Eleanor Finch
Fingerprints are considered a form of individual evidence as the ridge arrangement on every finger of every human is unique and remains unchanged with growth or age. The basic fingerprint patterns are whorl, arch, and loop. The combination of details in the shapes and positions of ridges in fingerprints, also called ridge characteristics, make each unique. The validity of forensic fingerprint evidence has been challenged by academics, judges, and the media, with arguments that the error rate in matching fingerprints has not been adequately studied.
| Characteristics | Values |
|---|---|
| Basic fingerprint patterns | Whorl, arch, and loop |
| Minutia | Unique characteristics in a fingerprint that individualize it |
| Ridge count | A commonly used metric of fingerprint pattern size |
| Ridge characteristics | The combination of details in the shapes and positions of ridges in fingerprints that make each unique |
| Ridge structure | Reproduce in sweat, oily secretions, or other substances naturally present on the culprit's fingers |
| Ridge arrangement | Unique to every finger of every human being and does not alter with growth or age |
| Identification points | In England, 16 identification points are required to match two fingerprints and identify an individual; in France, 12 are required |
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What You'll Learn
Fingerprints are unique and remain unchanged
The overall pattern of ridges and valleys, as well as the logical ridge discontinuities known as minutiae, contribute to the uniqueness of a fingerprint. In the 2000s, minutiae features were considered the most discriminating and reliable feature of a fingerprint, and they became the most common basis for automated fingerprint verification. The recovery of partial fingerprints from a crime scene is an important method of forensic science, as fingerprints can be used to identify individuals who wish to conceal their identity or who are incapacitated or deceased.
Fingerprints are considered a form of individual evidence, and they can be used to identify suspected criminals as well as victims of crime. The process of fingerprint identification involves capturing the graphical ridge and valley patterns, which can then be compared to known recordings of friction ridge impressions. Factors such as pliability of the skin, deposition pressure, surface material, and roughness can cause a latent print to appear differently from any known recording, so extensive training is required for fingerprint examiners.
While fingerprints are generally considered unique and permanent, their use as evidence has been challenged. Academics have argued that the error rate in matching fingerprints has not been adequately studied and that there is no secure statistical foundation for fingerprint evidence. Research has also been conducted into whether experts can focus on feature information in fingerprints without being influenced by extraneous information.
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Minutiae: the combination of ridge shapes and positions
Minutiae are the small, unique characteristics of a fingerprint that individualise it. They are the combination of details in the shapes and positions of ridges, also called ridge characteristics. The ridge structure is formed by friction ridges on the fingers, leaving an impression in substances such as sweat, oils, blood, ink, or other materials naturally present on the fingers.
The ridges on every finger of every human being are unique and remain unchanged with growth or age. Even injuries such as superficial burns, abrasions, or cuts do not alter the ridge structure. Minutiae are, therefore, a reliable form of biometric identification.
The basic fingerprint patterns of whorl, arch, and loop are considered class evidence. However, the individual ridge characteristics within these patterns are unique to each person. The Federal Bureau of Investigation (FBI) in the United States recognizes eight different types of patterns: radial loop, ulnar loop, double loop, central pocket loop, plain arch, tented arch, plain whorl, and accidental. Loops constitute about 65% of total fingerprint patterns, whorls make up about 30%, and arches and tented arches account for the remaining 5%.
The identification of an individual based on matching fingerprints can be challenging due to the lack of standardized methods and the subjective nature of analysis. The number of identification points required to match fingerprints varies across countries. For example, 16 points of identification are required in England, while 12 points are needed in France. The validity of forensic fingerprint evidence has been questioned by some academics, judges, and media outlets, who argue that the error rate in matching fingerprints has not been adequately studied.
Despite these challenges, fingerprints are considered a reliable form of individual evidence. Minutiae, or the unique combination of ridge shapes and positions, play a crucial role in differentiating one person's fingerprint from another.
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Ridge counts: influenced by multiple additive genes
Fingerprints are considered a form of individual evidence. They are formed deep within the dermis layer of the skin and are unique to each individual. The basic fingerprint patterns are the whorl, arch, and loop. However, it is the minutiae—the unique characteristics in a fingerprint—that truly individualize it. These include the shapes and positions of ridges, which are influenced by multiple additive genes.
Ridges in biology are regions of the genome with increased gene expression. They are characterized by high gene density, short introns, high SINE repeat density, and low LINE repeat density. The high gene expression in these regions is due to the clustering of functionally related genes, which share a common promoter unit.
