plane crash (and accompanying fire) better than fingers.

Capture and detection

Live scan devices

Fingerprint being scanned

3D fingerprint^[19]

Fingerprint image acquisition is considered to be the most critical step in an automated fingerprint authentication system, as it determines the final fingerprint image quality, which has a drastic effect on the overall system performance. There are different types of fingerprint readers on the market, but the basic idea behind each is to measure the physical difference between ridges and valleys.

All the proposed methods can be grouped into two major families: solid-state fingerprint readers and optical fingerprint readers. The procedure for capturing a fingerprint using a sensor consists of rolling or touching with the finger onto a sensing area, which according to the physical principle in use (optical, ultrasonic, capacitive or thermal) captures the difference between valleys and ridges. When a finger touches or rolls onto a surface, the elastic skin deforms. The quantity and direction of the pressure applied by the user, the skin conditions and the projection of an irregular 3D object (the finger) onto a 2D flat plane introduce distortions, noise and inconsistencies in the captured fingerprint image. These problems result in inconsistent and non-uniform irregularities in the image.^[20] During each acquisition, therefore, the results of the imaging are different and uncontrollable. The representation of the same fingerprint changes every time the finger is placed on the sensor plate, increasing the complexity of any attempt to match fingerprints, impairing the system performance and consequently, limiting the widespread use of this biometric technology.

In order to overcome these problems, as of 2010, non-contact or touchless 3D fingerprint scanners have been developed.^[21][22] Acquiring detailed 3D information, 3D fingerprint scanners take a digital approach to the analog process of pressing or rolling the finger. By modelling the distance between neighboring points, the fingerprint can be imaged at a resolution high enough to record all the necessary detail.^[23]

Scanning dead or unconscious people

Placing the hand of a dead or unconscious person on a scanner to gain unauthorized access has become a common plot device. However, a MythBusters episode revealed that this doesn't work (at least with the scanners available to the program). But Adam Savage and Jamie Hyneman found a way to convert fingerprints lifted from the hand to a photographic form that the sensor would accept. For obvious reasons, they refuse to reveal the technique.

Latent detection

Use of fine powder and brush to reveal latent fingerprints

Fingerprints dusting of a burglary scene

In the 1930s criminal investigators in the United States first discovered the existence of latent fingerprints on the surfaces of fabrics, most notably on the insides of gloves discarded by perpetrators.^[24]

Since the late nineteenth century, fingerprint identification methods have been used by police agencies around the world to identify suspected criminals as well as the victims of crime. The basis of the traditional fingerprinting technique is simple. The skin on the palmar surface of the hands and feet forms ridges, so-called papillary ridges, in patterns that are unique to each individual and which do not change over time. Even identical twins (who share their DNA) do not have identical fingerprints. The best way to render latent fingerprints visible, so that they can be photographed, can be complex and may depend, for example, on the type of surfaces on which they have been left. It is generally necessary to use a ‘developer’, usually a powder or chemical reagent, to produce a high degree of visual contrast between the ridge patterns and the surface on which a fingerprint has been deposited.

Developing agents depend on the presence of organic materials or inorganic salts for their effectiveness, although the water deposited may also take a key role. Fingerprints are typically formed from the aqueous-based secretions of the eccrine glands of the fingers and palms with additional material from sebaceous glands primarily from the forehead. This latter contamination results from the common human behaviors of touching the face and hair. The resulting latent fingerprints consist usually of a substantial proportion of water with small traces of amino acids and chlorides mixed with a fatty, sebaceous component which contains a number of fatty acids and triglycerides. Detection of a small proportion of reactive organic substances such as urea and amino acids is far from easy.

Fingerprints at a crime scene may be detected by simple powders, or by chemicals applied in situ. More complex techniques, usually involving chemicals, can be applied in specialist laboratories to appropriate articles removed from a crime scene. With advances in these more sophisticated techniques, some of the more advanced crime scene investigation services from around the world were, as of 2010, reporting that 50% or more of the fingerprints recovered from a crime scene had been identified as a result of laboratory-based techniques.

A city fingerprint identification room.

Laboratory techniques

Although there are hundreds of reported techniques for fingerprint detection, many of these are only of academic interest and there are only around 20 really effective methods which are currently in use in the more advanced fingerprint laboratories around the world.

Some of these techniques, such as ninhydrin, diazafluorenone and vacuum metal deposition, show great sensitivity and are used operationally. Some fingerprint reagents are specific, for example ninhydrin or diazafluorenone reacting with amino acids. Others such as ethyl cyanoacrylate polymerisation, work apparently by water-based catalysis and polymer growth. Vacuum metal deposition using gold and zinc has been shown to be non-specific, but can detect fat layers as thin as one molecule.

More mundane methods, such as the application of fine powders, work by adhesion to sebaceous deposits and possibly aqueous deposits in the case of fresh fingerprints. The aqueous component of a fingerprint, whilst initially sometimes making up over 90% of the weight of the fingerprint, can evaporate quite quickly and may have mostly gone after 24 hours. Following work on the use of argon ion lasers for fingerprint detection,^[25] a wide range of fluorescence techniques have been introduced, primarily for the enhancement of chemically developed fingerprints; the inherent fluorescence of some latent fingerprints may also be detected. Fingerprints can for example be visualized in 3D and without chemicals by the use of infrared lasers.^[26]

A comprehensive manual of the operational methods of fingerprint enhancement was last published by the UK Home Office Scientific Development Branch in 2013 and is used widely around the world.^[27]

A technique proposed in 2007 aims to identify an individual's ethnicity, gender, and dietary patterns.^[28]

Research

The International Fingerprint Research Group (IFRG) which meets biennially, consists of members of the leading fingerprint research groups from Europe, the US, Canada, Australia and Israel and leads the way in the development, assessment and implementation of new techniques for operational fingerprint detection.

One problem for the early twenty-first century is the fact that the organic component of any deposited material is readily destroyed by heat, such as occurs when a gun is fired or a bomb is detonated, when the temperature may reach as high as 500 °C. Encouragingly, however, the non-volatile inorganic component of eccrine secretion has been shown to remain intact even when exposed to temperatures as high as 600 °C.

