Fingerprint Residues Research Articles

Review on development of wet latent fingerprints by small particle reagent

Small particle reagent technique is a method which is used to develop fingermarks on moist and smooth surfaces. It consist the theory of adherence of fine particles which is suspended in a treating solution to the oily or fatty components (water insoluble) present in in latent fingermark residue and gives a grey colored deposit. It is also considered as belonging to the family of powder dusting. The effectiveness of this technique can be increased by using fluorescent dyes in it's treating solution which can also detect faint fingermarks on multi-colored surfaces. Small particle reagent involves the use of synthetic detergent which was here replaced by saponin extracted from the fruit of Sapindus mukorossi as natural detergent. The other ingredient used in the formulation is black charcoal powder. This composition develops sharp and clear fingermarks on non-adsorbent surfaces like glass, metal sheet, plastic, laminated wood, ceramic tiles and compact discs after these were immersed in water for variable periods of time. The ability of the present formulation to detect weak chance prints not only enhances its utility, but also its potentiality in forensic investigations. The raw materials used to prepare the SPR are easily available and cost-effective.

Chemical composition of the fingermark residue: Assessment of the intravariability over one year using MALDI-MSI

These past years, the chemical composition of fingermarks have attracted interest of researchers to meet multiple objectives like the determination of an individual’s age, gender or lifestyle or the impact of some fingermark detection processes, to cite a few. These studies have highlighted the need to investigate the consistency of the fingermark composition over time. This research explores the evolution of the secretion residue composition of thirteen donors over one year, focusing on the intravariability. The dual use of Matrix-Assisted Laser Desorption/Ionisation Mass Spectrometry Imaging (MALDI-MSI) and chemometrics provided valuable data regarding the evolution of composition over time as well as the consistency of presence of hundreds of compounds.

Latent Fingerprint Enhancement on Metallic Surfaces Using Electroactive Film Deposition Combined with Electrochemically Driven Dye Encapsulation

Criminal investigations require establishment of the identities of suspects, victims and witnesses. The most common physical evidence that accomplishes this is a fingermark: it is unique to an individual and time-invariant. Its presence can establish contact between an individual and an object or place the individual at a crime scene. In practice, most such marks are latent (non-visible) fingermarks: these require chemical or physical treatment to render a visible image. Typical chemical treatments involve interaction of a reagent (powder, cyanoacrylate, dye) with the fingerprint residue. Deterioration or loss of residue due to environmental exposure limits the efficacy of these treatments. The success rate for developing a latent mark to a standard permitting a legally acceptable identification is only ca. 10%; this motivates new chemical approaches.In a complementary strategy, we have used the fingerprint residue as a template (“mask”) to direct electrochemically generated reagent to the bare surface between the deposited ridges, thereby creating a negative image of the fingerprint. On metallic substrates the deposition and viewing processes may be controlled electrochemically. This offers the promise of application to a range of objects forensically relevant to both violent crime (knives, guns, bullet casings) and volume crime (tools, handles at points of entry and metal theft). This templating concept was originally demonstrated using electrodeposited polyaniline [1] and PEDOT [2] films, whose electrochromic properties were used to optimize the visual contrast within the fingerprint image. We subsequently extended this concept through the use of electrodeposited poly(pyrrole-co-3,4-ethylenedioxythiophene) copolymers of varying composition to provide wider and more subtle variation of optical properties (simplistically, colour) [3]. Through deliberate selection of co-monomer feedstock, polymer deposition potential and subsequent “viewing” potential, one could then pre-select bespoke material characteristics optimized to a specific substrate.Here we further extend the concept by the inclusion of the dyes Methyl Red (MR), Methyl Orange (MO), Indigo Carmine (IC) or Basic Yellow 40 (BY) into electrodeposited polypyrrole (PPy) films by a combination of electrostatic and/or physical entrapment. The substrates were stainless steel electrodes, upon which a latent fingerprint had been deposited. The deposition medium was an aqueous pyrrole (0.05 mol L-1) / dye (0.005 mol L-1) solution. In the case of MR, sodium dodecylsulphate (0.005 mol L-1) was employed to improve dye solubility. We compare the effectiveness of potentiostatic (0.90 – 1.00 V vs. Ag/AgCl) and galvanostatic (2.5 – 5.0 mA cm-2) deposition control functions. The extent of polymer deposition was varied via deposition time (60 to 300 s) and coulometrically assayed.Dye encapsulation was qualitatively apparent as the polypyrrole films presented the colour of the dye used as dopant: PPy/MR and PPy/MO films were reddish-brown, and PPy/IC was blue. Complementary to these colours seen via absorbance, the emission properties of BY (widely used in conjunction with cyanoacrylate) are also apparent via fluorescence when irradiated with UV light. We will present and interpret images demonstrating how these all these composite electroactive materials yield excellent colour contrast between the surface and the fingerprint. Specifically, one can readily identify the so-called second level features that, in conjunction with dactyloscopy images, unambiguously identify individuals or establish connections between crime scenes. The advantages of this approach, alone and in combination with conventional visualization techniques, will be discussed.