The number of ridges on a fingerprint is influenced by multiple additive genes. Ridge regression is a statistical technique used in quantitative genetics to estimate the additive effects of genetic variants. It allows for the simultaneous estimation of all additive effects, reflecting the idea that all variants contribute in a small way. This method has been applied in plant breeding populations to predict genotypic values with DNA markers.
The use of ridge regression helps overcome the issue of over-fitting in machine learning. Over-fitting occurs when a model becomes overspecialized in the dataset used for parameter estimation and cannot generalize to new data. Ridge regression acts as a regularization technique, reducing the complexity of the model to prevent over-fitting.
In the context of genome-wide prediction, ridge regression provides an alternative to Bayesian approaches, particularly when computational efficiency or accurate effect estimation is a priority. It has been applied in plant breeding to overcome the limitations of the Best Linear Unbiased Prediction (BLUP) approach, which assumes that all genes contribute to a trait, rather than a subset of genes.
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Friction ridge impressions: affected by the surface environment
Fingerprints are considered a form of individual evidence. Friction ridge impressions are a type of fingerprint that includes latent, patent, and plastic prints. These impressions are left on items or at crime scenes through the transfer of materials such as blood, dirt, dust, paint, sweat, oils, and other residues. The surface environment can affect the development and preservation of these friction ridge impressions.
Latent prints are unintentional reproductions of friction ridge skin left on items by the transfer of residue. They often require development techniques to be visualized, such as superglue fuming, black powder, fluorescent dye staining, or ninhydrin. The type of powder used to dust prints may vary depending on weather conditions.
Patent prints, on the other hand, are visible reproductions of friction ridge skin left behind by the transfer of materials such as blood, dirt, dust, or paint. While they may be visible to the naked eye, they can also benefit from development techniques. Plastic prints are three-dimensional reproductions left in pliable surfaces like clay and are typically photographed and enhanced with black powder.
The persistence of friction ridge impressions refers to the reliable representation of three-dimensional skin details in two dimensions. This persistence acknowledges the distortions and dissimilarities that can arise due to factors such as matrix, substrate, and applied pressure. The transfer fidelity, or the degree to which the impression accurately captures the fingerprint details, can be limited by the variability in skin conditions and ambient environment.
Photography is often used to capture friction ridge impressions and can serve as a ground truth reference for comparison with other methods. However, photography also has limitations in terms of quality and clarity due to the technique, skill of the operator, and the condition of the friction ridge skin. Other capture methods include ink, holographic imaging, and live scans, each with their own advantages and limitations. Overall, the surface environment and capture techniques play a crucial role in the development, preservation, and analysis of friction ridge impressions.
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Fingerprint evidence: challenged due to lack of standardisation
Fingerprints are considered a form of individual evidence. The uniqueness of fingerprints is attributed to the minutiae—the unique characteristics or ridge patterns that individualize a fingerprint.
Despite being regarded as one of the most reliable tools for convicting criminal suspects, fingerprint evidence has faced increasing scrutiny due to the lack of standardisation in the identification process. This has led to concerns about the accuracy and reliability of fingerprint evidence in criminal trials.
One of the primary challenges is the subjectivity of analysis and the potential for examiner bias. Fingerprint examiners often need to make subjective judgments when comparing partial or smudged prints, which can result in inconsistencies between different examiners analysing the same print. The skill and experience of the examiner significantly impact the reliability of the analysis. Additionally, the potential for bias can influence an examiner's decision, especially when they have access to contextual information about the case.
The quality of crime scene prints can also vary due to environmental factors such as dirt, moisture, or grease, which can affect the clarity and completeness of the fingerprint. Crime scene prints may be incomplete, smudged, or contaminated, further complicating accurate identification.
Furthermore, there is no universally agreed-upon standard for the number of "points of comparison" required to make a positive identification. This lack of standardised criteria for identification makes it difficult to ensure consistent and accurate results across different examiners and laboratories.
The challenges associated with fingerprint evidence have led to calls for greater scepticism in its use as definitive forensic evidence. While fingerprinting can be a powerful tool for identification, it should be carefully evaluated and presented alongside other supporting evidence to ensure the fairness and accuracy of criminal trials.
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Frequently asked questions
Fingerprints are impressions made by the papillary ridges on the ends of the fingers and thumbs.
The ridge arrangement on every finger of every human being is unique and does not alter with growth or age.
The basic fingerprint patterns are whorl, arch, and loop.
Minutiae are the unique characteristics in a fingerprint that individualize it.
The number of identification points required to match fingerprints varies by country. For example, 16 points are required in England, while 12 points are required in France.