A technique has been developed that enables fingerprints to be visualised on metallic and electrically conductive surfaces without the need to develop the prints first.^[29] This technique involves the use of an instrument called a scanning Kelvin probe (SKP), which measures the voltage, or electrical potential, at pre-set intervals over the surface of an object on which a fingerprint may have been deposited. These measurements can then be mapped to produce an image of the fingerprint. A higher resolution image can be obtained by increasing the number of points sampled, but at the expense of the time taken for the process. A sampling frequency of 20 points per mm is high enough to visualise a fingerprint in sufficient detail for identification purposes and produces a voltage map in 2–3 hours. As of 2010, this technique had been shown to work effectively on a wide range of forensically important metal surfaces including iron, steel and aluminium. While initial experiments were performed on flat surfaces, the technique has been further developed to cope with irregular or curved surfaces, such as the warped cylindrical surface of fired cartridge cases. Research during 2010 at Swansea University has found that physically removing a fingerprint from a metal surface, for example by rubbing with a tissue, does not necessarily result in the loss of all fingerprint information from that surface. The reason for this is that the differences in potential that are the basis of the visualisation are caused by the interaction of inorganic salts in the fingerprint deposit and the metal surface and begin to occur as soon as the finger comes into contact with the metal, resulting in the formation of metal-ion complexes that cannot easily be removed.

Cartridge case with an applied fingerprint

Scanning Kelvin probe scan of the same cartridge case with the fingerprint detected. The Kelvin probe can easily cope with the 3D curvature of the cartridge case, increasing the versatility of the technique.

Another problem for the early twenty-first century is that during crime scene investigations, a decision has to be made at an early stage whether to attempt to retrieve fingerprints through the use of developers or whether to swab surfaces in an attempt to salvage material for DNA profiling. The two processes are mutually incompatible, as fingerprint developers destroy material that could potentially be used for DNA analysis, and swabbing is likely to make fingerprint identification impossible.

The application of the new scanning Kelvin probe (SKP) fingerprinting technique, which makes no physical contact with the fingerprint and does not require the use of developers, has the potential to allow fingerprints to be recorded whilst still leaving intact material that could subsequently be subjected to DNA analysis. A forensically usable prototype was under development at Swansea University during 2010, in research that was generating significant interest from the British Home Office and a number of different police forces across the UK, as well as internationally. The hope is that this instrument could eventually be manufactured in sufficiently large numbers to be widely used by forensic teams worldwide.^[30][31]

Disappearance of children's latent prints

In 1995, researchers at the Oak Ridge National Laboratory, at the instigation of Detective Art Bohanan of the Knoxville Police Department, discovered that children's fingerprints are considerably more short-lived than adult fingerprints.^[32] The rapid disappearance of children's fingerprints was attributed to a lack of the more waxy oils that become present at the onset of puberty. The lighter fatty acids of children's fingerprints evaporate within a few hours. As of 2010, researchers at Oak Ridge National Laboratory are investigating techniques to capture these lost fingerprints.

Detection of drug use

The secretions, skin oils and dead cells in a human fingerprint contain residues of various chemicals and their metabolites present in the body. These can be detected and used for forensic purposes. For example, the fingerprints of tobacco smokers contain traces of cotinine, a nicotine metabolite; they also contain traces of nicotine itself. Caution should be used, as its presence may be caused by mere contact of the finger with a tobacco product.

By treating the fingerprint with gold nanoparticles with attached cotinine antibodies, and then subsequently with a fluorescent agent attached to cotinine antibodies, the fingerprint of a smoker becomes fluorescent; non-smokers' fingerprints stay dark.

The same approach, as of 2010, is being tested for use in identifying heavy coffee drinkers, cannabis smokers, and users of various other drugs.^[33][34]

In 2008, British researchers developed methods of identifying users of marijuana, cocaine and methadone from their fingerprint residues.^[35]

United States databases and compression

In the United States, the FBI manages a fingerprint identification system and database called the Integrated Automated Fingerprint Identification System (IAFIS), which currently holds the fingerprints and criminal records of over 51 million criminal record subjects and over 1.5 million civil (non-criminal) fingerprint records. US Visit currently holds a repository of the fingerprints of over 50 million non-US citizens, primarily in the form of two-finger records. In 2008, US Visit hoped to have changed over to a system recording FBI-standard ten-print records.

Most American law enforcement agencies use Wavelet Scalar Quantization (WSQ), a wavelet-based system for efficient storage of compressed fingerprint images at 500 pixels per inch (ppi). WSQ was developed by the FBI, the Los Alamos National Lab, and the National Institute for Standards and Technology (NIST). For fingerprints recorded at 1000 ppi spatial resolution, law enforcement (including the FBI) uses JPEG 2000 instead of WSQ.

A city fingerprint identification office

Validity

The validity of forensic fingerprint evidence has been challenged by academics, judges and the media. While fingerprint identification was an improvement on earlier anthropometric systems, the subjective nature of matching, despite a very low error rate, has made this forensic practice controversial.^[36]

Certain specific criticisms are now being accepted by some leaders of the forensic fingerprint community, providing an incentive to improve training and procedures.

Criticism

The words "reliability" and "validity" have specific meanings to the scientific community. Reliability means that successive tests bring the same results. Validity means that these results are judged to accurately reflect the external criteria being measured.

Although experts are often more comfortable relying on their instincts, this reliance does not always translate into superior predictive ability. For example, in the popular Analysis, Comparison, Evaluation, and Verification (ACE-V) paradigm for fingerprint identification, the verification stage, in which a second examiner confirms the assessment of the original examiner, may increase the consistency of the assessments. But while the verification stage has implications for the reliability of latent print comparisons, it does not assure their validity.

— Sandy L Zabell, ^[37]

The few tests that have been made of the validity of forensic fingerprinting have not been supportive of the method.

