An investigation into the detection of latent marks on the feathers and eggs of birds of prey

There are numerous enhancement techniques (physical and chemical) which have been developed for the successful visualisation of latent fingermarks. Nonetheless, problems arise when latent fingermarks require enhancement on difficult surfaces such as human skin, food stuffs, fabric and animals. The ability to develop latent fingermarks on the surface of bird of prey feathers and that of their eggs was investigated. Red and green magnetic fluorescent powders proved to be most suitable on the surface of bird of prey feathers whereas black magnetic powder was the most suitable technique on the eggs. These powders produced the highest quality of visible ridge-detailed developments over a controlled period of time

Evaluation of current methods for processing bloody fingerprints on non-porous substrates exposed to various contaminants

Blood is a common type of medium with which patent fingerprints are deposited at crime scenes. Chemical enhancements are generally used on bloody fingerprints when some type of pattern is visible but ridge characteristics are not sufficiently defined to make the print suitable for comparison. Motor vehicles, which may be associated with crimes scenes or forensic investigations, can be exposed to a variety of contaminants from the environment, including mud, salt, pollen, dust and motor oil, as well as from the application of chemicals to protect the paint such as car wax and car polish. It is unknown if these contaminants in combination with the chemicals used to enhance bloody impressions or in combination with the blood itself, could impact the enhancement of bloody impressions found on vehicles. This study seeks to assess the effectiveness of a selection of blood enhancement methods in the presence of such contaminants. Three of the four enhancement chemicals that were tested, Amido Black, Hungarian Red, and Leucocrystal Violet, were determined to be similarly effective for the enhancement of bloody friction ridge patterns applied to the surfaces of contaminated glass and metal substrates

Chemical enhancement of soil-based marks on nonporous surfaces followed by gelatin lifting

This study assessed the use of processing techniques (potassium thiocyanate, 2-2-dipyridil, potassium ferrocyanide, ammonium pyrrolidinedithiocarbamate, safranin, magnetic powder) for the enhancement of soil-based marks on nonporous surfaces, followed by gelatin lifting for the recovery of these marks. Other variables in the study included the use of nonporous substrates with varying colors (ceramic tiles, glass, linoleum, plastic bags, leaflets) and different aging periods (1, 7, 14, and 28 days) prior to enhancement and gelatin lifting. A numerical grading system from -1 (deterioration) to 4 (recovery of all fine detail) was adopted to assess the quality of the enhancement achieved.In this study, the two most effective chemical enhancement techniques for soil-based marks on nonporous surfaces were safranin and potassium thiocyanate, specifically on grey linoleum and white ceramic tiles. One-day aging of soil-based marks provided poor results, whereas 28-day aging periods provided superior enhancement. In general, lifting with gelatin lifts provided further improvement on the initial enhancement, by means of contrast and sharpness. However, the use of gelatin lifting sometimes resulted in the deterioration of the original mark. Marks treated with safranin and lifted with white gelatin lifts provided even further improvement through fluorescence examination

A Universal Latent Fingerprint Enhancer Using Transformers

Forensic science heavily relies on analyzing latent fingerprints, which are crucial for criminal investigations. However, various challenges, such as background noise, overlapping prints, and contamination, make the identification process difficult. Moreover, limited access to real crime scene and laboratory-generated databases hinders the development of efficient recognition algorithms. This study aims to develop a fast method, which we call ULPrint, to enhance various latent fingerprint types, including those obtained from real crime scenes and laboratory-created samples, to boost fingerprint recognition system performance. In closed-set identification accuracy experiments, the enhanced image was able to improve the performance of the MSU-AFIS from 61.56\% to 75.19\% in the NIST SD27 database, from 67.63\% to 77.02\% in the MSP Latent database, and from 46.90\% to 52.12\% in the NIST SD302 database. Our contributions include (1) the development of a two-step latent fingerprint enhancement method that combines Ridge Segmentation with UNet and Mix Visual Transformer (MiT) SegFormer-B5 encoder architecture, (2) the implementation of multiple dilated convolutions in the UNet architecture to capture intricate, non-local patterns better and enhance ridge segmentation, and (3) the guided blending of the predicted ridge mask with the latent fingerprint. This novel approach, ULPrint, streamlines the enhancement process, addressing challenges across diverse latent fingerprint types to improve forensic investigations and criminal justice outcomes

Polarization- and Specular-Reflection-Based, Non-contact Latent Fingerprint Imaging and Lifting

