Refining Fingermark Development using Diacetylene Copolymers on Difficult Surfaces,

In further work investigating the intriguing application of diacetylene copolymers in fingermark detection, methods were developed to control (inhibit or enhance) the diacetylene polymerization reaction in fingermarks treated with a mixture of the monomers 2,4‐hexadiyne‐1,6‐bis‐(phenylurethane) (HDDPU) and 2,4‐hexadiyne‐1,6‐bis(p‐chlorophenylurethane) (HDDCPU) in acetone solution. These methods included the use of a humidity chamber to reduce the amount of background development while promoting development on the fingermark, subjecting developed fingermarks to freezing temperatures and using a solvent to remove unreacted monomer in order to inhibit the polymerization reaction. Developed fingermarks were enhanced by conventional lighting (white light, filtered light) and fast Raman mapping, which was shown to be advantageous over FTIR imaging. This study also demonstrated the applicability of diacetylene copolymer solutions in the covert detection of fingermarks on difficult surfaces. Furthermore, fingermarks were successfully developed with good ridge detail on pig skin (used as a model for human skin, a notoriously difficult surface on which to develop fingermarks).     

Introducing a semi-automatic method to simulate large numbers of forensic fingermarks for research on fingerprint identification

Statistical research on fingerprint identification and the testing of automated fingerprint identification system (AFIS) performances require large numbers of forensic fingermarks. These fingermarks are rarely available. This study presents a semi-automatic method to create simulated fingermarks in large quantities that model minutiae features or images of forensic fingermarks. This method takes into account several aspects contributing to the variability of forensic fingermarks such as the number of minutiae, the finger region, and the elastic deformation of the skin. To investigate the applicability of the simulated fingermarks, fingermarks have been simulated with 5-12 minutiae originating from different finger regions for six fingers. An AFIS matching algorithm was used to obtain similarity scores for comparisons between the minutiae configurations of fingerprints and the minutiae configurations of simulated and forensic fingermarks. The results showed similar scores for both types of fingermarks suggesting that the simulated fingermarks are good substitutes for forensic fingermarks.     

A Preliminary Study on Vacuum Metal Deposition as a Standalone Method for Enhancement of Fingermarks on Ballistic Brass Materials

In order to assess the efficacy of vacuum metal deposition (VMD) as a technique to develop fingermarks on ballistic metallic surfaces, a preliminary study using six donors (three male & three female) was conducted. Using a sequential metal deposition process, two metal combinations were studied—gold/zinc and silver/zinc. Results indicate the potential of this technique, by developing identifiable fingermarks on brass metal disks aged from a few days up to more than a month old. As the development of fingermarks on fired (brass) cartridge cases is an area of interest, a further study was conducted where a total of 20 fingermarks were deposited on cases. After firing, second level fingermark characteristics were successfully observed on cartridge cases highlighting its potential as a fingermark enhancement method for ballistic brass materials. Further work is required to fully evaluate the VMD process and its reliability as a fingermark enhancing method on ballistic surfaces.     

Sex determination from hand and foot bone lengths

Numerous studies have addressed sex estimation from the hands and feet with varying results. These studies have utilized multiple measurements to determine sex from the hands and feet, including measures of robusticity (e.g., base width and midshaft diameter). However, robusticity measurements are affected by activity, which can disguise underlying patterns of sexual dimorphism. The purpose of this study is to investigate the utility of length measurements of the hands and feet to estimate sex. The sample consists of white females (n=123) and males (n=136) from the Terry Collection. Discriminant function analysis was used to classify individuals by sex. The left hand outperformed both the right hand and foot producing correct classification rates exceeding 80%. Surprisingly, the phalanges were better sex discriminators than either the metacarpals or metatarsals. This study suggests that length measures are more appropriate than robusticity measures for sex estimation.     

Enhanced Visualization of Latent Fingermarks on Rough Aluminum Surfaces Using Sequential Au and Zn/ZnS/ZnO Depositions

Detection and visualization of fingermarks on rough and diffuse surfaces is a relatively challenging task. We succeeded in developing latent fingermarks on scratched and rough aluminum surfaces by sequential deposition of a thin layer of gold followed by one of zinc or zinc‐based compounds on the fingermarks. The best image enhancement was achieved with sequential Au and ZnS depositions. Using this combination, we could enhance the visualization of latent fingermarks aged over 65 days in normal conditions. The optical reflectance from the fingermarks with the deposited layers of metal/dielectric is analyzed as a stratified medium. Significant contrast in the reflectance from the regions of the ridges and the valleys of the fingermark would enhance the visualization. Our results show that the Au and ZnS bi‐layer combination can have a large reflection contrast and improved fingermark visualization at wavelengths corresponding to the green light for specific thickness of ZnS.     

