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. police force databases a city fingerprint identification office 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 of standards and technology (nist). for fingerprints recorded at 1000 ppi spatial resolution, law enforcement (including the fbi) uses jpeg 2000 instead of wsq. validity latent fingerprint analysis process 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. 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. the validity of forensic fingerprint evidence has been challenged by academics, judges and the media. in the united states fingerprint examiners have not developed uniform standards for the identification of an individual based on matching fingerprints. in some countries where fingerprints are also used in criminal investigations, fingerprint examiners are required to match a number of identification points before a match is accepted. in england 16 identification points are required and in france 12, to match two fingerprints and identify an individual. point-counting methods have been challenged by some fingerprint examiners because they focus solely on the location of particular characteristics in fingerprints that are to be matched. fingerprint examiners may also uphold the one dissimilarity doctrine, which holds that if there is one dissimilarity between two fingerprints, the fingerprints are not from the same finger. furthermore, academics have argued that the error rate in matching fingerprints has not been adequately studied and it has even been argued that fingerprint evidence has no secure statistical foundation. research has been conducted into whether experts can objectively focus on feature information in fingerprints without being misled by extraneous information, such as context. fingerprints can theoretically be forged and planted at crime scenes. professional certification fingerprinting was the basis upon which the first forensic professional organization was formed, the international association for identification (iai), in 1915. 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. other forensic disciplines have followed suit and established their own certification programs. history antiquity and the medieval period fingerprints have been found on ancient clay tablets, seals, and pottery. they have also been found on the walls of egyptian tombs and on minoan, greek, and chinese pottery. in ancient china officials authenticated government documents with their fingerprints. in about 200 bc fingerprints were used to sign written contracts in babylon. fingerprints from 3d-scans of cuneiform tablets are extracted using the gigamesh software framework. 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. although ancient peoples probably did not realize that fingerprints could uniquely identify individuals, 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. during china's qin dynasty, records have shown that officials took hand prints and foot prints as well as fingerprints as evidence from a crime scene. in 650 the chinese historian kia kung-yen remarked that fingerprints could be used as a means of authentication. in his jami al-tawarikh (universal history), the iranian physician rashid-al-din hamadani (1247–1318) refers to the chinese practice of identifying people via their fingerprints, commenting: "experience shows that no two individuals have fingers exactly alike." europe in the 17th and 18th centuries from the late 16th century onwards, european academics attempted to include fingerprints in scientific studies. but plausible conclusions could be established only from the mid-17th century onwards. in 1686 the professor of anatomy at the university of bologna marcello malpighi identified ridges, spirals and loops in fingerprints left on surfaces. in 1788 a german anatomist johann christoph andreas mayer was the first european to conclude that fingerprints were unique to each individual. in 1880 henry faulds suggested, based on his studies, that fingerprints are unique to a human. 19th century nine fingerprint patterns identified by jan evangelista purkyně fingerprints taken by william herschel 1859/60 fingerprints used instead of signatures on an indian legal document of 1952 in 1823 jan evangelista purkyně identified nine fingerprint patterns. the nine patterns include the tented arch, the loop, and the whorl, which in modern-day forensics are considered ridge details. in 1840, following the murder of lord william russell, a provincial doctor, robert blake overton, wrote to scotland yard suggesting checking for fingerprints. in 1853 the german anatomist georg von meissner (1829–1905) studied friction ridges, and in 1858 sir william james herschel initiated fingerprinting in india. in 1877 he first instituted the use of fingerprints on contracts and deeds to prevent the repudiation of signatures in hooghly near kolkata and he registered government pensioners' fingerprints to prevent the collection of money by relatives after a pensioner's death. in 1880 henry faulds, a scottish surgeon in a tokyo hospital, published his first paper on the usefulness of fingerprints for identification and proposed a method to record them with printing ink. returning to great britain in 1886, he offered the concept to the metropolitan police in london but it was dismissed at that time. up until the early 1890s police forces in the united states and on the european continent could not reliably identify criminals to track their criminal record. francis galton published a detailed statistical model of fingerprint analysis and identification in his 1892 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. in 1892 juan vucetich, an argentine chief police officer, created the first method of recording the fingerprints of individuals on file. in that same year, francisca rojas 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 álvarez, 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. this was the first known murder case to be solved using fingerprint analysis. in kolkata a fingerprint bureau was established in 1897, after the council of the governor general approved a committee report that fingerprints should be used for the classification of criminal records. the bureau employees azizul haque and hem chandra bose have been credited with the primary development of a fingerprint classification system eventually named after their supervisor, sir edward richard henry. 20th century the french scientist paul-jean coulier developed a method to transfer latent fingerprints on surfaces to paper using iodine fuming. it allowed the london scotland yard to start fingerprinting individuals and identify criminals using fingerprints in 1901. soon after, american police departments adopted the same method and fingerprint identification became a standard practice in 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. the identification of individuals through fingerprints for law enforcement has been considered essential in the united states since the beginning of the 20th century. body identification using fingerprints has also been valuable in the aftermath of natural disasters and anthropogenic hazards. 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. obim, formerly u.s. visit, holds the largest repository of biometric identifiers in the u.s. government at over 260 million individual identities. when it was deployed in 2004, this repository, known as the automated biometric identification system (ident), stored biometric data in the form of two-finger records. between 2005 and 2009, the dhs transitioned to a ten-print record standard in order to establish interoperability with iafis. female clerical employees of the los angeles police department being fingerprinted and photographed in 1928 in 1910, edmond locard established the first forensic lab in france. criminals may 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. in many jurisdictions the act of wearing gloves itself while committing a crime can be prosecuted as an inchoate offense. use of fingerprints in schools 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. 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. by 2007, it was estimated that 3,500 schools were using such systems. 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 bring only individual complaints against schools. 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. in march 2007, the uk 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". the liberal democrat home affairs spokesman nick clegg criticised "the determination to build a surveillance state behind the backs of the british people". the uk's junior education minister lord adonis defended the use of fingerprints by schools, to track school attendance as well as access to school meals and libraries, and reassured the house of lords that the children's fingerprints had been taken with the consent of the parents and would be destroyed once children left the school. an early day