fingerprint analysis

Abstract
This paper discusses the origins of fingerprinting and the usage of fingerprint analysis in the field of forensics. It traces the history of the practice from the 19th century on into the 20th and discusses the methods used to obtain fingerprints from a crime scene. It also examines some of the problems of fingerprint analysis and how it is not a foolproof manner of identification and never has been. It shows why fingerprint analysis should be used as a tool and not as an end-all-be-all means of identification for investigators conducting a criminal investigation. The numerous cases of mistaken identity based upon faulty forensics applied in the case of fingerprint analysis are sufficient to indicate the merit of this claim.
Keywords: fingerprint analysis, forensics fingerprinting, crime scene investigation
Introduction
The unique characteristics and contours of the fingerprint were first noted by 17th century anatomist Marcello Malpighi, who highlighted the spirals and ridges of the fingerprint and after whom the Malpighi layer is named. Some two hundred years later, fingerprinting as a way of identification was practiced by an English administrator in India. It was not long before fingerprinting became a primary way of identifying and databasing information on a person’s unique characteristics. Fingerprint analysis in the field of forensics was a staple of criminal justice by the middle of the 20th century, the FBI being in possession of 100 million fingerprint cards, which could be read by the Automated Fingerprint Identification System, which kept the files on digital drives (Hawthorne, 2008). This paper will provide background information on the history of fingerprint analysis, how the process is conducted today, and major controversies surrounding the practice in the field of forensics.
Historical Background
Fingerprint analysis has been a way of identifying individuals since the 19th century, when a British Administrator in India, Sir William Herschel, required civil contractors to provide both signatures and fingerprints (Herschel, 1916). By 1880, Dr. Henry Faulds had published an article on fingerprinting in the journal Nature (Reid, 2003). Two years later in France, Alphonse Bertillion devised the Bertillion System of classifying identification measurements of persons based on their body measurements, such as height and length—a system that would be used for classification purposes until fingerprinting would prove a better option. In 1891, the system of fingerprinting criminals was put into practice in Argentina, and in 1892, Sir Francis Galton published a book in England on how fingerprints are unique to each and every person (a claim that has never been substantially verified by scholarship). In 1901, Sir Edward Henry, in India, instituted the world’s first systematic classification of fingerprints, which would eventually be adopted by the United Kingdom and dispersed through the rest of the world. In 1903, the need for fingerprinting as a formal classification of identification was seen when at Leavenworth prison, two inmates by the same name and same Bertillion measurements were incarcerated. Fingerprint identification was seen as the best method of distinguishing individuals—and two years later, the U.S. military was using fingerprints of soldiers for that exact purpose. Law enforcement agencies soon followed, and the first fingerprint card was put in use in 1908 in the U.S. Zabell (2005) has, however, noted that while reliability of fingerprint identification and verification is attainable in fingerprint analysis, validity is still a concept that the field has yet to attain with consistency.
Process
As skin produces an oily residue that can be left behind on physical surfaces, the imprint of fingerprints can essentially be left behind on any solid surface as well. However, prints can also be left behind when any residue, such as blood, ink, or dirt is on the fingers when they come into contact with a surface. Fingerprint analysts can retrieve fingerprints from soft surfaces, such as soap or wax; they can retrieve them from flat, hard surfaces, such as glass, wood, walls, and so on—whether the prints are patent or latent (visible or invisible to the eye). Latent prints can be retrieved from a range of surfaces, from paper and cloth to metal and plastic. To recover latent prints, fingerprint powder is required, and the analyst must dust for prints. The dust adheres to the oils deposited by the fingers when they come into contact with a surface, thus rendering the print patent, which allows it then to be copied for databasing and indexing to see if a match can be made and an identity of the owner of the prints distinguished (NFSTC, 2013).
For patent prints, the collection method is photographic. High resolution photography in combination with a forensic measurement scale is used. Sometimes lighting and dye may be used to enhance the patentability of the print, but often this is not required. Latent prints are either dusted for or sought using cyanoacrylate vapors, which cling to the oil residue of the prints on any non-porous surfaces, so as not to disturb the crime scene. If discovered, they are photographed and lifted using adhesive tape.
Light sources can also be used to discover fingerprints and this method has become increasingly common in an effort to prevent a crime scene from being disturbed. Blue lights with orange filters are one way for the forensics team to identify latent prints on solid surfaces (NFSTC, 2013). The forensics team is not limited to any one method, so if one is not suitable, there are a variety of others to employ.
For porous surfaces, prints are obtained using chemicals, such as ninhydrin, which can be used as a reactant when coming into contact with amino acids and inorganic salts left behind by fingers when they touch a porous surface. The chemical turns the prints purple, and that allows them then to be photographed. Prints can also be obtained from skin or clothing: these methods include the use of Amido Black or vacuum metal deposition.
Once the prints are found, they are uploaded to a computer database for indexing and matching if possible. Local, state and national databases exist for helping investigators determine if the prints belong to anyone whose prints are already on file. Today, algorithms are used to assign values to any matches that are made based on similarity of print type. Prior to computerization, prints were manually filed and classified according to ridge patterns, which were classified with values, too. These classifications include the arch, loop, whorl, and tented arch structure, according to the Henry (1900) classification system.
Controversy and Limitations
Like all forensics methodologies, there is a high degree of subjectivity to the science of fingerprint analysis and, as Zabell (2005) states, “recent years have seen an increasing number of challenges to fingerprint evidence” (p. 143). In spite of fingerprint analysis serving as the “gold standard” of identification in the field of criminal forensics, the use of DNA evidence has contributed substantially to the conversation on whether or not fingerprint analysis is as justifiable in a modern crime lab as it was one hundred years ago before DNA technology allowed for greater access to forensics data.