Identification of a Suspect in a Murder Case through Recovery of Fingermarks from a Fired Cartridge Case

During the period of one year, the Police of the State of Espírito Santo in Brazil analyzed 1,431 cartridge cases obtained from crime scenes and seizures. The cartridges were subjected to a development sequence (cyanoacrylate fuming + gun bluing + fluorescent dying), and panoramic images of the developed fingermarks were generated based on the photographs taken during the rotation of the cartridges. Ridge details were observed in 50 cartridges, but only in 5 cartridges, the marks were considered with value for identification. The fingermarks were searched in the Automated Fingerprint Identification System (AFIS) of the Brazilian Federal Police and, in one case, it was possible to obtain the suspect's identification. In our knowledge, this is the first case in Brazil of identification of a suspect based on a fingermark recovered from a fired cartridge case.     

The Effect of pH on Electrolyte Detection of Fingermarks on Cartridge Cases and Subsequent Microscopic Examination

Cartridge cases may contain deposited fingermarks when the firearm was loaded ( http://www.nij.gov/pubs-sum/225320.htm , J Forensic Sci, 53 , 2008 and 812). Cartridge cases can be individualized with microscopic examination. However, heat and friction degrades the deposited fingermark on the fired cartridge cases, if any on the surface. Also, unfired and fired cartridge cases are made of metal, which is a nonporous surface that does not retain fingermarks well ( http://www.nij.gov/pubs-sum/225320.htm ). This study tests the effects of pH level on fingermark clarity on brass fired and unfired cartridge cases and microscopic striation examination (MSE). Two trials were performed to determine the optimal pH in fingermark clarity for both types of cartridges. This was performed through immersion in six pH range solutions from dilutions of sulfuric acid and sodium hydroxide for 24 h for the purpose of enhancing the fingermarks on the metal. The use of the optimal neutral pH level is suggested because immersion of the cartridge cases in pH 1–3 and 3–5 affects MSE.     

Exposing latent fingermarks on problematic metal surfaces using time of flight secondary ion mass spectroscopy

Fingermarks are a key form of physical evidence for identifying persons of interest and linking them to the scene of a crime. Visualising latent (hidden) fingermarks can be difficult and the correct choice of techniques is essential to develop and preserve any fingermarks or other (e.g. DNA) evidence that might be present. Metal surfaces (stainless steel in particular) have proven to be challenging substrates from which to reliably obtain fingermarks. This is a great cause for concern among police forces around the globe as many of the firearms, knives and other metal weapons used in violent crime are potentially valuable sources of fingermark evidence. In this study, a highly sensitive and non-destructive surface science technique called time of flight secondary ion mass spectroscopy (ToF-SIMS) was used to image fingermarks on metal surfaces. This technique was compared to a conventional superglue based fuming technique that was accompanied by a series of contrast enhancing dyes (basic yellow 40 (BY40), crystal violet (CV) and sudan black (SB)) on three different metal surfaces. The conventional techniques showed little to no evidence of fingermarks being present on the metal surfaces after a few days. However, ToF-SIMS revealed fingermarks on the same and similar substrates with an exceptional level of detail. The ToF-SIMS images demonstrated clear ridge definition as well as detail about sweat pore position and shape. All structures were found to persist for over 26?days after deposition when the samples were stored under ambient conditions.     

Fingermark Evidence Evaluation Based on Automated Fingerprint Identification System Matching Scores: The Effect of Different Types of Conditioning on Likelihood Ratios

In recent studies, the evidential value of the similarity of minutiae configurations of fingermarks and fingerprints, for example expressed by automated fingerprint identification systems (AFIS), is determined by likelihood ratios (LRs). The paper explores whether there is an effect on LRs if conditioning takes place on specified fingers, fingerprints, or fingermarks under competing hypotheses: In addition, an approach is explored where conditioning is asymmetric. Comparisons between fingerprints and simulated fingermarks with eight minutiae are performed to produce similarity score distributions for each type of conditioning, given a fixed AFIS matching algorithm. Both similarity scores and LRs are significantly different if the conditioning changes. Given a common‐source scenario, “LRs” resulting from asymmetric conditioning are on average higher. The difference may reach a factor of 2000. As conditioning on a suspect's finger(print) is labor‐intensive and requires a cooperating suspect, it is recommended to just condition on the number of minutiae in the fingermark.     

