Latent Prints Research Articles

Organic fluorophores in developing latent fingerprints: an up-to-date review

AbstractFingerprints have been established as legitimate and critical forensic science evidence for identifying criminals beginning as early as the twentieth century. This article details the different types of fingerprints, the broad range of surfaces, and various development techniques available for on-site latent fingerprint collection, with fingerprint fidelity being of prime significance. Fluorescent imaging of latent finger-marks benefits from enhanced sensitivity, selectivity, and reduced reliance on instruments. The review focuses on the topical developments reported on small-molecule organic fluorophores which could be used to develop latent prints through powder, solution, and fuming approaches. These inexpensive luminophores extend wide emission profiles that span the visible spectrum to visualize the latent prints with exceptional resolution, free from any interference originating from the background surface. Further, the critical challenges and prospective scope for future research developments to improve the detection of latent fingerprints using small-molecule fluorophores are also discussed. Graphical abstract

The other side of the paper as the evidence: impacts of fingermark development reagents on fingermark development and cocaine amount in cocaine-impregnated paper.

Despite various preventative measures, cocaine smuggling is still a major problem worldwide. A recent method of smuggling is the transportation of cocaine with various chemicals or with impregnated materials such as cloth and paper. This study aims to examine the change in the amount of cocaine on the paper surface and attempts to decide the best fingermark development method in the case of smuggling trafficking in the form of impregnated paper with the least effect on the cocaine concentration on the paper. The papers (n = 6 + 1) were prepared for each fingermark development method, including a blank paper, were dipped into a working solution prepared by dissolving 0.38mg cocaine in 500 mL methanol. Fingermarks were developed by applying various chemicals, including Iodine vapor, 1,2-Indandione, DFO (1,8-diazafluoren-9-one), ThermaNin, 5-MTN (5-methylthioninhydrin), and silver nitrate chemicals and Ninhydrin, which is the most commonly used reagent for visualizing latent prints, particularly on paper surfaces. Also, the natural fingermarks of four different donors, two women and two men between 20 and 50 years of age, were used to compare with the presence of cocaine. Different from others, this study examined the application of DFO and 1,2-Indandione as alternatives to other chemicals and revealed that it is possible to identify cocaine using these methods. The order of success was Ninhydrin > DFO > 1,2-Indandione > ThermaNin > Iodine vapor = 5-MTN. To the best of our knowledge, the current study is the first to investigate fingermark identification methods along with the amounts of cocaine on cocaine-impregnated papers.

A Comprehensive Review of Small Particle Reagent Efficacy in Developing Latent Fingerprints Immersed in Water: An Empirical Analysis

A latent fingerprint is a shred of inevitable evidence left on a scene of the crime by the offender. Being aware of fingerprints, offenders tend to deteriorate all possible pieces of evidence by different methods that include burning, immersing the evidence in water, and many more. Water-immersed latent fingerprints are still viable for the development process due to the presence of water-insoluble components (Lipids, oils, etc.) in the latent fingerprint. Different methods have been tested for the imaging of water-immersed latent fingerprints among which Small Particle Reagent (SPR) was found to be the most efficient by many researchers. This method involves the application of fine particles suspended in a reagent based liquid medium onto the surface containing latent prints immersed in water, resulting in the development of highly detailed fingerprint impressions. The reagent comprised of hydrophobic head and hydrophilic tails that adhere to latent fingerprint and suspended particle respectively and thus act as a junction among them. The diverse composition of Small Particle Reagent, various surfaces for taking impressions of latent fingerprint (followed by immersing in water), the Shelf life of SPR, immersion time of latent fingerprint, and various immersion medium studied by researchers has been reviewed in this paper. The maximum shelf life of SPR reported by a researcher is 6 months and the maximum immersion time is 45 days. Furthermore, the need for green synthesis of SPR is emphasized due to its toxicity caused by long-term exposure.