There are a number of cases where the validity of fingerprint analysis has come into question. Brandon Mayfield, an Oregon lawyer, was arrested by the FBI in 2004 after his fingerprints matched one taken from the scene of a Madrid bombing that killed nearly 200 people. Mayfield was detained for more than two weeks based on the fingerprint analysis before being freed by Spanish authorities after the actual culprits of the terrorist act were apprehended. The FBI issued an apology to the American and pledged to undertake a thorough review of its fingerprint analysis processes (Innocence Project, 2018).
The “gold standard” label that Zabell (2005) notes has so often been applied to fingerprint analysis is no doubt based on the fact that fingerprint analysis has assisted in a great many crime scene investigations. But even the National Academy of Sciences (2009) has issued a warning about the extent to which one should attach validity to the field of fingerprinting analysis, stating:
Claims that these analyses have zero-error rates are not plausible; uniqueness does not guarantee that two individuals' prints are always sufficiently different that they could not be confused, for example.  Studies should accumulate data on how much a person's fingerprints vary from impression to impression, as well as the degree to which fingerprints vary across a population.  With this kind of research, examiners could begin to attach confidence limits to conclusions about whether a print is linked to a particular person.
This is not to suggest that the National Academy of Sciences is urging forensics teams to dispense with fingerprint analysis—on the contrary, the Academy finds the field to have its uses, but it seeks to promote temperance with regard to the application of its usage. Rather than relying on fingerprint analysis to determine guilt or even identity, researchers and investigators should use it only as a tool to help include or exclude a person from a fuller investigation. The Academy goes on to note that “disciplines that are too imprecise to identify an individual may still be able to provide accurate and useful information to help narrow the pool of possible suspects, weapons, or other sources…  For example, the committee found no evidence that microscopic hair analysis can reliably associate a hair with a specific individual, but noted that the technique may provide information that either includes or excludes a subpopulation.” In other words, evidence obtained through forensics is not foolproof and must not be taken as 100% valid. It should be used rather to qualify inclusion or exclusion, and that is all.
As Zabell (2005) points out, prints can be mismatched and misidentified, resulting in innocent persons being incarcerated based on faulty forensics analysis. This is lamentable and to be avoided, according to the researcher, who cites the case of Richard Jackson, whose prints were said to match the latent prints taken from a crime scene, though photographic evidence clearly indicates the prints are in no wise compatible. Zabell (2005) highlights the case of Stephan Cowans, accused of assaulting an officer, convicted and sentenced to prison after a fingerprint examiner was used in the court of law to verify that the prints taken at the scene of the crime belonged indeed to Mr. Cowans. After six years behind bars, Cowans won an appeal to obtain DNA evidence from the scene of the crime, which indicated that the DNA taken from the scene belonged to another suspect and not to Cowans. The conviction was overturned when it was determined that a mistake had been made with respect to the fingerprint evidence: there was no match between Cowans’ prints and the prints lifted from the scene of the crime. Cowans was exonerated—but only after spending more than a decade in prison for a crime he did not commit. Faulty fingerprint analysis was used to convict him. DNA evidence was used to exonerate him—at which point it became clear that a better examination of the fingerprint evidence showed the truth.
This goes to show that no matter what type of evidence is used in forensics, there will always be the risk of eager prosecutors using faulty forensics to land a conviction. The problem, here, is not so much in the forensics process as in the problem of who is entrusted with completing that process and how the process is manipulated to convict a person. In any field of forensics there is room for abuses, and fingerprint analysis is no exception. In the future, individuals in the field may use computerized, algorithmic searches to help find matches—but even this is no guarantee that a similarity is meaningful. As the National Academy of Sciences warns, fingerprint analysis is a tool that investigators should use—not to convict—but rather to help in terms of who or who may not be included as a suspect.
Conclusion
Fingerprint analysis goes as far back in time as the 17th century, when the ridges of the fingerprint were first examined by an anatomist in Italy. Since then, the fingerprint has become a source of particular appeal for forensics analysts: the appeal is based on the understanding that no two fingerprints are alike. Fingerprint analysis has been helpful in many cases over the decades since its inception in law enforcement in the 20th century. However, it has never been a foolproof practice, nor does it have a 100% pass rate. There have been many instances in which the fingerprints lifted from one scene were used to convict a man who was not there. There have been cases where prints that seemed to match were used to imprison persons who could not have been said otherwise to have any reason for being suspected. Fingerprinting analysis is based on the match of small ridges and whorls, and the difficulty often lies in the complexity of the ridges and whorls in the human finger and in the difficulty of turning up a fine print for analysis. The better the print, the more accurate the reading and matching can be—but in the real world, turning up fine prints, even with all the technological power that is available to investigators today, is not always as easily done as said. For that reason, caution is advised by the National Academy of Sciences.
References
Hawthorne, M. (2008). Fingerprints: Analysis and understanding. Boca Raton, FL: CRC
Press.
Henry, Edward R., Sir (1900). Classification and Uses of Finger Prints. London: George
Rutledge & Sons, Ltd.
Herschel, W. J. (1916). The Origin of Finger-Printing. Oxford University Press.
Innocence Project. (2018). Fingerprint analysis. Retrieved from
https://californiainnocenceproject.org/issues-we-face/fingerprint-analysis/
National Academy of Sciences. (2009). Badly fragmented' forensic science system needs
overhaul; evidence to support reliability of many techniques is lacking. Retrieved from http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=12589
NFSTC. (2013). Fingerprint analysis. Retrieved from
http://www.forensicsciencesimplified.org/prints/how.html
Reid, D. L. (2003). Dr. Henry Faulds – Beith Commemorative Society. Journal of
Forensic Identification, 53 (2).
Zabell, S. L. (2005). Fingerprint evidence. Journal of Law and Policy (Brooklyn College
Law School), 143–77.