"Despite the absence of objective standards, scientific validation, and adequate statistical studies, a natural question to ask is how well fingerprint examiners actually perform. Proficiency tests do not validate a procedure per se, but they can provide some insight into error rates. In 1995, the Collaborative Testing Service (CTS) administered a proficiency test that, for the first time, was "designed, assembled, and reviewed" by the International Association for Identification (IAI). The results were disappointing. Four suspect cards with prints of all ten fingers were provided together with seven latents. Of 156 people taking the test, only 68 (44%) correctly classified all seven latents. Overall, the tests contained a total of 48 incorrect identifications. David Grieve, the editor of the Journal of Forensic Identification, describes the reaction of the forensic community to the results of the CTS test as ranging from "shock to disbelief", and added:

'Errors of this magnitude within a discipline singularly admired and respected for its touted absolute certainty as an identification process have produced chilling and mind-numbing realities. Thirty-four participants, an incredible 22% of those involved, substituted presumed but false certainty for truth. By any measure, this represents a profile of practice that is unacceptable and thus demands positive action by the entire community.'

What is striking about these comments is that they do not come from a critic of the fingerprint community, but from the editor of one of its premier publications."

— Sandy L Zabell, ^[37]

Investigations have been conducted into whether experts can objectively focus on feature information in fingerprints without being misled by extraneous information, such as context.^[38] Fingerprints that have previously been examined and assessed by latent print experts to make a positive identification of suspects have then been re-presented to those same experts in a new context which makes it likely that there will be no match. Within this new context, most of the fingerprint experts made different judgments, thus contradicting their own previous identification decisions.^[38]

Complaints have been made that there have been no published, peer-reviewed studies directly examining the extent to which people can correctly match fingerprints to one another.^[39] Experiments have been carried out using naïve undergraduates to match images of fingerprints. The results of these experiments demonstrate that people can identify fingerprints quite well, and that matching accuracy can vary as a function of both source finger type and image similarity.^[39]

Defense

Fingerprints collected at a crime scene, or on items of evidence from a crime, have been used in forensic science to identify suspects, victims and other persons who touched a surface. Fingerprint identification emerged as an important system within police agencies in the late 19th century, when it replaced anthropometric measurements as a more reliable method for identifying persons having a prior record, often under a false name, in a criminal record repository.^[13] In modern times, researchers can find traces of addictive drugs on just a fingerprint.^[40]

Track record

Fingerprinting has served all governments worldwide during the past 100 years or so to provide identification of criminals. Fingerprints are the fundamental tool in every police agency for the identification of people with a criminal history.^[13] They remain the most commonly gathered forensic evidence worldwide, and in most jurisdictions fingerprint examination is more common than all other forensic examination casework combined. Moreover, it continues to expand, with tens of thousands of people added to fingerprint repositories daily in America alone — far more than other forensic databases.^{[citation needed]}

Professional certification

Fingerprinting was the basis upon which the first forensic professional organization was formed, the International Association for Identification (IAI), in 1915.^[41] The first professional certification program for forensic scientists was established in 1977, the IAI's Certified Latent Print Examiner program, which issued certificates to those meeting stringent criteria and had the power to revoke certification where an individual's performance warranted it.^[42] Other forensic disciplines have followed suit and established their own certification programs.^[42]

Errors

Brandon Mayfield and the Madrid bombing

Brandon Mayfield is an Oregon lawyer who was identified as a participant in the 2004 Madrid train bombings based on a fingerprint match by the FBI.^[43] The FBI Latent Print Unit processed a fingerprint collected in Madrid and reported a "100 percent positive" match against one of the 20 fingerprint candidates returned in a search response from their Integrated Automated Fingerprint Identification System. The FBI initially called it an "absolutely incontrovertible match". Subsequently, however, Spanish National Police examiners suggested that the print did not match Mayfield and after two weeks, identified another man whom they claimed the fingerprint did belong to. The FBI acknowledged their error, and a judge released Mayfield, who had spent two weeks in police custody, in May 2004.^[43] In January 2006, a U.S. Justice Department report was released which criticized the FBI for sloppy work but exonerated them of some more serious allegations. The report found that the misidentification had been due to a misapplication of methodology by the examiners involved: Mayfield is an American-born convert^[43] to Islam and his wife is an Egyptian immigrant,^[43] but these are not factors that should have affected fingerprint search technology.

On November 29, 2006, the FBI agreed to pay Brandon Mayfield US$2 million in compensation.^[43] The judicial settlement allowed Mayfield to continue a suit regarding certain other government practices surrounding his arrest and detention. The formal apology stated that the FBI, which erroneously linked him to the 2004 Madrid bombing through a fingerprinting mistake, had taken steps to "ensure that what happened to Mr. Mayfield and the Mayfield family does not happen again."^[43]

René Ramón Sánchez

René Ramón Sánchez, a legal Dominican Republic immigrant to the US, was arrested on July 15, 1995, on a charge of driving while intoxicated. His fingerprints were mistakenly placed on a card containing the name, Social Security number and other data for one Leo Rosario, who was being processed at the same time. Leo Rosario had been arrested for selling cocaine to an undercover police officer. On October 11, 2000, while returning from a visit to relatives in the Dominican Republic, René was misidentified as Leo Rosario at John F. Kennedy International Airport in New York and arrested. Even though he did not match the physical description of Rosario, the erroneously cataloged fingerprints were considered to be more reliable.^[44]

Shirley McKie

Shirley McKie was a police detective in 1997 when she was accused of leaving her thumb print inside a house in Kilmarnock, Scotland, where Marion Ross had been murdered. Although McKie denied having been inside the house, she was arrested in a dawn raid the following year and charged with perjury. The only evidence the prosecution had was this thumb print allegedly found at the murder scene. Two American experts testified on her behalf at her trial in May 1999 and she was found not guilty. The Scottish Criminal Record Office (SCRO) would not admit any error, although Scottish first minister Jack McConnell later said it had been an "honest mistake".