End-to-end latent fingerprint enhancement using multi-scale Generative Adversarial Network

Latent fingerprint enhancement is paramount as it dramatically influences matching accuracy. This process is often challenging due to varying structured noise and background patterns. The prints may be of arbitrary sizes and scales with a high degree of occlusion. There is a need for creating an end-to-end system that handles different conditions reliably to streamline this often lengthy and tricky process. In this work, we propose a Generative Adversarial Network (GAN) based architecture that effectively captures multi-scale context using Atrous Spatial Pyramid Pooling (ASPP). We have trained the network on a synthetically generated dataset, carefully designed to represent real-world latent prints. By avoiding the reconstruction of spurious ridges and only enhancing valid ridges, we avoid the generation of false minutiae, leading to better matching performance. We obtained state-of-the-art results in Sensor to Latent matching using the IIITD MOLF and Latent to Latent Matching using IIITD Latent datasets.

The effects and benefits of a latent print AFIS deferral policy

Forensic laboratories in the United States had an estimated backlog of 570,100 requests for all forensic services at the end of 2014. Latent print requests represented approximately 12% of that total backlog [1, NIJ 2019]. With ever-increasing demands and backlogs, a review of laboratory or section practices becomes vital to operations. Work process and business practice changes can increase efficiencies and result in the reduction of casework backlogs and turnaround times. The automated fingerprint identification system (AFIS) deferral policy implemented by the Latent Print Comparative Section (LPCS) of the Phoenix Police Department Laboratory Services Bureau (PPD LSB) was employed to address the latent print backlog. Five years of multiple AFIS request types were analyzed to demonstrate the positive effects and benefits of such policies, including a 26.32% decrease in turnaround time over the data collection and analysis period and a 90.96% reduction in backlogged requests for one year.

Forensic Fingerprint Analysis

Fingerprint evidence found at crime scenes provides vital impressions left when these skin secretions touch surfaces clues in serial criminal investigations. A fingerprint identification system employing deep machine learning and Convolutional Neural Networks (CNNs) could automate the analysis process. Images obtained from various physical and chemical crime scene investiga2tion techniques are entered into the database. However, partial latent prints lifted from scenes are often difficult to classify. The system operates in three phases: preprocessing fingerprint images, feature extraction, and matching. Preprocessing enhances image quality before feature extraction identifies distinctive minutiae points - ridge endings and bifurcations. False minutiae removal further refines the data. The preprocessed fingerprint data serves as input to train and test the CNN model. As the system persist due to the immutable individuality of fingerprint ridge arrangements [5]. While criminals attempt concealment, fingerprint traces stubbornly remain where other evidence would dissipate [6]. Without these durable biometric markers, crime scenes would often lack the critical traces needed to connect acts to perpetrators [7]. Latent prints lifted from crime scenes first undergo photographic documentation and chemical enhancement techniques in order to visualize trace details [8]. Computer analysis then further improves clarity, isolating minute identifying features known as minutiae [9]. Algorithmic extraction of differentiating traits classifies new latent prints, it continuously incorporates the prints enables training of automated comparison systems using along with confirmed suspect identity matches to improve accuracy. Automated classification and matching facilitate identification. The approach scales as the database grows in size without proportionate growth in human effort. Rapid fingerprint evidence analysis accelerates investigations, potentially solving more crimes by linking serial cases through a central digital repository. I aimed to restate the key technical ideas and flow using alternative vocabulary and phrasing while preserving semantic meaning. Please let me know if you need any clarification or have additional requirements for rephrasing the passage.

Study of the fingerprints of a Spanish sample for the determination of the hand and finger

The individuality and permanence of fingerprints make of them a very useful feature in the identification of individuals. There are now automated computer programmes that allow a quick comparison between a fingermark and a database. However, in order to assess the strength of evidence in fingerprint identification, complementary information on the frequencies of the different morphological features of the dermopapillary ridges is required. This idea is used in this work as a starting point to evaluate the frequencies of the parameters used in the determination of the hand and finger in a large sample of 2600 fingerprints taken from 134 male and 127 female Spanish population. Based on these fingerprints, the frequencies of different categories of the following parameters were obtained: type of pattern, slope of the apex ridge, subtype of two-delta pattern, ridge tracing, major angle, major ridge count, bisector, rotation of the central ridge, assimilation to loops and slant. Moreover, the results have shown that these characters are useful for the determination of the hand in whorls (two-delta pattern) and loops (one-delta pattern), but not for the determination of the finger. The most useful and classificatory parameter when determining the hand of origin of a two-delta fingerprint is the slope of the apex ridge, and for the one-delta pattern, knowing the location of the delta allows the correct estimation of the hand of a fingerprint in more than 93% of the cases. The data presented in this paper are novel and can be used by latent print examiners to improve the statistical basis of their decisions in reaching conclusions.