Sequence and structural conservation reveal fingerprint residues in TRP channels.

Transient receptor potential (TRP) proteins are a large family of cation-selective channels, surpassed in variety only by voltage-gated potassium channels. Detailed molecular mechanisms governing how membrane voltage, ligand binding, or temperature can induce conformational changes promoting the open state in TRP channels are still a matter of debate. Aiming to unveil distinctive structural features common to the transmembrane domains within the TRP family, we performed phylogenetic reconstruction, sequence statistics, and structural analysis over a large set of TRP channel genes. Here, we report an exceptionally conserved set of residues. This fingerprint is composed of twelve residues localized at equivalent three-dimensional positions in TRP channels from the different subtypes. Moreover, these amino acids are arranged in three groups, connected by a set of aromatics located at the core of the transmembrane structure. We hypothesize that differences in the connectivity between these different groups of residues harbor the apparent differences in coupling strategies used by TRP subgroups.

Leaving a mark on forensic science: how spectroscopic techniques have revealed new insights in fingerprint chemistry

Despite a multitude of chemical and physical methods capable of detecting fingerprint residues, there are substantial challenges with fingerprint recovery. Spectroscopic methods have played a critical role in the analysis of fingerprints, used to identify the chemical constituents present, examine their degradation over time and compare the chemical variation between donors.

Monitoring the chemical changes in fingermark residue over time using synchrotron infrared spectroscopy.

Degradation of fingermark residue has a major impact on the successful forensic detection of latent fingermarks. The time course of degradation has been previously explored with bulk chemical analyses, but little is known about chemical alterations within specific regions of the fingermark, which is difficult to study with bulk measurement. Here we report the use of synchrotron-sourced attenuated total reflection-Fourier transform infrared (ATR-FTIR) microspectroscopy to provide spatio-temporal resolution of chemical changes within fingermark droplets, as a function of time since deposition, under ambient temperature conditions. Eccrine and sebaceous material within natural fingermark droplets were imaged on the micron scales at hourly intervals from the time of deposition until the first 7-13 hours after deposition, revealing that substantial dehydration occurred within the first 8 hours. Changes to lipid material were more varied, with samples exhibiting an increase or decrease in lipid concentration due to the degradation and redistribution of this material. Across 12 donors, it was noticeable that the initial chemical composition and morphology of the droplet varied greatly, which appeared to influence the rate of change of the droplet over time. Further, this study attempted to quantify the total water content within fingermark samples. The wide-spread nature and strength of the absorption of Terahertz/Far-infrared (THz/Far-IR) radiation by water vapour molecules were exploited for this purpose, using THz/Far-IR gas-phase spectroscopy. Upon heating, water confined in natural fingermarks was evaporated and expanded in a vacuum chamber equipped with multipass optics. The amount of water vapour was then quantified by high-spectral resolution analysis, and fingermarks were observed to lose approximately 14-20 μg of water. The combination of both ATR-FTIR and Far-IR gas-phase techniques highlight important implications for experimental design in fingermark research, and operational practices used by law enforcement agencies.

Whether and When Superhydrophobic/Superoleophobic Surfaces Are Fingerprint Repellent.