On February 7, 2006, McKie was awarded £750,000 in compensation from the Scottish Executive and the Scottish Criminal Record Office.^[45] Controversy continued to surround the McKie case and the Fingerprint Inquiry into the affair finished taking evidence in November 2009.^{[needs update][46]} The Inquiry Report was published on 11 December 2011.^[47]

Stephan Cowans

Stephan Cowans was convicted of attempted murder in 1997 after he was accused of shooting a police officer whilst fleeing a robbery in Roxbury, Massachusetts. He was implicated in the crime by the testimony of two witnesses, one of whom was the victim. There was also a fingerprint on a glass mug from which the assailant had drunk some water and experts testified that the fingerprint belonged to Cowans. He was found guilty and sent to prison for 35 years. Whilst in prison, Cowans earned money cleaning up biohazards^{[clarification needed]} until he could afford to have the evidence against him tested for DNA. The DNA did not match his and he was released. He had already served six years in prison when he was released on January 23, 2004.^[48] Cowans died on October 25, 2007.^[48]

Craig D. Harvey

In April 1993, in the New York State Police Troop C scandal, Craig D. Harvey, a New York State Police trooper, was charged with fabricating evidence. Harvey admitted he and another trooper lifted fingerprints from items the suspect, John Spencer, touched while in Troop C headquarters during booking. He attached the fingerprints to evidence cards and later claimed that he had pulled the fingerprints from the scene of the murder. The forged evidence was presented during John Spencer's trial and his subsequent conviction resulted in a term of 50 years to life in prison at his sentencing.^[49] Three state troopers were found guilty of fabricating fingerprint evidence and served prison sentences.^[50]

History

Antiquity and the medieval period

Fingerprints have been found on ancient Babylonian clay tablets, seals, and pottery.^{[51][52][53][54]} They have also been found on the walls of Egyptian tombs and on Minoan, Greek, and Chinese^[55] pottery, as well as on bricks and tiles from ancient Babylon and Rome. Some of these fingerprints were deposited unintentionally by the potters and masons as a natural consequence of their work, and others were made in the process of adding decoration. However, on some pottery, fingerprints have been impressed so deeply into the clay that they were possibly intended to serve as an identifying mark by the maker.

Fingerprints were used as signatures in ancient Babylon in the second millennium BCE.^[56] In order to protect against forgery, parties to a legal contract would impress their fingerprints into a clay tablet on which the contract had been written. In Ancient India some texts called Naadi were written by a Rishi called Agastya where the text is said to predict the past, present and the future lives of all humans from thumb print.the Naadi palm leaves are located based on the thumb impressions (right for men, left for women).^[57] This ancient Indian system of astrology was called Nadi astrology. By 246 BCE, Chinese officials were impressing their fingerprints into the clay seals used to seal documents. With the advent of silk and paper in China, parties to a legal contract impressed their handprints on the document. Sometime before 851 CE, an Arab merchant in China, Abu Zayd Hasan, witnessed Chinese merchants using fingerprints to authenticate loans.^[58] By 702, Japan allowed illiterate petitioners seeking a divorce to "sign" their petitions with a fingerprint.^[59][60]

Although ancient peoples probably did not realize that fingerprints could uniquely identify individuals,^[61] references from the age of the Babylonian king Hammurabi (reigned 1792-1750 BCE) indicate that law officials would take the fingerprints of people who had been arrested.^[62] During China's Qin Dynasty, records have shown that officials took hand prints, foot prints as well as finger prints as evidence from a crime scene.^[63] In China, around 300 CE, handprints were used as evidence in a trial for theft. By 650, the Chinese historian Kia Kung-Yen remarked that fingerprints could be used as a means of authentication.^[64] In his Jami al-Tawarikh (Universal History), the Persian physician Rashid-al-Din Hamadani (also known as "Rashideddin", 1247–1318) refers to the Chinese practice of identifying people via their fingerprints, commenting: "Experience shows that no two individuals have fingers exactly alike."^[65] In Persia at this time, government documents may have been authenticated with thumbprints.^{[citation needed]}

Europe in the 17th and 18th centuries

In 1665, the Italian physician Marcello Malpighi (1628–1694) briefly mentioned, in his De externo tactus organo anatomica observatio, the existence of patterns of ridges and sweat glands on the fingertips.^[66] In 1684, the English physician, botanist, and microscopist Nehemiah Grew (1641–1712) published the first scientific paper to describe the ridge structure of the skin covering the fingers and palms.^[67] In 1685, the Dutch physician Govard Bidloo (1649–1713) published a book on anatomy which also illustrated the ridge structure of the fingers.^[68] A century later, in 1788, the German anatomist Johann Christoph Andreas Mayer (1747–1801) recognized that fingerprints are unique to each individual.^[69][70]

Modern era

Fingerprints taken by William Herschel 1859/60

Fingerprints used instead of signatures on an Indian legal document of 1952.

Jan Evangelista Purkyně or Purkinje (1787–1869), a Czech physiologist and professor of anatomy at the University of Breslau, published a thesis in 1823 discussing 9 fingerprint patterns, but he did not mention any possibility of using fingerprints to identify people.^[71]
In 1840, following the murder of Lord William Russell, a provincial doctor, Robert Blake Overton, wrote to Scotland Yard suggesting checking for fingerprints but the suggestion, though followed up, did not lead to their routine use by the police for another 50 years.^[72]
Some years later, the German anatomist Georg von Meissner (1829–1905) studied friction ridges,^[73] and five years after this, in 1858, Sir William James Herschel initiated fingerprinting in India. In 1877 at Hooghly (near Calcutta) he instituted the use of fingerprints on contracts and deeds to prevent the then-rampant repudiation of signatures^[74] and he registered government pensioners' fingerprints to prevent the collection of money by relatives after a pensioner's death.^[75] Herschel also fingerprinted prisoners upon sentencing to prevent various frauds that were attempted in order to avoid serving a prison sentence.