Development of Latent Fingerprints on Different Types of Gloves by Using Physical and Chemical Methods

Fingerprints are a foundation of forensic evidence collected at crime scenes. But what if the perpetrator tries to be clever and wear gloves? Does this automatically mean no fingerprints will be found? Not quite. Latex gloves abandoned at crime scenes can be potential evidence that leaves the perpetrator's hidden fingerprints behind. However, despite their potential, gloves have proven to be a tricky surface for fingerprint development. This study explores the possibility of extracting fingerprints from gloves left behind by criminals. Sweat residues, dirt, and tiny particles trapped on the glove's inner surface can transfer a latent fingerprint, even if it's smudged. This smudged print can still hold valuable clues about the perpetrator. The study aims to observe the effectiveness of fingerprint development on various glove materials: latex, nitrile, cotton, plastic, and silicone. For this, a range of physical and chemical techniques were employed to reveal these hidden prints. Specialized chemicals like ninhydrin, iodine fuming, silver nitrate, Sudan black, and gentian violet were used to make the latent prints visible. Noninvasive approaches like fingerprint powders were also used to develop latent prints on the surface of gloves. This research highlights the ingenuity of forensic science in uncovering evidence even when criminals attempt to mask their identities.

Reliability of ordinal outcomes in forensic black-box studies

Forensic science disciplines such as latent print examination, bullet and cartridge case comparisons, and shoeprint analysis, involve subjective decisions by forensic experts throughout the examination process. Most of the decisions involve ordinal categories. Examples include a three-category outcome for latent print comparisons (exclusion, inconclusive, identification) and a seven-category outcome for footwear comparisons (exclusion, indications of non-association, inconclusive, limited association of class characteristics, association of class characteristics, high degree of association, identification). As the results of the forensic examinations of evidence can heavily influence the outcomes of court proceedings, it is important to assess the reliability and accuracy of the underlying decisions. “Black box” studies are the most common approach for assessing the reliability and accuracy of subjective decisions. In these studies, researchers produce evidence samples consisting of a sample of questioned source and a sample of known source where the ground truth (same source or different source) is known. Examiners provide assessments for selected samples using the same approach they would use in actual casework. These studies often have two phases; the first phase comprises of decisions on samples of varying complexities by different examiners, and the second phase involves repeated decisions by the same examiner on a (usually) small subset of samples that were encountered by examiners in the first phase. We provide a statistical method to analyze ordinal decisions from black-box trials with the objective of obtaining inferences for the reliability of these decisions and quantifying the variation in decisions attributable to the examiners, the samples, and statistical interaction effects between examiners and samples. We present simulation studies to judge the performance of the model on data with known parameter values and apply the model to data from a handwritten signature complexity study, a latent fingerprint examination black-box study, and a handwriting comparisons black-box study.

Unipolar IRT and the Author Recognition Test (ART).

Item response theory (IRT) analyses are often used to evaluate measurement error in educational and psychological test instruments. In such contexts, the latent traits/proficiencies are typically assumed normally distributed and a cumulative normal/logistic measurement link function is applied. Such choices are consistent with constructs that are viewed as bipolar in nature and play a critical role in defining the latent proficiency metric against which the measurement error in the test is evaluated. Recently, alternative models that portray the construct as unipolar have been highlighted as being more appropriate for certain psychopathology and personality constructs. In this paper we extend consideration of unipolar IRT models for a recognition task measure, using several example datasets from various versions of the Author Recognition Test (ART), a measure of print exposure. We show how the decision between unipolar versus bipolar IRT modeling has substantial implications for the quantification and interpretation of measurement error in the ART. In sharp contrast to prior bipolar IRT analyses of the ART, under unipolar IRT measurement error in the ART is minimized at low levels of latent print exposure, and increases as latent print exposure increases. Implications for consideration of unipolar IRT with other constructs and measures (e.g., vocabulary, specialized forms of knowledge) that reflect a similar type of response process are considered in the discussion.