Driven by the ever-increasing demand for fingerprint-resistant techniques in modern society, numerous researches have proposed to develop innovative antifingerprint coatings based on superhydrophobic/superoleophobic surface design. However, whether superhydrophobic/superoleophobic surfaces have favorable repellency to the microscopic fingerprint is in fact an open question. Here, we establish a reliable method that enables evaluating the antifingerprint capability of various surfaces in a quantitative way. We show that superhydrophobicity is irrelevant with fingerprint repellency. Regarding superoleophobic surfaces, two distinct wetting states of microscopic fingerprint residues, i.e., the “repellent” and the “collapsed” states, are revealed. Only in the “repellent” state, in which the fingerprint residues remain atop surface textures upon being pressed, superoleophobic surfaces can bring about favorable antifingerprint repellency, which correlates positively with their receding contact angles. A finger-deformation-dependent intrusion mechanism is proposed to account for the formation of different fingerprint wetting states. Our findings offer important insights into the mechanism of fingerprint repellency and will help the design of high-performance antifingerprint surfaces for diverse applications.

Production of artificial fingermarks. Part I – Synthetic secretions formulation

Fingermark variability is a critical parameter. To mitigate the effects of this variability, synthetic secretions in the form of simple mixtures of target compounds found in eccrine sweat have been described in the literature, but they are usually reactive towards only a minimal range of detection techniques. If this approach is acceptable for the production of single-technique test strips, such artificial secretions cannot be considered as reliable fingermark simulants because they do not reproduce the complex matrix that makes up real secretions. Research has shown that sebaceous and eccrine compounds are probably present simultaneously in fingermark residue in the form of an emulsion. This paper is the first part of a research project that aims at producing realistic artificial fingermarks containing an extensive range of eccrine and sebaceous compounds. This first study aimed to reproduce and compare two synthetic fingermark residues formulations and assess their potential to be used as fingermark simulants. Spot tests of the artificial secretions were deposited on paper substrates, and their reactivity with four common detection techniques was tested: 1,2-indanedione-zinc, ninhydrin, oil red O, and physical developer. Both formulations showed very good results when processed with the two amino acid reagents, as well as oil red O, and no obvious differences were observed between the two versions. The results obtained with the physical developer were inconsistent and demonstrated that the fundamental working principle of physical developer needs to be further understood. The results were extremely promising as they showed the potential of such reproducible artificial secretions to be used to assess an extensive range of detection techniques, which would be highly beneficial to guarantee better research and quality control in fingermark detection. The use of spot tests to deposit the simulant was shown to be unreliable and a more controllable and reproducible deposition method using an inkjet printer will be presented in the second part of this research.

Functionalization of pyrrole derivatives as a way to improve their solubility in aqueous medium for applying in latent fingerprints development

Latent fingerprints (LFPs) play an important rule for criminal investigations regarding to the identification and connection of an individual to a crime scene. Herein, we report a non-destructive method for LFPs development based on the electropolymerization of pyrrole derivatives modified with water-soluble groups on stainless steel surfaces containing fingerprint residues. The polymers, namely P1, P2, P3 and P4, and a copolymer of 4 with 3,4-ethylenedioxythiophene P(4-co-EDOT) were electrodeposited by oxidation of the monomers in aqueous LiClO4 by applying potentials (E) of 1.25–1.7 V vs. Ag/AgCl or current density (j) of 5.0–10 mA cm−2 for 15–240 s. The quality of the developed fingerprint images was verified by Scanning Electron Microscopy, the Griaule Forensic Fingerprint® software and the Bandey classification system. It was possible to observe the enhancement of the visual contrast between the surface and the fingerprint residues, providing high quality images of the developed fingerprints.

DNA recovery after sequential processing of latent fingerprints on copy paper.