In 1863, Paul-Jean Coulier (1824–1890), professor for chemistry and hygiene at the medical and pharmaceutical school of the Val-de-Grâce military hospital in Paris, discovered that iodine fumes can reveal fingerprints on paper.^[76]

In 1880, Dr. Henry Faulds, a Scottish surgeon in a Tokyo hospital, published his first paper on the subject in the scientific journal Nature, discussing the usefulness of fingerprints for identification and proposing a method to record them with printing ink. He also established their first classification and was also the first to identify fingerprints left on a vial.^[77] Returning to the UK in 1886, he offered the concept to the Metropolitan Police in London but it was dismissed at that time.^[78] Faulds wrote to Charles Darwin with a description of his method but, too old and ill to work on it, Darwin gave the information to his cousin, Francis Galton, who was interested in anthropology. Having been thus inspired to study fingerprints for ten years, Galton published a detailed statistical model of fingerprint analysis and identification and encouraged its use in forensic science in his book Finger Prints. He had calculated that the chance of a "false positive" (two different individuals having the same fingerprints) was about 1 in 64 billion.^[79]

Juan Vucetich, an Argentine chief police officer, created the first method of recording the fingerprints of individuals on file, associating these fingerprints to the anthropometric system of Alphonse Bertillon, who had created, in 1879, a system to identify individuals by anthropometric photographs and associated quantitative descriptions. In 1892, after studying Galton's pattern types, Vucetich set up the world's first fingerprint bureau. In that same year, Francisca Rojas of Necochea, was found in a house with neck injuries, whilst her two sons were found dead with their throats cut. Rojas accused a neighbour, but despite brutal interrogation, this neighbour would not confess to the crimes. Inspector Alvarez, a colleague of Vucetich, went to the scene and found a bloody thumb mark on a door. When it was compared with Rojas' prints, it was found to be identical with her right thumb. She then confessed to the murder of her sons.

Women clerical employees of the Los Angeles Police Department being fingerprinted and photographed in 1928.

A Fingerprint Bureau was established in Calcutta (Kolkata), India, in 1897, after the Council of the Governor General approved a committee report that fingerprints should be used for the classification of criminal records. Working in the Calcutta Anthropometric Bureau were Azizul Haque and Hem Chandra Bose. Haque and Bose were Indian fingerprint experts who have been credited with the primary development of a fingerprint classification system eventually named after their supervisor, Sir Edward Richard Henry.^[80][81] The Henry Classification System, co-devised by Haque and Bose, was accepted in England and Wales when the first United Kingdom Fingerprint Bureau was founded in Scotland Yard, the Metropolitan Police headquarters, London, in 1901. Sir Edward Richard Henry subsequently achieved improvements in dactyloscopy.

In the United States, Dr. Henry P. DeForrest used fingerprinting in the New York Civil Service in 1902, and by 1906, New York City Police Department Deputy Commissioner Joseph A. Faurot, an expert in the Bertillon system and a finger print advocate at Police Headquarters, introduced the fingerprinting of criminals to the United States.

The Scheffer case of 1902 is the first case of the identification, arrest and conviction of a murderer based upon fingerprint evidence. Alphonse Bertillon identified the thief and murderer Scheffer, who had previously been arrested and his fingerprints filed some months before, from the fingerprints found on a fractured glass showcase, after a theft in a dentist's apartment where the dentist's employee was found dead. It was able to be proved in court that the fingerprints had been made after the showcase was broken.^[82] A year later, Alphonse Bertillon created a method of getting fingerprints off smooth surfaces and took a further step in the advance of dactyloscopy.

Many criminals wear gloves to avoid leaving fingerprints. However, the gloves themselves can leave prints that are as unique as human fingerprints. After collecting glove prints, law enforcement can match them to gloves that they have collected as evidence or to prints collected at other crime scenes.^[83] In many jurisdictions the act of wearing gloves itself while committing a crime can be prosecuted as an inchoate offense.^[84]

As many offenses are crimes of opportunity, assailants do not always possess gloves when they commit their illegal activities. Thus, assailants have been observed using pulled-down sleeves, pieces of clothing, and other fabrics to handle objects and touch surfaces while committing crimes.^{[85][86][better source needed]}

Privacy

Fingerprinting of children

Various schools have implemented fingerprint locks or made a record of children's fingerprints. In the United Kingdom there have been fingerprint locks in Holland Park School in London,^[87] and children's fingerprints are stored on databases.^[88] There have also been instances in Belgium, at the école Marie-José in Liège,^[89][90] in France and in Italy. The non-governmental organization (NGO) Privacy International in 2002 made the cautionary announcement that tens of thousands of UK school children were being fingerprinted by schools, often without the knowledge or consent of their parents.^[91] That same year, the supplier Micro Librarian Systems, which uses a technology similar to that used in US prisons and the German military, estimated that 350 schools throughout Britain were using such systems to replace library cards.^[91] By 2007, it was estimated that 3,500 schools were using such systems.^[92] Under the United Kingdom Data Protection Act, schools in the UK do not have to ask parental consent to allow such practices to take place. Parents opposed to fingerprinting may only bring individual complaints against schools.^[93] In response to a complaint which they are continuing to pursue, in 2010 the European Commission expressed 'significant concerns' over the proportionality and necessity of the practice and the lack of judicial redress, indicating that the practice may break the European Union data protection directive.^[94]

In Belgium, the practice of taking fingerprints from children gave rise to a question in Parliament on February 6, 2007, by Michel de La Motte (Humanist Democratic Centre) to the Education Minister Marie Arena, who replied that it was legal provided that the school did not use them for external purposes, or to survey the private life of children.^[95] At Angers in France, Carqueiranne College in the Var won the Big Brother Award for 2005 and the Commission nationale de l'informatique et des libertés (CNIL), the official organisation in charge of the protection of privacy in France, declared the measures it had introduced "disproportionate."^[96]

In March 2007, the British government was considering fingerprinting all children aged 11 to 15 and adding the prints to a government database as part of a new passport and ID card scheme and disallowing opposition for privacy concerns. All fingerprints taken would be cross-checked against prints from 900,000 unsolved crimes. Shadow Home secretary David Davis called the plan "sinister".^[92] An Early Day Motion which called on the UK Government to conduct a full and open consultation with stakeholders about the use of biometrics in schools, secured the support of 85 Members of Parliament (Early Day Motion 686).^[97] Following the establishment in the United Kingdom of a Conservative and Liberal Democratic coalition government in May 2010, the ID card scheme was scrapped.^[98]