In forensic science the finger marks left unintentionally by people at a crime scene are referred to as latent fingerprints . Most existing techniques to detect and lift latent fingerprints require application of certain material directly onto the exhibit. The chemical and physical processing applied onto the fingerprint potentially degrades or prevents further forensic testing on the same evidence sample. Many existing methods also come with deleterious side effects. We introduce a method to detect and extract latent fingerprint images without applying any powder or chemicals on the object. Our method is based on the optical phenomena of polarization and specular reflection together with the physiology of fingerprint formation. The recovered image quality is comparable to existing methods. In some cases like the sticky side of a tape our method shows unique advantages

Fabrication of a Self-Assembled and Flexible SERS Nanosensor for Explosive Detection at Parts-Per-Quadrillion Levels from Fingerprints

Apart from high sensitivity and selectivity of surface-enhanced Raman scattering (SERS)-based trace explosive detection, efficient sampling of explosive residue from real world surfaces is very important for homeland security applications. Herein, we demonstrate an entirely new SERS nanosensor fabrication approach. The SERS nanosensor was prepared by self-assembling chemically synthesized gold triangular nanoprisms (Au TNPs), which we show display strong electromagnetic field enhancements at the sharp tips and edges, onto a pressure-sensitive flexible adhesive film. Our SERS nanosensor provides excellent SERS activity (enhancement factor = ∼6.0 × 106) and limit of detection (as low as 56 parts-per-quadrillions) with high selectivity by chemometric analyses among three commonly military high explosives (TNT, RDX, and PETN). Furthermore, the SERS nanosensors present excellent reproducibility (<4.0% relative standard deviation at 1.0 μM concentration) and unprecedentedly high stability with a “shelf life” of at least 5 months. Finally, TNT and PETN were analyzed and quantified by transferring solid explosive residues from fingerprints left on solid surfaces to the SERS nanosensor. Taken together, the demonstrated sensitivity, selectivity, and reliability of the measurements as well as with the excellent shelf life of our SERS nanosensors obviate the need for complicated sample processing steps required for other analytical techniques, and thus these nanosensors have tremendous potential not only in the field of measurement science but also for homeland security applications to combat acts of terror and military threats

Investigation into the effect of fingermark detection chemicals on the analysis and comparison of pressure-sensitive tapes.

Pressure sensitive tapes such as duct tape are a common trace type sent for forensic analysis. The limited variation of tape backings and adhesives can provide valuable linkage evidence between a scene, a victim or a person of interest. Fingermarks are also often found on tapes and prioritised over tape analyses. This project aimed to investigate the effects of fingermark enhancement chemicals, namely Wet Powder™, cyanoacrylate and cyanoacrylate stained with rhodamine 6G, on various tapes and their comparison with untreated tapes. The changes in physical and optical features were observed using a Video Spectral Comparator (VSC) and microscopy. Chemical changes were analysed by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). Most physical and optical properties were not heavily affected by the treatments. An increase in fluorescence was observed with specimens stained with rhodamine 6G as might be expected. Significant chemical changes were observed in the FTIR spectra produced from cyanoacrylate fuming. Polyethylene backings and rubber adhesives were heavily affected while polypropylene backings were moderately affected. Cellulose backings, polyester and polyacrylate adhesives were not significantly affected. Wet Powder™ treatment proved useful for enhancing fingermarks on most adhesives while leaving behind little chemical residue that might interfere in a forensic comparison

Recovery of fingermarks from surfaces previously considered to be problematic within practice

Fingerprints are an important type of evidence within the criminal justice system, and these have been used for multiple purposes since the 19th century. Within forensic investigation these are primarily used for identification and/or elimination purposes. Numerous methods and techniques, including physical and chemical procedures, are used to enhance and recover fingermarks from surfaces. However, there are continuing surface and exhibit types which are considered to be problematic to develop and recover within practice. The purpose of this research was to overcome some of these issues focusing specifically on fingerprints in/on anti-climb paint, leaves, and feathers. The effectiveness of cyanoacrylate ester fuming (CEF) was implemented for all exhibit types, with the addition of physical developer (magnetic powder) on leaves and feathers (chapter 4). The adhesion of the physical developer was consistent throughout feathers, and green leaves, but varying results were obtained from brown leaves. The overall recovery types chosen were lifting (J-lar tape lift and gel lift), and casting (Provil and resin), with varying results being obtained both in terms of ridge detail recovered, as well as damage caused to the exhibit. CEF development on anti-climb paint produced robust fingermarks and was therefore suitable for casting, due to the presence of three-dimensional features (chapter 3). Casting methods captured a good level of ridge detail, with a small number of limitations, primarily caused by the quality of the original fingerprint deposit. Recovery techniques proposed within this work allow for preservation of ridge detail on a surface previously considered difficult in practice