Fixing Transient Iodine on Developed Latent Fingermarks

In the present study, a simple and novel fume–mist technique is described which can be used efficiently to fix the latent fingermarks developed using iodine. It is well known that the residues left over in the fingermarks interact with iodine to give transient brown impressions which disappear in a short time. Also, iodine forms colored complexes with various organic solvents. Based on iodine–fingermark interaction and iodine–solvent complex formation, latent fingermarks were developed on paper surface using iodine fumes which were subsequently fixed by spraying polar and nonpolar solvents. The fingermarks developed with this technique were not only clear but also permanent in nature. The interaction of fingermark residue, iodine, and solvent forming a ternary structure is believed to be a possible reason for the stability of iodine‐developed fingermarks. Ease of method, availability of chemicals, and minimum training make the method adaptable in routine development of forensic fingermarks present on paper surface.     

Ninhydrin Thiohemiketals: Basic Research Towards Improved Fingermark Detection Techniques Employing Nano‐Technology*

Abstract: In the first part of a comprehensive research project towards more efficient application of nano‐technology to fingerprint visualization, we investigated the possibility of more selective binding of gold nanoparticles (NP) to fingerprint material. We synthesized derivatives of ninhydrin and 1,2‐indanedione containing loosely bound thiol groups. In particular: thiohemiketals (THK) of ninhydrin, and thioketals of 1,2‐indanedione were prepared and tested as potential fingerprint reagents. By reacting ninhydrin with various thiols we were able to produce a series of novel THK, bearing the SR group always at C2. Ninhydrin THK reacted with amino acids to produce the expected Ruhemann’s purple, and they also developed latent fingermarks on paper in a similar manner to ninhydrin. Ketals and thioketals derived from 1,2‐indanedione reacted neither with amino acids nor with latent fingermarks. In the second part of the research, the thiols which are formed on the ridges as byproducts of the reaction with amino acids will be tested for their potential as stabilizers for gold NP that will become covalently bound to the fingerprint ridges.     

The potential (negative) influence of observational biases at the analysis stage of fingermark individualisation

Recent cases of erroneous identification have strengthened critical comments on the reliability of fingerprint identification. This goes hand in hand with recent publications regarding the lack of scientific foundation of the discipline. Combined with "legislative" needs, such as for instance the admissibility criteria under Daubert, or experimental studies revealing potential bias, the call for research on the identification process has become more urgent. That background set the basis of this research project financed by the Swiss National Science Foundation (SNSF) which includes, among other parts, experimental tests to study potential observational biases in the analysis stage of fingerprint individualisation. These tests have been submitted to several groups of forensic science students at the University of Lausanne. The aim is to study factors potentially influencing the analysis of fingermarks, more specifically the influence of training/education (test I) as well as the potential impact of case contextual information or known print availability (test II). For all tests students were given 11 or 12 fingermarks of a medium to difficult quality, with a range of 8-15 minutiae. For all tests the task was always the same for the participants but carried out in different contexts: to analyse the marks, to annotate the minutiae observed, to designate them and to decide on the status of the mark in two categories, exploitable and identifiable. The aim was to see how the fingermarks were annotated by different individuals so as to have an idea of the variation in annotation and counting in the analysis stage only. For test I, students were submitted the same 12 fingerprints before and after having followed specific training in fingermark individualisation. The aim was to see how training/education impacts the analysis of fingermarks. For test II, were participants given eleven fingermarks so as to study whether the presence of a comparison print changes the amount of minutiae found and whether low/high-profile background information influences the analysis stage. Results show that for test I the effect of training can be observed, among other, in an increase of minutiae annotated and a higher consensus between participants. For test II no effect of the stimuli used to induce observational biases has been observed by all of the factors studied.     

Self‐Strangulation Turning into Partial Hanging for a Suicide Victim

Hanging is the most common asphyxial method of suicide, whereas suicide by strangulation is unusual. Here, we are reporting a particular methodology of the asphyxial method of suicide in which a case of self‐strangulation culminated into partial hanging. A 30‐year‐old male wrapped one end of the cable wire around his neck. He then passed the other end over a curtain rod and tied that end around the right hand. He pulled the hand down, using the curtain rod as a fulcrum, to tighten the noose around the neck in an attempt to strangulate himself. However, he lost consciousness during the process and the body slipped down, pulling the right hand up which got stuck at the curtain rod. This led the body hanged in the kneeling position. This bizarre scenario raised suspicion of homicide but the crime scene, autopsy and victim characteristics were in favor of suicide.     

Development of Latent Fingermarks on Various Surfaces Using ZnO‐SiO2 Nanopowder

Fingermarks are one of the most useful forms of evidence in identification and can provide generalized proof of identity in crime investigation. They are developed using various conventional powders. The novel nanopowder ZnO‐SiO₂ was synthesized via the conventional heating method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy‐dispersive X‐ray (EDX) analysis, transmission electron microscope (TEM), and X‐ray diffraction (XRD). The mean particle size of ZnO‐SiO₂ nanopowder calculated through TEM was 32.9 nm. The development of fingermarks was carried out by powder dusting and small particle reagent (SPR) methods. Powder dusting method was used for the development of latent fingermarks on various dry, nonporous, and semi‐porous surfaces. The SPR method was also applied to wet nonporous surface. The developed latent fingermarks using ZnO‐SiO₂ nanopowder were found to have excellent quality with very clear third‐level ridges detail and had better visibility than commercially available white powder.     