Serious concerns about the security implications of using conventional biometric templates in schools have been raised by a number of leading IT security experts,^[99] one of whom has voiced the opinion that "it is absolutely premature to begin using 'conventional biometrics' in schools".^[100] The vendors of biometric systems claim that their products bring benefits to schools such as improved reading skills, decreased wait times in lunch lines and increased revenues.^[101] They do not cite independent research to support this view. One education specialist wrote in 2007: "I have not been able to find a single piece of published research which suggests that the use of biometrics in schools promotes healthy eating or improves reading skills amongst children... There is absolutely no evidence for such claims".^[102] The Ottawa Police in Canada have advised parents who fear their children may be kidnapped, to fingerprint their children.^[103]

Other uses

Welfare claimants

It has been alleged that taking the fingerprints of welfare recipients as identification serves as a social stigma that evokes cultural images associated with the processing of criminals.^[104]

Log-in authentication and other locks

Since 2000, electronic fingerprint readers have been introduced for security applications such as log-in authentication for the identification of computer users. However, some less sophisticated devices have been discovered to be vulnerable to quite simple methods of deception, such as fake fingerprints cast in gels. In 2006, fingerprint sensors gained popularity in the notebook PC market. Built-in sensors in laptops, such as ThinkPads, VAIO, HP Pavilion and EliteBook laptops, and others also double as motion detectors for document scrolling, like the scroll wheel.

Following the release of the iPhone 5S model, a group of German hackers announced on September 21, 2013, that they had bypassed Apple's new Touch ID fingerprint sensor by photographing a fingerprint from a glass surface and using that captured image as verification. The spokesman for the group stated: "We hope that this finally puts to rest the illusions people have about fingerprint biometrics. It is plain stupid to use something that you can't change and that you leave everywhere every day as a security token."^[105]

Electronic registration and library access

Fingerprints and, to a lesser extent, iris scans can be used to validate electronic registration, cashless catering, and library access. By 2007, this practice was particularly widespread in UK schools,^[106] and it was also starting to be adopted in some states in the US.^{[citation needed]}

Absence or mutilation of fingerprints

A very rare medical condition, adermatoglyphia, is characterized by the absence of fingerprints. Affected persons have completely smooth fingertips, palms, toes and soles, but no other medical signs or symptoms.^[107] A 2011 study indicated that adermatoglyphia is caused by the improper expression of the protein SMARCAD1.^[108] The condition has been called immigration delay disease by the researchers describing it, because the congenital lack of fingerprints causes delays when affected persons attempt to prove their identity while traveling.^[107] Only five families with this condition have been described as of 2011.^[109]

People with Naegeli–Franceschetti–Jadassohn syndrome and dermatopathia pigmentosa reticularis, which are both forms of ectodermal dysplasia, also have no fingerprints. Both of these rare genetic syndromes produce other signs and symptoms as well, such as thin, brittle hair.

The anti-cancer medication capecitabine may cause the loss of fingerprints.^[110] Swelling of the fingers, such as that caused by bee stings, will in some cases cause the temporary disappearance of fingerprints, though they will return when the swelling recedes.

Since the elasticity of skin decreases with age, many senior citizens have fingerprints that are difficult to capture. The ridges get thicker; the height between the top of the ridge and the bottom of the furrow gets narrow, so there is less prominence.^[111]

Fingerprints can be erased permanently and this can potentially be used by criminals to reduce their chance of conviction. Erasure can be achieved in a variety of ways including simply burning the fingertips, using acids and advanced techniques such as plastic surgery.^{[112][113][114][115][116]}John Dillinger burned his fingers with acid, but prints taken during a previous arrest and upon death still exhibited almost complete relation to one another.^[117]

Fingerprint recognition

Fingerprint authentication refers to the automated method of verifying a match between two human fingerprints. Fingerprints are one of many forms of biometrics used to identify individuals and verify their identity.

The analysis of fingerprints for matching purposes generally requires the comparison of several features of the print pattern. These include patterns, which are aggregate characteristics of ridges, and minutia points, which are unique features found within the patterns.^[1] It is also necessary to know the structure and properties of human skin in order to successfully employ some of the imaging technologies.

Patterns

The three basic patterns of fingerprint ridges are the arch, loop, and whorl:

• arch: The ridges enter from one side of the finger, rise in the center forming an arc, and then exit the other side of the finger.


• loop: The ridges enter from one side of a finger, form a curve, and then exit on that same side.


• 
  whorl: Ridges form circularly around a central point on the finger.

Scientists have found that family members often share the same general fingerprint patterns, leading to the belief that these patterns are inherited.^[2]

Fingerprint processing

Fingerprint processing has three primary functions: enrollment, searching and verification. Among these functions, enrollment which captures fingerprint image from the sensor plays an important role. A reason is that the way people put their fingerprints on a mirror to scan can affect to the result in the searching and verifying process. Regarding to verification function, there are several techniques to match fingerprints such as correlation-based matching, minutiae-based matching, ridge feature-based matching and minutiae-based algorithm. However, the most popular algorithm was minutiae based matching algorithm due to its efficiency and accuracy.