Invariant Feature Encoding for Contact Handprints Using Delaunay Triangulated Graph

Contact-based biometric applications primarily use prints from a finger or a palm for a single instance in different applications. For access control, there is an enrollment process using one or more templates which are compared with verification images. In forensics applications, randomly located, partial, and often degraded prints acquired from a crime scene are compared with the images captured from suspects or existing fingerprint databases, like AFIS. In both scenarios, if we need to use handprints which include segments from the finger and palm, what would be the solution? The motivation behind this is the concept of one single algorithm for one hand. Using an algorithm that can incorporate both prints in a common processing framework can be an alternative which will have advantages like scaling to larger existing databases. This work proposes a method that uses minutiae or minutiae-like features, Delaunay triangulation and graph matching with invariant feature representation to overcome the effects of rotation and scaling. Since palm prints have a large surface area with degradation, they tend to have many false minutiae compared to fingerprints, and the existing palm print algorithms fail to tackle this. The proposed algorithm constructs Delaunay triangulated graphs (DTG) using minutiae where Delaunay triangles form from minutiae, and initiate a collection of base triangles for opening the matching process. Several matches may be observed for a single triangle match when two images are compared. Therefore, the set of initially matched triangles may not be a true set of matched triangles. Each matched triangle is then used to extend as a sub-graph, adding more nodes to it until a maximum graph size is reached. When a significant region of the template image is matched with the test image, the highest possible order of this graph will be obtained. To prove the robustness of the algorithm to geometrical variations and working ability with extremely degraded (similar to latent prints) conditions, it is demonstrated with a subset of partial-quality and extremely-low-quality images from the FVC (fingerprint) and the THUPALMLAB (palm print) databases with and without geometrical variations. The algorithm is useful when partial matches between template and test are expected, and alignment or geometrical normalization is not accurately possible in pre-processing. It will also work for cross-comparisons between images that are not known a priori.

Measuring the rarity of core-delta distances in fingerprint patterns in the Dutch population.

In latent print examination, a conclusion on an individualization is primarily based on the presence of corresponding minutiae. Depending on the level of correspondence between the minutiae on the fingermark and on the reference print, a match is concluded. However, a fingermark is analyzed on all three levels: general pattern combined with core-delta distance, minutiae, and third-level detail. In the opinion of the authors, next to the conclusion based on minutiae, all information should be included in the final assessment of the evidence if present. In this study, we present the results of frequency data on the combination of fingerprint patterns and their core-delta distances. The frequency data allow examiners to substantiate their subjective opinions on the strength of corresponding patterns and core-delta distances based on measurements. The frequencies of the core-delta distances in this study were obtained by encoding core-delta distances in a collection of more than 20,000 fingerprints containing either a loop or a whorl pattern. The frequencies for the core-delta distances of loop patterns were subsequently compared with data from the National Institute of Standards and Technology. This study will demonstrate that core-delta distances in loop and whorl patterns contribute significantly to the overall evidential strength of fingerprint evidence. By adding pattern and core-delta distance information to the evaluation of fingerprint evidence, more challenging fingermarks could be added to fingerprint case reports.

Combining reproducibility and repeatability studies with applications in forensic science

Abstract Studying the repeatability and reproducibility of decisions made during forensic examinations is important in order to better understand variation in decisions and establish confidence in procedures. For disciplines that rely on comparisons made by trained examiners such as for latent prints, handwriting, and cartridge cases, it has been recommended that ‘black-box’ studies be used to estimate the reliability and validity of decisions. In a typical black-box study, examiners are asked to judge samples of evidence as they would in practice, and their decisions are recorded; the ground truth about samples is known by the study designers. The design for such studies includes repeated assessments on forensic samples by different examiners and additionally, it is common for a subset of examiners to provide repeated assessments on the same evidence samples. We demonstrate a statistical approach to analyse the data collected across these repeated trials that offers the following advantages: i) we can make joint inference about repeatability and reproducibility while utilizing both the intra-examiner and inter-examiner data, ii) we can account for examiner–sample interactions that may impact the decision-making process. We demonstrate the approach first for continuous outcomes such as where decisions are made on an ordinal scale with many categories. The approach is next applied to binary decisions and results are presented on the data from two black-box studies.