Forensic examiners must determine whether both latent fingerprint development and DNA profiling can be performed on the same area of an evidence item and, if only one is possible, which examination offers the best chance for identification. Latent fingerprints can be enhanced by targeting different components of fingerprint residues with sequential chemical treatments. This study investigated the effects of single‐reagent and sequential latent fingerprint development processes on downstream DNA analysis to determine the point at which latent fingerprint development should be stopped to allow for DNA recovery. Latent fingerprints deposited on copy paper by one donor were developed using three sequential processes: 1,8‐diazafluoren‐9‐one (DFO) → ninhydrin → physical developer (PD); 1,2‐indanedione‐zinc (IND‐Zn) → ninhydrin → PD; and IND‐Zn → ninhydrin → Oil Red O (ORO) → PD. Samples were examined after the addition of each chemical treatment. DNA was collected with cotton swabs, extracted, quantified, and amplified. DNA yields, peak heights, number of alleles obtained, and percentage of DNA profiles eligible for CODIS upload were examined. DNA profiles were obtained with varying degrees of success, depending on the number and type of treatments used for latent fingerprint development. The treatments that were found to be the least harmful to downstream DNA analysis were IND‐Zn and IND‐Zn/laser, and the most detrimental treatments were DFO, DFO/laser, and PD. In general, as the number of treatments increase, the opportunities for DNA loss or damage also increase, and it is preferable to use fewer treatments when developing latent fingerprints prior to downstream DNA processing.

Sensitive and rapid detection of fingerprints based on electrospun nanofibrous membranes and quantum dots

Fingerprints are the unique features of individuals, and the inefficient and time-consuming detection methods limit their wider application in the field of personal information identification. In this study, a new strategy is proposed for effective and rapid detection of fingerprints based on electrospun nanofibrous membranes and quantum dots (QDs). The prepared membranes had nano-scale pores structures and fibers, and the fingerprint residues could stably adhere to the nanofibers through non-specific adsorption to achieve the stability of the fingerprint morphology after the finger being pressed on the membrane. Due to the hydrophobic interactions between QDs and fingerprint residues, bright UV-irradiated emission of fingerprints pattern with precise level 3 details can be recorded after the membrane being immersed in the QDs solution for only 30 s. More importantly, the obtained fingerprints were invisible in sunlight, which is critical for fingerprint encryption. Besides, the results revealed that the latent fingerprints (LFPs) on the surface of different substrates could be transferred by the membranes and be developed by QDs. This study provides a promising method to achieve the precise detection and complete storage of fingerprints information.

Visualizing shed skin cells in fingerprint residue using dark-field microscopy.

This proof-of-concept study shows that dark-field microscopy provides sufficient contrast for cell visualization in fingerprints with high sebum content. Although the application is limited to smooth surfaces that do not scatter light, such as polyethylene terephthalate (PET), it was able to measure the number of cells deposited within a fingerprint residue and the reduction in cell transfer with repeated skin contact. On a PET surface, at roughly 5N of contact force, a typical finger transfers several hundred cells onto the surface. Over subsequent finger contacts onto a clean PET surface, this number decreased exponentially until a steady state was reached, which is characterized by the transfer of (78±36) cells or (0.46±0.21) cells/mm2 when normalized for fingerprint area. High uncertainty in cell transfer was due to: the highly variable nature of a human finger (where the number of loose cells varies from person to person and from day to day depending on what they touch) and difficulties in controlling the contact force and finger movement such as twisting during deposition (where twisting of the finger can expose a new patch of skin to the substrate, increasing the number of cell transfer). Plasma etching was also explored as an effective way to validate dark-field microscopy for cell counting. Although limited to inorganic substrates due to etching effects, exposing the fingerprint for less than 10min can remove a majority of the sebum while keeping the cells intact for a before-and-after comparison using light microscopy.

Impact of surface roughness on the deposition of saliva and fingerprint residue on non-porous substrates

A diverse range of non-porous substrate surfaces routinely encountered in crime scene settings were evaluated for their affinity towards deposited saliva and fingerprint residue. Raman spectroscopy, atomic force microscopy (AFM), field-emission scanning electron microscopy (FE-SEM) and water contact angle measurements were employed to quantitatively and qualitatively evaluate the physicochemical variables impacting the deposition of touch and salivary deposits. It was established that small changes in surface roughness and physicochemical interactions, including hydrophobicity, resulted in observable impacts on the spread of salivary deposits and deposition of fingerprint residue. It was further identified that not only did the surface free energy (SFE) available to the deposit, measured through water contact angles, influence the deposition and spread of the material on the surface, but that the nature of the deposit further impacted these dynamics. This preliminary study has developed a platform to gain a better understanding of the importance of surface roughness as a consideration, when interrogating how forensically relevant deposits such as saliva and fingerprint residue interact with non-porous surfaces. This better understanding is necessary when reflecting on the successfulness of recovering DNA, when considering means to improve recovery of trace samples from crime scenes, and when improving assessment of the likelihood of transfer of a deposit from one substrate to another upon contact.

