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Forensic Fingerprinting

Akademische Arbeit 2017 7 Seiten

Jura - Strafprozessrecht, Kriminologie, Strafvollzug

Leseprobe

Table of Contents

Introduction

Ways to retrieve fingerprint evidence

Chemical composition of latent fingerprints

Reliability and Validity of Fingerprinting

Conclusion

References

Introduction

The world of forensic science has progressed vastly during the past decades, and it could not have thrived without the life-changing invention of fingerprinting. In fact, fingerprinting has long been considered as the most simple and unique way of recognizing an individual. The key purpose of fingerprinting in the field of forensics across the globe is to provide forensic identification and evidence. However, at the moment, the scientific reliability and validity of the method, used for identification in forensic fingerprinting, has been challenged.

Ways to retrieve fingerprint evidence

Retrieving fingerprint evidence often requires a calculated and vigilant search. As Geddes, (2010 pg. 10) states, the sort of fingerprint left in a scene typically determines the amount of resources such as the effort and time detectives must put in retrieving fingerprint evidence. To begin with, it is important to explore and understand the types of prints relevant in fingerprinting. According to Egli and Champion (2014 pg. 88), fingerprints occur in three different types made by a friction ridge print (pattern in a medium). These types include; patent or visible, plastic and latent. Patent prints are simple to identify because they can discern through the naked eye. This type of fingerprint happens when an individual has a substance on their fingers such as ink, blood, paint, or grease that leaves a noticeable mark on a surface.

Plastic Print, on the other hand, is relatively seen through a naked eye. As Galton (2012 pg. 39) asserts, these prints are easy to trace but are less common compared to the patent prints because they come about when a negative ridge imprint is replicated as a solid object from a soft material such as candle wax, butter, clay, or soap. Last but not the least, from the research conducted by Houck (2016 pg. 57), it is hard to perceive latent fingerprints. The reason behind this fact is that latent prints comprise wetness from sweat openings and constitute almost 95 percent of fluid with the remaining from amino acids and salt. Latent prints come about when an individual have a contact with a porous or nonporous surface.

The type of surface being examined or investigated for fingerprints repeatedly determine the method used to retrieve fingerprint evidence. These surfaces include; porous surfaces, non-porous surfaces, and human skin. The key techniques as discussed by Houck (2016 pg. 42) comprise; iodine fuming, powders, physical developer, superglue fuming, and ninhydrin.

Porous surfaces

In these surfaces, detectives regularly use chemical methods such as ninhydrin or iodine fuming to retrieve the evidence. Once one of these chemicals react with chemicals on the fingerprint residue, the print can be seen. Due to environmental concerns, iodine fuming occurs in a fuming chamber. The process involves melting solid crystal iodine which generates vapor that sticks to the greasy residue of print, creating a brown print Houck (2016 pg. 44). The key limitation of this technique is that the print disappears swiftly after the fuming occurs and hence, must be shot promptly. Ninhydrin is more ordinarily preferred than iodine fuming techniques due to its efficiency in locating a latent print (Cooper-Dunn et al., 2017). When the object containing the print is identified, it is sprayed with or dipped in a ninhydrin solution, which reacts with the molecules in the print deposit to generate a blue colored print.

However, ninhydrin techniques are very slow, in most cases taking a lot of time for the print to be seen. To solve this, the object comprising the print can be exposed to heat. The physical developer is also used to envisage the latent prints on porous surfaces such as wet paper. This technique involves a sequence of aqueous solutions. The object containing the print is initially immersed in a solution of maleic acid, then prewashed in the physical developer working solution. The object is finally dipped in water, dried and photographed. Geddes (2010 pg. 11) argues that the physical developer is a useful technique in acquiring results than other visualization methods.

Nonporous Surfaces

One of the key technique preferred in these surfaces includes powder technique. When the powder is spread on the surface, it reacts with the print residue, enabling the detective to see the print. The color of the powder should be different from that on the surface to enable enhanced visibility. For instance, a gray or white powder can be used while examining a black limestone countertop for prints. Another recognized technique for retrieving fingerprint evidence on the nonporous surfaces is superglue fuming. As it is done in a laboratory, the process takes place in an airtight tank, referred as a fuming chamber, to melt superglue which releases gasses that react with print residue, thereby making the print visible (Egli and Champod, 2014 pg. 90).

Superglue fuming can be conducted at any scene. Instead of using a chamber, a handheld wand that melts the superglue is used. Conducting superglue fuming at the scene can be important to save resources used in the course of the investigation. According to Ulery et al., 2011 pg. 7735), one of the limitation is that if the evidence is emitted for a long time interval, it can interfere with the print, making it useless. Also, an appropriate method for collecting and discovering latent prints is by dusting a nonporous surface with fingerprint powder. There is a wide range of powders that can be used for latent fingerprint recognition such as, white or black powder, fluorescent powders, gray aluminum powder, and magnetic powders (Egli and Champod, 2014 pg. 89). While using these powders, there is need to use a synthetic fiber brush with natural bristles. However, powders can contaminate the evidence and minimize the chance to apply other techniques that could make the print visible.

Human skin

The most difficult task is to locate and identify fingerprints left on the human skin. As Geddes (2010 pg. 10) points out, the first key difficulty is finding the print because the greasy remains left by fingers that make the fingerprint itself often exist on human skin. This makes it hard to distinguish between the print the surface. It is noted that after a print is left on the human skin, the greasy residue diffuses and is engrossed into the skin, making the print unclear. There is not a clear technique for retrieving fingerprint evidence on the human skin.

Chemical composition of latent fingerprints

Precisely, very little is known about the exact constituents of a latent fingerprint. This is because of the high number of parameters that impact the final composition. In fingerprinting, there are two chemical compositions: oily and clean prints (Cadd et al., 2015 pg. 222). Clean prints are deposited from newly clean hands, while oily prints are categorized as latent because of the deposition of sebum. While sebum is diffused from contact of hair, neck or face, eccrine glands deposit eccrine sweat from the palms of the hand. This enables the fingerprint to be identified. Even though these constituents certainly contribute to fingerprint residue, they do not offer either a wide-ranging list or recognize potential chemical activity over the time between visualization and deposition.

Reliability and Validity of Fingerprinting

Fingerprinting has been a dependable method used for proof of identity in the forensics field. As per the standards of friction ridge examination, fingerprinting is perceives as solid evidence for proving identity since early times. Langenburg et al. (2014 pg. 393) adds that this technique is reliable and valid as it is not possible to find two people who are perfectly alike. Fingerprint brings the concept of uniqueness, and each print is meant to one person only. In recent times, critiques have opposed the validity and reliability of fingerprinting. They argue that fingerprinting as an identification method needs to use probability for an outcome.

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Details

Seiten
7
Jahr
2017
ISBN (eBook)
9783668997196
Sprache
Englisch
Katalognummer
v494063
Institution / Hochschule
University of Birmingham
Note
3.6
Schlagworte
Fingerprinting

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Titel: Forensic Fingerprinting