Shining a Light on Forensic Black-Box Studies

Forensic science plays a critical role in the United States criminal legal system. For decades, many feature-based fields of forensic science, such as firearm and toolmark identification, developed outside the scientific community’s purview. The results of these studies are widely relied on by judges nationwide. However, this reliance is misplaced. Black-box studies to date suffer from inappropriate sampling methods and high rates of missingness. Current black-box studies ignore both problems in arriving at the error rate estimates presented to courts. We explore the impact of each type of limitation using available data from black-box studies and court materials. We show that black-box studies rely on unrepresentative samples of examiners. Using a case study of a popular ballistics study, we find evidence that these nonrepresentative samples may commit fewer errors than the wider population from which they came. We also find evidence that the missingness in black-box studies is non-ignorable. Using data from a recent latent print study, we show that ignoring this missingness likely results in systematic underestimates of error rates. Finally, we offer concrete steps to overcome these limitations. Supplementary materials for this article areavailable online.

Comparison of Derivatization Methods for Groomed Latent Print Residues Analysis via Gas Chromatography

The practice of latent print analysis is comprised of a visual examination and the comparison of the fingerprint pattern from a questioned print to an exemplar(s). When a questioned print is either smudged or contains little pattern detail, the print comparison would be considered an inconclusive determination. However, in these scenarios, the latent print residues (LPRs) could provide associative information to supplement the current ACE-V (Analysis, Comparison, Examination-Verification) process. Advancements using analytical techniques allow for the analysis of LPR chemistry; however, derivatization is generally required to increase the abundance of components not traditionally observed in gas chromatography. This study aimed to determine whether two derivatization reagents, boron trifluoride in methanol (BF3-MeOH) and N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA), provide a better recovery of LPR components from a porous or non-porous substrate. Five volunteers deposited groomed latent print samples onto two substrates: a microfiber filter (porous) and a microscope slide (non-porous). The residues were derivatized or evaporated prior to the gas chromatography-mass spectrometry (GC-MS) analysis. The percent recoveries were higher, >83%, in the DCM extracted samples for both substrates compared to those samples prepared in hexanes. DCM/MSTFA derivatization provided the recovery of fatty acids that ranged from 20 to 30% for both substrates and a recovery of squalene at a rate of 2.37% for the filter sample and 4.2% for the slide sample. These rates were higher than the recovery rates obtained for the hexanes/BF3-MeOH-derivatized samples, with a range of 1–8% for the fatty acids recovery rates and 0.6–0.85% for squalene from both substrates. Overall, the MSTFA derivatization reagent produced higher recoveries for LPR on porous and non-porous substrates while providing a LPR chromatographic profile similar to that of a non-derivatized sample. The use of DCM as a solvent provided a wider range of LPR components recovered than hexanes and, thus, should be used as the extraction solvent when derivatizing samples, regardless of the substrate.

Modern Methods of Latent Print Development I - Physical Methods

Aim: The first half of the two-part study presents the physical methods of latent print developments, method classification, brief history, and future trends.Methodology: The study synthesizes some of the most important technical handbooks and dozens of articles, published in the last decades. It also includes my own previously published research results.Findings: The so-called physical methods of latent print development are still under ongoing research. Methods from the 19th century, like powdering, are still being developed. VMD has once been replaced by cyanoacrylate fuming in the late seventies, but in the last 1-2 years it is spreading again.Value: In the Hungarian literature, such a comprehensive review has not beenpublished on this subject for a long time.