Electrochemical development and enhancement of latent fingerprints on stainless steel via electrochromic effect of electrodeposited Co3O4 films

Latent fingerprints are one of the most important trace evidences at crime scenes that can be used for individual recognition. The invisible nature of latent fingerprints gives rise to various kinds of development and imaging techniques, among which a number of electrochemical methods are receiving increasing attention. We report herein a new interfacial strategy based on spatially selective electrodeposition of Co3O4 films with electrochromic properties to develop and enhance latent fingerprints on stainless steel surfaces. During the development process by potentiostatical deposition of Co3O4 on the background, image contrast and development accuracy as two key factors that measure the effectiveness of fingerprint development are systemically evaluated from millimeter to microscopic scales. Three levels of morphological features in latent fingerprints can be well developed. Optical properties of deposited Co3O4 films can be reversibly adjusted by changing applied potential. This phenomenon is analyzed qualitatively through visual appraisal and determined quantitatively by using color channels. The results indicate that image enhancement of developed fingerprints can be easily accomplished by extracting the blue channel of captured images. Forensic DNA typing is also performed to reveal the impact of this method on DNA evidence in fingerprint residues. The ratio of detected loci reaches 80.9% after electrochemical process. This novel method has advantages including high development accuracy, adjustable image contrast, and relatively non-destructive to DNA analysis.

Latent fingerprint development by using silver nanoparticles and silver nitrate-A comparative study.

The beginning of latent fingerprint development on porous surface was first achieved by silver nitrate (AgNO3 ) method. But the significantly increasing cost has caused forensic experts to look for an alternative means. Silver nitrate (AgNO3 ) is the main component in the synthesis of metal nanoparticles, namely silver nanoparticles (AgNPs). Owing to its unique property to adhere with fingerprint residue, AgNPs have attracted a great attention in the domain of nano-forensic fingerprinting. This study mainly focuses on the use of lower concentration of silver nitrate through new AgNP development method. The AgNPs were synthesized by wet chemical method with different molar concentrations (0.1, 0.01, and 0.001M) of silver nitrate, characterized by ultraviolet visible spectrophotometer and high-resolution transmission electron microscope (HR-TEM). The average diameter of AgNPs calculated by HR-TEM was 10.66±1.22nm at 0.1M, 12.50±2.64nm at 0.01M, and 14.44±2.68nm at 0.001M, respectively. A comparative analysis was also carried out to see the quality and stability of fingerprints produced on paper or porous substrate by using AgNO3 and AgNPs, respectively. During the study, AgNPs were able to develop distinct ridge details and were found to be stable for more than a month. Comparatively, when AgNO3 was used as the developing agent for the latent fingerprints, only faint ridge patterns were observed which further showed degradation of fingerprint stability within about 20days. Overall, the current AgNP method showed good visibility and stability by using lower concentration of silver nitrate which can be used in place of conventional AgNO3 method.

To glove or not to glove? Investigations into the potential contamination from handling of paper-based cultural heritage through forensic fingerprinting approaches

The handling of cultural heritage objects has become a highly debated topic in the last decade. The work and outcomes described in this paper are aimed to provide objective data to assist in making appropriate decisions as to whether or not wearing gloves is appropriate in a given situation. The forensic fingermark development techniques of 1,2-indandione and single metal deposition II were used to investigate the efficacy of handwashing and glove use to improve the information available when deciding whether to use gloves when handling paper objects. It was found that fingermarks did not permeate through polymer glove types but could through cotton gloves. It was also shown that the amounts of observable fingermark residues were greater 5 min after handwashing than if handwashing had not occurred, undermining previous arguments for not wearing gloves if hands could be washed before object handling.