Minutiae features

The major minutia features of fingerprint ridges are ridge ending, bifurcation, and short ridge (or dot). The ridge ending is the point at which a ridge terminates. Bifurcations are points at which a single ridge splits into two ridges. Short ridges (or dots) are ridges which are significantly shorter than the average ridge length on the fingerprint. Minutiae and patterns are very important in the analysis of fingerprints since no two fingers have been shown to be identical.^[3]

Illustrations

Ridge ending

Bifurcation

Short ridge (dot)

Defeats

In 2002, a Japanese cryptographer demonstrated how fingerprint recognition devices can be fooled 4 out of 5 times using a combination of low cunning, cheap kitchen supplies and a digital camera.^[118]

Latent fingerprints from a glass were enhanced with super-glue fumes in the form of cyanoacrylate adhesive and photographed. An image editor was then used to improve the contrast and the result printed onto a transparency sheet. The sheet was used to expose a UV sensitive printed-circuit board and etched. The copper imprint were then used for a plastic finger mold. A gelatin found in Gummy bears was molded into a fake finger.^[118] Eleven commercially available fingerprint biometric systems took the fake finger as the real thing. Noted cryptographer Bruce Schneier said "The results are enough to scrap the systems completely, and to send the various fingerprint biometric companies packing."^[118]

Fingerprint recognition in electronic devices

Two of the first smartphone manufacturers to integrate fingerprint recognition into their phones were Motorola with the Atrix 4G in 2011, and Apple with the iPhone 5S on 10 September 2013. One month after, HTC launched the One Max, which also included fingerprint recognition. In April 2014, Samsung released the Galaxy S5, which integrated a fingerprint sensor on the home button.^[119]

Since December 2015, cheaper smartphones with fingerprint recognition have been released, such as the $100 UMI Fair.^[119]Samsung also recently introduced fingerprint sensors to its mid-range A-series smartphones.

On 25 September 2015 with iPhone 6s, two years after introduction of its first fingerprint scanner in the iPhone 5S, Apple introduced a new generation fingerprint scanner claiming faster response times. In August 2016, OPPO claimed 0,22s response time in its Oppo F1's model.^[120]

Hewlett Packard, Asus, Huawei, Lenovo and Apple are using fingerprint reader in their laptops.^{[121][122][123]}Synaptics says the SecurePad sensor is now available for OEMs to start building into their laptops.^[124]

Fingerprint sensors

A fingerprint sensor is an electronic device used to capture a digital image of the fingerprint pattern. The captured image is called a live scan. This live scan is digitally processed to create a biometric template (a collection of extracted features) which is stored and used for matching. Many technologies have been used including optical, capacitive, RF, thermal, piezoresistive, ultrasonic, piezoelectric, MEMS.^[125] This is an overview of some of the more commonly used fingerprint sensor technologies.

Optical

Optical fingerprint imaging involves capturing a digital image of the print using visible light. This type of sensor is, in essence, a specialized type of digital camera. The top layer of the sensor, where the finger is placed, is known as the touch surface. Beneath this layer is a light-emitting phosphor layer which illuminates the surface of the finger. The light reflected from the finger passes through the phosphor layer to an array of solid state pixels (a charge-coupled device) which captures a visual image of the fingerprint. A scratched or dirty touch surface can cause a bad image of the fingerprint. A disadvantage of this type of sensor is the fact that the imaging capabilities are affected by the quality of skin on the finger. For instance, a dirty or marked finger is difficult to image properly. Also, it is possible for an individual to erode the outer layer of skin on the fingertips to the point where the fingerprint is no longer visible. It can also be easily fooled by an image of a fingerprint if not coupled with a "live finger" detector. However, unlike capacitive sensors, this sensor technology is not susceptible to electrostatic discharge damage.^[4]

Fingerprints can be read from a distance.^[126]

Ultrasonic

Ultrasonic sensors make use of the principles of medical ultrasonography in order to create visual images of the fingerprint. Unlike optical imaging, ultrasonic sensors use very high frequency sound waves to penetrate the epidermal layer of skin. The sound waves are generated using piezoelectric transducers and reflected energy is also measured using piezoelectric materials. Since the dermal skin layer exhibits the same characteristic pattern of the fingerprint, the reflected wave measurements can be used to form an image of the fingerprint. This eliminates the need for clean, undamaged epidermal skin and a clean sensing surface.^[5][127] LeEco became the first company to introduce this in Smartphone.^[128]

Capacitance

Capacitance sensors use principles associated with capacitance in order to form fingerprint images. In this method of imaging, the sensor array pixels each act as one plate of a parallel-plate capacitor, the dermal layer (which is electrically conductive) acts as the other plate, and the non-conductive epidermal layer acts as a dielectric.

Apple's Touch ID uses a capacitance fingerprint sensor.^[129]

Passive capacitance

A passive capacitance sensor use the principle outlined above to form an image of the fingerprint patterns on the dermal layer of skin. Each sensor pixel is used to measure the capacitance at that point of the array. The capacitance varies between the ridges and valleys of the fingerprint due to the fact that the volume between the dermal layer and sensing element in valleys contains an air gap. The dielectric constant of the epidermis and the area of the sensing element are known values. The measured capacitance values are then used to distinguish between fingerprint ridges and valleys.^[6]

Active capacitance

Active capacitance sensors use a charging cycle to apply a voltage to the skin before measurement takes place. The application of voltage charges the effective capacitor. The electric field between the finger and sensor follows the pattern of the ridges in the dermal skin layer. On the discharge cycle, the voltage across the dermal layer and sensing element is compared against a reference voltage in order to calculate the capacitance. The distance values are then calculated mathematically, and used to form an image of the fingerprint.^[7] Active capacitance sensors measure the ridge patterns of the dermal layer like the ultrasonic method. Again, this eliminates the need for clean, undamaged epidermal skin and a clean sensing surface.^[7]

Algorithms

Matching algorithms are used to compare previously stored templates of fingerprints against candidate fingerprints for authentication purposes. In order to do this either the original image must be directly compared with the candidate image or certain features must be compared.^[8]

Pre-processing

Pre-processing helped enhancing the quality of an image by filtering and removing unnecessary noises. The minutiae based algorithm only worked effectively in 8-bit gray scale fingerprint image. A reason was that an 8-bit gray fingerprint image was a fundamental base to convert the image to 1-bit image with value 0 for ridges and value 1 for furrows. As a result, the ridges were highlighted with black color while the furrows were highlighted with white color. This process partly removed some noises in an image and helped enhance the edge detection. Furthermore, there are two more steps to improve the best quality for the input image: minutiae extraction and false minutiae removal. The minutiae extraction was carried out by applying ridge thinning algorithm which was to remove redundant pixels of ridges. As a result, the thinned ridges of the fingerprint image are marked with a unique ID so that further operation can be conducted. After the minutiae extraction step, the false minutiae removal was also necessary. The lack of the amount of ink and the cross link among the ridges could cause false minutiae that led to inaccuracy in fingerprint recognition process.