Latent Fingerprint Development by Brick Powder

In forensic investigations, the relationship between the criminal, the victim, and the crime scene can be firmly established through the detection of latent finger marks. Fingerprints are avital and unique identity of a person. These are impressions left by the friction ridges of a human finger on contact with any surface. Many unique characteristics in the human body like a fingerprint, DNA, palm prints, iris patterns, voices, etc. So, Fingerprint is a unique characteristic of the human body, and every human’s different fingerprints between identical twins. As we know friction ridges develop in a 3-4 month of gestation duration time. Mayer, a German doctor, and anatomist were the first to write that friction ridge skin is unique. The fingerprint is the most important evidence at the Crime scene and identification of the criminal. Fingerprint identification is a method of identification using the impression formed by the minute ridges seen on the fingertips. Fingerprint has certain individual characteristics that are unique. Latent fingerprints are most generally seen prints from the crime scene. Such prints are obtained when natural oils and perspiration existing between the fingertip ridges are transferred to a surface by any contact. Latent prints are invisible and are much harder to detect and preserve. In this research paper, a new method for the development of Latent fingerprints is used that’s brick powder. The brick powder is used in various Porous and Non-porous surfaces like plastic glass, ordinary mirror, matchbox, painted wall, writable CD, wooden substrate, currency note, door handle, floor surface, book cover, sunglasses, and mobile glass card for development of latent fingerprint impression.

Hierarchical Bayesian non-response models for error rates in forensic black-box studies.

Forensic science plays a critical role in the United States criminal legal system. Historically, however, most feature-based fields of forensic science, including firearms examination and latent print analysis, have not been shown to be scientifically valid. Recently, black-box studies have been proposed as a means of assessing whether these feature-based disciplines are valid, at least in terms of accuracy, reproducibility and repeatability. In these studies, forensic examiners frequently either do not respond to every test item or select an answer equivalent to 'don't know'. Current black-box studies do not account for these high levels of missingness in statistical analyses. Unfortunately, the authors of black-box studies typically do not share the data necessary to meaningfully adjust estimates for the high proportion of missing responses. Borrowing from work in the context of small area estimation, we propose the use of hierarchical Bayesian models that do not require auxiliary data to adjust for non-response. Using these models, we offer the first formal exploration of the impact that missingness is playing in error rate estimations reported in black-box studies. We show that error rates currently reported as low as 0.4% could actually be at least 8.4% in models accounting for non-response where inconclusive decisions are counted as correct, and over 28% when inconclusives are counted as missing responses. These proposed models are not the answer to the missingness problem in black-box studies. But with the release of auxiliary information, they can be the foundation for new methodologies to adjust for missingness in error rate estimations. This article is part of the theme issue 'Bayesian inference: challenges, perspectives, and prospects'.

Synthesis and spectroscopic characterization of fluorescent 3-acetyl-4-hydroxy coumarin for biomedical and latent fingerprint applications

The fluorescent 3-acetyl-4‑hydroxy coumarin (AcHyC) development for DNA binding affinity and latent fingerprint detection under UV illumination has not yet been adequately researched. In this sense, this work presents the fabrication and characterization of AcHyC for DNA binding and latent fingerprint applications. Based on electronic absorption spectroscopy, AcHyC was bound to DNA with a significantly high binding constant (2.9 × 106M−1). The interaction of AcHyC with DNA has also been examined using molecular docking analysis, which supports earlier spectroscopic data. The photoluminescence emission and the lifetime of AcHyC were measured. AcHyC exhibited intensive yellowish-green luminescence with spectacular visual emission under unharmful UVA and UVB excitation. Based on the highly luminescent character of AcHyC, latent print details, including their characteristic three levels, have been identified from various forensic substrates (non-porous, semi-porous, and porous).

Development of Improved DNA Collection and Extraction Methods for Handled Documents

Handwritten documents may contain probative DNA, but most crime laboratories do not process this evidence. DNA recovery should not impair other evidence processing such as latent prints or indented writing. In this study, single fingermarks on paper were sampled with flocked swabs, cutting, and dry vacuuming. In addition, two extraction methods were compared for the sample type. DNA yields were low across all methods; however, this work confirms the ability to recover DNA from paper and the usefulness of the vacuum sampling method combined with the Chelex-Tween method. Stability of touch DNA deposits were compared over an 11-month period to better understand degradation that may occur over time. No significant difference in DNA recovery was observed, suggesting DNA deposits on paper are stable over an 11-month span.