Evaluation of alizarin and purpurin dyes for their ability to visualize latent fingermark on porous surfaces

Anthraquinones are a group of dye with many members and a wide range of industrial uses ranging from food, textiles to printing. Even though the reactions of anthraquinone dyes with amino acids are known, they have not yet been subjected to an examination regarding their ability in fingermark detection. In the presented study, the potential of alizarine and purpurin, natural anthraquinone dyes, as a fingermark reagent was examined in comparison with ninhydrin and lawsone. Alizarin and purpurin react with latent fingermark residue on copier paper and thermal paper to yield yellow-orange coloured impressions. The products formed also display photoluminescence properties when illuminated at 440 nm viewed through red filter. Both natural anthraquinone dyes exhibited some superior properties at the development of latent fingermarks on these surfaces compared to ninhydrin and lawsone.

A user-secure and highly selective enhancement of latent fingerprints by magnetic composite powder based on carbon dot fluorescence

A novel bifunctional composite powder with moderate magnetic properties and intense fluorescence was prepared via a layer-by-layer assembly route. After the self-assembly procedure run up to 7 times, the as-prepared Fe3O4@SiO2-CD(n) began to overcome the quenching effect from Fe3O4 nanoparticles and shown intense blue emission (λem = 434 nm) under 370 nm UV irradiation with a quantum yield of 45.04%. The morphological characterization revealed that it has a spherical and uniform core-shell structure of approximately 120 nm in diameter. The component analysis and contact angle test manifested the hydrophilic groups on the surface of the final products. As a result, this novel nanocomposite powder has two advantages over traditional fingerprint powder in both morphology/size and organic functional groups, which could provide more suitable physical adsorption and more chemical bonding in the interaction between fingerprint residues and powders. A series of fingerprint enhancement experiments and a novel quantitative evaluation both confirmed its high contrast, high sensitivity, and especially high selectivity over traditional methods for latent fingerprints. More importantly, in addition to its saturation magnetization of 6.4 emu/g, the abundant hydrophilic groups on the surface of our composite powder also played an important role in absorbing moisture in air and print residues to avoid powder dust from the user’s respiratory tract. Therefore, a fast, user-secure, and highly selective method was established and expected to be valuable in forensic science and related fields.

Acetylated cashew-gum-based silver nanoparticles for the development of latent fingerprints on porous surfaces

Fingerprints have been used in forensic investigations as a powerful tool for human identification. However, it is desirable to find new sustainable sources and synthesis for fingerprint developers, in order to reduce the production costs, to improve the sensitivity and to reduce environment impact after the disposal. This report describes a study involving the production of acetylated cashew-gum-based silver nanoparticles (ACG-AgNPs), using three concentrations of ACG (0.5, 1.0 and 5.0 mg/mL). The nanoparticles were characterized by UV-VIS spectroscopy, AFM (atomic force microscopy) and TEM (transmission electron microscopy). In addition, computer simulations and evaluation of their effect as a potential fingerprint developer on paper were studied, using ninhydrin as a positive control. The results showed that samples were able to reveal the lines contained in the fingerprint residues on paper. Positive results were obtained for all the samples in tests performed 1, 6 and 24 h after application. Howeverthe best performance was observed with the sample containing ACG 0.5 mg/mL. ACG-AgNPs have potential for practical and rapid latent fingerprint development on porous surfaces, which allows the development of a product to be used even at the crime scene. Another advantage was the synthesis process: simple, fast, low-cost and using a biocompatible and biodegradable material as stabilizer, providing a non-toxic material. In addition, this material, is likely to cause less environmental damage than the reagents used by conventional techniques.

Vacuum metal deposition enhancement of friction ridge detail on ballistic materials

The efficacy of Gold/Zinc and Silver/Zinc vacuum metal deposition (VMD) protocols were assessed as stand-alone methods of fingermark enhancement on ballistic brass materials. The results demonstrate the effectiveness of VMD enhancement on a large pool of donors (n = 20), with potentially identifiable marks recovered for the majority of donors, including samples aged up to two months. Of the 20 donors a subset of six donors were selected to assess the capability of VMD enhancement on brass fired cartridge cases, from which some friction ridge detail (FRD) was recovered. Lastly, an attempt to understand which fingermark components are facilitators of VMD enhancement was made. Fingermark residue was extracted from brass tiles and fired cartridge cases before analysing chromatographically (GC–MS). Although some key components were indicated, further evaluation of all fingermark components is needed to draw firm conclusions as to the role each plays in VMD enhancement.