Fingerprints: Principle of Identification Used by Criminal Investigators

As an elementary principle of identification used by criminal investigators, a fingerprint can be defined as a sense of chance impression found on the tips of the human finger by the fraction ridges and tends to follow a pattern of definite design (ONeil 929). Fingerprinting is a fundamental tool in criminal law, particularly against crime. Every individual's fingerprints contain hundreds of tiny patterns and shapes that are unique. Every police department that integrates fingerprint analysis technology usually has thousands if not hundreds of different fingerprints on their file database. Consequently, to catch a criminal, these experts have to match or run a single print from the scene of the crime with one of those in the database. Therefore, without a computer, it can be a very tedious task if not an impossible one. In this light, this paper will briefly discuss fingerprints; where they can be found, the three types of fingerprint patterns, and how they are collected and analyzed.

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Where Fingerprints can be found

As earlier mentioned, fingerprints come from the tips of the human finger, and they are unique to every person. They can be found on any solid surface. According to Forensic Science Simplified, fingerprints that are found on soft surfaces such as wet paint or soap can be termed as plastic prints. On the other hand, those located on hard surfaces such as glass or paper are visible prints. Additionally, latent prints can be found when sweat and the bodys natural oils are deposited to another surface. Conversely, latent prints are not easily visible by forensic investigators and they often use chemical reagents and fingerprint powders or light sources to investigate. The less porous and smoother a surface is, the greater the potential that the latent prints can be developed or found by the investigator.

The Three Main Types of Fingerprint Patterns

ONeill indicates that in the U.S, the Henry system of fingerprint classification is used and all fingerprint patterns are divisible into four main types: loops, Arches, and whorls (929). Loops patterns are those whereby the fraction ridges enter from the sides of the finger and re-curves as it ends the same way as it entered. Loops patterns occur in about 70% of the fingerprints. Arches are those whereby the fraction ridges run across the tips of the finger from one side to another without re-curving. They are found in almost 5% of the fingerprints encountered. Finally, the whorls patterns have been found in about 25% of the fingerprints encountered. They are patterns whereby the ridges make a full circuit on the fingertips, forming a spiral or ring shape. Note that whorls and loops are very common as compared to arches. On a lighter note, many hand-readers often associate loops people to be easy going while whorls are highly focused individuals.

Figure1: the three basic pattern types (ONeill).

How Fingerprints are Collected and Analyzed

The most common method for collecting and discovering latent fingerprints is by dusting nonporous or smooth surfaces with fingerprint powder such as black magnetic and black granular. If a print appears, it is photographed and collected using clear tape. Nonetheless, when collecting the fingerprints, the powders can contaminate the evidence hence investigators often use techniques to examine such as cyanoacrylate and alternate light source. On the other hand, patent prints are collected using photography. Such prints are photographed in high resolutions with forensic technology. Criminologists or forensic investigators enhance the image quality by alternate light source and chemicals or dyes during the photography (Forensic Science Simplified). For instance, the image below shows a paper treated with chemical reagents to expose fingerprints.

Image 2: revealing latent prints with ninhydrin reagent (Forensic Science Simplified).

To conclude, after collecting the prints, criminal investigators use computerized systems to run the prints and search through fingerprint databases for possible matches. Based on the computer algorithm, the examiners then review the results and make a final verdict. Therefore, fingerprints analysis is a joint approach done by police officers, technicians, and forensic scientists. The analysis is performed in crime laboratories by law enforcers. It involves the examiner conducting an investigation into the quality of the prints while using a small magnifier called the loupe. Also, a ridge counter which is the pointer is used to count the ridges found on the fingerprints. Image 3 below shows how examiners use the loupe and ridge counter to analyze fingerprints information during forensic investigations.

Image 3: fingerprint analysis using loupe and ridge counter (Forensic Science Simplified).

Works Cited

Forensic Science Simplified,. "Fingerprint Analysis: How It'S Done." Forensicsciencesimplified.org. N.p., 2013. Web. 8 Oct. 2016.

O'Neill, M. Edwin. "Fingerprints in Criminal Investigation." Journal of Criminal Law and Criminology (1931-1951) 30.6 (1940): 929. Web.