The Science of Fingerprints and Their Characteristics
Introduction
In their daily lives, people constantly touch objects: a cup of coffee, a bunch of keys, and a cell phone. Every time they do, they most likely leave a unique signature behind in one’s fingerprints. According to Forensic Science Simplified (n.d.), fingerprint analysis has been employed in the identification of suspects and the solution of crimes for over 100 years and remains an exceptionally beneficial tool for law enforcement. One of the most important uses of fingerprints is to assist investigators in linking one crime scene to another featuring the same person. The determination of prints is usually conducted with the employment of the ACE-V method and identification of a print’s class and individual characteristics, both of which are essential to obtaining reliable results.
Fingerprints are classified into three categories depending on the type of surface they are found on and their visibility. Those on soft surfaces, for instance, wet paint, wax, and soap, are often three-dimensional plastic prints. Hard surface prints are classified into patent or latent – or, in other words, visible or invisible. Patent prints form when any substance – dirt, paint, blood, and so on – is transported to a surface from a finger. Latent prints form when body oils or sweat land on a surface. One often needs to turn to additional tools to detect latent prints, which are not visible easily. As a rule, the smoother and less porous a surface, the better the chance that a latent print present is found and developed.
The ACE-V Method
Fingerprint analysis is generally conducted by law enforcement agencies or crime laboratories. Fingerprint examination involves inspecting the quality and quantity of information gathered to find the correlation between the unknown fingerprint from the crime scene and the known fingerprints. For the examination, experts on fingerprints use a loupe, a small magnifier, to view minutiae, a print’s minute details, and a pointer named a ridge counter to count the friction ridges (Forensic Science Simplified, n.d.). The method known as the ACE-V, which stands for analysis, comparison, evaluation, and verification, is employed to achieve a determination on a print.
The analysis is the evaluation of a print to determine whether it can be used for comparison. If an examiner concludes that it is not suitable due to insufficient quality or quantity of features, the examination ends, and a print is reported to be unsuitable. If it is suitable, the features that will be used in comparison and their tolerances – that is, the number of changes that will be accepted – are indicated. The analysis might reveal specific physical features such as scars, deltas, and creases that help specify where a comparison is to begin.
Comparison is performed by an analyst who looks at the known and suspected prints side by side. An analyst’s role is to compare minutiae locations and characteristics to evidentiate if they match. As per Forensic Science Simplified (n.d.), known fingerprints are usually obtained from people directly or from searching fingerprint databases, for example, the Integrated Automated Fingerprint Identification System. It is the world’s largest fingerprint database and holds tens of millions of print records from criminals, government employees, military personnel, and civil servants.
The next step is evaluation, which is when an expert ultimately decides whether the fingerprints are of the same source (identification or individualization), different sources (exclusion), or it is inconclusive. The latter might be due to poor sample quality, lack of comparable areas, or an inadequate number of corresponding features to come to definite conclusions. Finally, there is verification, and that is when another examiner separately analyzes, compares, and evaluates the fingerprints to confirm or disprove the previous expert’s verdict.
Fingerprint Characteristics
As it has been mentioned above, once the fingerprint is obtained, analysis can begin. During the analysis phase, experts determine whether there is enough information in the print to identify it. This involves the determination of class and individual characteristics for the unknown print. According to SWGFAST (n.d.), class characteristics are the characteristics that reduce the print to a group but not to a person. Three class characteristics of fingerprints are loops, whorls, and arches. Loops are the prints re-curving back on themselves to form a loop shape, and they are the most common prints, accounting for 60-65% of pattern types (SWGFAST, n.d.). Whorls form circular patterns and look like tiny whirlpools, and they comprise 30-35% of pattern types (SWGFAST, n.d.). Finally, SWGFAST (n.d.) notes that arches amount to only 5% of pattern types, which makes them the rare fingerprint type. Arches are formed by ridges coming in on the print’s one side, going up, and coming out from the other side.
Individual characteristics are the characteristics that are unique to each person. These are tiny humps that emerge within the friction ridges that are called Galton’s details. The most common types of these details are bifurcations, islands, and ridge endings. Initial comparisons are made with the employment of class characteristics, which helps analysts determine whether a known fingerprint needs to be further analyzed. For the process of print matching, an expert looks at the minutiae to identify particular spots on a suspect print with the data in a known print. For instance, an expert that compares crime scene prints to those on file first collects known ones with identical class characteristics. After that, they use a loupe and compare the prints side by side for the identification of minutiae information that matches. In the case of enough detail correlating, the fingerprints are considered to belong to the same person.
Print Analysis
When it comes to the print titled “Young Print”, this fingerprint seems to be one of a high enough quality to be used to find a match based on what can be seen in the picture. According to Peterson et al. (2009), ridge bifurcations are single ridges dividing into two separate bridges. Islands are single small ridges inside short ridges or ridge endings not connected to other ridges (Peterson et al., 2009). Moreover, as per Peterson et al. (2009), ridge endings are simply the ends of ridges. There are a few bifurcations closer to the middle of the fingerprint and a couple of islands closer to its bottom. In terms of ridge endings, there is a prominent one on the left side of the print. This information should be sufficient to conduct the ACE-V procedure with this print.
Conclusion
In conclusion, fingerprint analysis is an extremely useful law enforcement tool that assists in solving crimes. The determination of a print is reached with the employment of the ACE-V method, each stage of which plays an important function in print identification. In addition, the division of fingerprint characteristics into class and individual ones helps experts in the step-by-step comparison of different prints. These procedures are instrumental in tracking suspects, finding criminals, and, as a consequence, potentially administrating justice.
References
Forensic Science Simplified. (n.d.). A simplified guide to fingerprint analysis.
Peterson, P. E., Dreyfus, C. B., Gische, M. R., Hollars, M., Roberts, M. A., Ruth, R. M., Webster, H. M., & Soltis, G. L. (2009). Latent prints: A perspective on the state of the science. Forensic Science Communications, 11(4).
Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST). (n.d.). Document #8 Standard for the Documentation of Analysis, Comparison, Evaluation, and Verification (ACE-V) (Latent).