Pattern-based (or image-based) algorithms

Pattern based algorithms compare the basic fingerprint patterns (arch, whorl, and loop) between a previously stored template and a candidate fingerprint. This requires that the images can be aligned in the same orientation. To do this, the algorithm finds a central point in the fingerprint image and centers on that. In a pattern-based algorithm, the template contains the type, size, and orientation of patterns within the aligned fingerprint image. The candidate fingerprint image is graphically compared with the template to determine the degree to which they match.^[9]

In other species

Some other animals have evolved their own unique prints, especially those whose lifestyle involves climbing or grasping wet objects; these include many primates, such as gorillas and chimpanzees, Australian koalas and aquatic mammal species such as the North American fisher.^[130] According to one study, even with an electron microscope, it can be quite difficult to distinguish between the fingerprints of a koala and a human.^[131] Koalas' independent development of fingerprints is an example of convergent evolution.

In fiction

Mark Twain

Mark Twain's memoir Life on the Mississippi (1883), notable mainly for its account of the author's time on the river, also recounts parts of his later life, and includes tall tales and stories allegedly told to him. Among them is an involved, melodramatic account of a murder in which the killer is identified by a thumbprint.^[132] Twain's novel Pudd'nhead Wilson, published in 1893, includes a courtroom drama that turns on fingerprint identification.

Crime fiction

The use of fingerprints in crime fiction has, of course, kept pace with its use in real-life detection. Sir Arthur Conan Doyle wrote a short story about his celebrated sleuth Sherlock Holmes which features a fingerprint: "The Norwood Builder" is a 1903 short story set in 1894 and involves the discovery of a bloody fingerprint which helps Holmes to expose the real criminal and free his client.

The British detective writer R. Austin Freeman's first Thorndyke novel The Red Thumb-Mark was published in 1907 and features a bloody fingerprint left on a piece of paper together with a parcel of diamonds inside a safe-box. These become the center of a medico-legal investigation led by Dr. Thorndyke, who defends the accused whose fingerprint matches that on the paper, after the diamonds are stolen.

Film and television

On the television series Bonanza (1959–1973), the first episode with the ethnic Chinese character, Hop Sing, #316 The Mark of Guilt was about fingerprinting and its relationship to Chinese culture. Hop Sing uses his Oriental knowledge of "chops" (unique prints from fingers) to free Little Joe from a murder charge.

The movie Men in Black, a popular 1997 science fiction thriller, required Agent J, played by Will Smith, to remove his ten fingerprints by putting his hands on a metal ball, an action deemed necessary by the MIB agency to remove the identity of its agents.

In a 2009 science fiction movie starring Paul Giamatti, Cold Souls, a mule who is paid to smuggle souls across borders, wears latex fingerprints to frustrate airport security terminals. She can change her identity by changing her wig, and switching latex fingerprints from the privacy of a restroom, storing extra fingerprints in a ziploc bag, so she can assume an alias that is suitable to her undertaking.

Other reliable identifiers

Other forms of biometric identification utilizing a physical attribute that is nearly unique to humans include iris recognition, the tongue and DNA profiling, also known as genetic fingerprinting. Forensic dentistry has also been used as an identifier, but bite mark analysis is notable for being unreliable.^[133]

See also

References

Further reading

• Ashbaugh, David R. 1999. Quantitative-Qualitative Friction Ridge Analysis: An Introduction to Basic and Advanced Ridgeology. Boca Raton, Florida: CRC Press.


• Beavan, Colin. 2001. Fingerprints: The Origins of Crime Detection and the Murder Case that Launched Forensic Science. New York: Hyperion.


• Cowger, James C. 1992. Friction Ridge Skin: Comparison and Identification of Fingerprints. Boca Raton, Florida: CRC Press.


• Quinche, Nicolas, and Margot, Pierre. 2010. Coulier, Paul-Jean (1824–1890): A precursor in the history of fingermark detection and their potential use for identifying their source (1863). In Journal of Forensic Identification (California), 60 (2), March–April 2010, pp. 129–134.


• Scheibert, J, Leurent, S, Provost, A and Debregeas, G. 2009. The role of fingerprints in the coding of tactile information probed with a biomimetic sensor. Science 323: 1503–1506.

External links

This article's use of external links may not follow Wikipedia's policies or guidelines. Please improve this article by removing excessive or inappropriate external links, and converting useful links where appropriate into footnote references. (September 2018) (Learn how and when to remove this template message)

Media related to Fingerprinting at Wikimedia Commons

General

• Fingerprint Terminology


• 
  Fingerprint Sourcebook Multi-organization compendium on Fingerprints


• 
  The Fingerprint Society – Society for Fingerprint Experts


• International Association for Identification


• 
  Scientific Working Group on Friction Ridge Analysis, Study and Technology International Working Group on Fingerprints


• Interpol Fingerprint Research


• 
  The Science of Fingerprints FBI Publication


• FBI Fingerprint Guide


• 
  FBI Fingerprinting Video Lesson (4-sec QuickTime video of rolling a single inked finger)


• The History of Fingerprints


• Fingerprinting.com


• Fingerprint Processing Guide


• Fingerprint Articles at Crime & Clues


• Galton's Finger Prints
  


• Henry, Faulds, and Herschel's works on fingerprints


• 
  Extensive bibliography So. Calif. Assn. of Fingerprint Officers.

Errors and concerns

• Publications Critical of Fingerprint Identification


• Will West as fable


• 
  Do Fingerprints Lie? The New Yorker (2002)


• 
  Why Experts Make Errors, Itiel E. Dror, David Charlton, Journal of Forensic Identification


• 
  Surgeon jailed for removing fingerprints – Sydney Morning Herald (news article)

Science and statistics

• 
  Fingerprint research and evaluation at the U.S. National Institute of Standards and Technology.


• Fingerprint pattern distribution statistics