Comparison of the Columnar‐Thin‐Film and Vacuum‐Metal‐Deposition Techniques to Develop Sebaceous Fingermarks on Nonporous Substrates,

Both the columnar‐thin‐film (CTF) and the vacuum‐metal‐deposition (VMD) techniques for visualizing sebaceous fingermarks require the deposition of a material thereon in a vacuum chamber. Despite that similarity, there are many differences between the two techniques. The film deposited with the CTF technique has a columnar morphology, but the film deposited with the VMD technique comprises discrete islands. A split‐print methodology on a variety of fingermarked substrates was used to determine that the CTF technique is superior for developing fingermarks on clear sandwich bags and partial bloody fingermarks on stainless steel. Both techniques are similar in their ability to develop fingermarks on glass but the CTF technique yields higher contrast. The VMD technique is superior for developing fingermarks on white grocery bags and the smooth side of Gloss Finish Scotch Multitask^? tape. Neither technique worked well for fingermarks on black garbage bags.     

Inherent Fluorescence Detection of Latent Fingermarks by Homemade Shortwave Ultraviolet Laser

Detection of latent fingermarks on various substrates is critical in crime investigations. Conventional chemical methods using reagents could contaminate or even destruct biological information of samples. Here, an optical method and successful case application of detecting latent fingermarks through long‐wave ultraviolet (UV) fluorescence (300–400 nm) by shortwave UV laser excitation is reported. Experimental results indicate that the recovery rate of the latent fingermarks on various paper items is in the range of 70–80% without chemical treatments. Moreover, the optical method allows for the preservation of samples for further examination, such as polymerase chain reaction (PCR) testing. The technique has also been successfully applied to a criminal case in identifying the suspect, which, to the best of our knowledge, has never been reported in real crime investigations. Therefore, such a method as UV‐excited UV fluorescence in detecting latent fingermarks may be better for examination in cases where biological information of samples is needed for consequent testing.     

Visualization of Fingermarks Deposits on Untreated Thermal Paper Exploiting the Near Infrared Luminescence

Thermal paper is widely used as a print medium for different applications but it constitutes a tricky substrate for fingermark visualization. An earlier work (J Forensic Sci 2015; 60 :1034) reported how to visualize fingermarks on untreated thermal paper by illuminating the item with a UV-A light source. In the present paper, the potential of the near infrared (NIR) luminescence has been tested on thermal paper compared to the mentioned method. A controlled study was carried out utilizing eccrine enriched fingermarks. The promising outcomes obtained were further confirmed by performing a pseudo-operational trial. Data clearly showed that the use of the NIR filter gave better results. Finally, preliminary tests suggested a different mechanism of reaction induced by fingermarks with respect to the one behind the thermal printing. Thus, NIR luminescence represents a refinement to the suite of optical examination processes, including the potential to increase the number of marks recovered in a noncontact, nondestructive way.     

Initial Results on the Composition of Fingerprints and its Evolution as a Functionof Time by GC/MS Analysis

Abstract: Determining the time since deposition of fingermarks may prove necessary to assess their relevance to criminal investigations. The crucial factor is the initial composition of fingermarks, because it represents the starting point of any aging model. This study mainly aimed to characterize the initial composition of fingerprints, which show a high variability between donors (inter‐variability), but also to investigate the variations among fingerprints from the same donor (intra‐variability). Solutions to reduce this initial variability using squalene and cholesterol as target compounds are proposed and should be further investigated. The influence of substrates was also evaluated, and the initial composition was observed to be larger on porous surface than nonporous surfaces. Preliminary aging of fingerprints over 30 days was finally studied on a porous and a nonporous substrate to evaluate the potential for dating of fingermarks. Squalene was observed to decrease in a faster rate on a nonporous substrate.     

Concealed homicidal strangulation by burning.

Compression of the neck, either with the hands or by a ligature, is not an uncommon method of homicide. Burning of the body to try to conceal the homicide may complicate the situation by making it difficult to interpret the findings. We hereby report two cases of homicidal ligature strangulation with extensive burning of the bodies. In both cases, external findings included the presence of a soft piece of fabric around the neck that, when removed, disclosed a portion of pale, unburned skin that vividly contrasted with surrounding areas. Osteocartilaginous lesions were present in only one case. Carboxyhemoglobin levels in both cases were very low, and the histopathologic examination of distal airways for soot particles was negative.     

The Compatibility of Fingerprint Visualization Techniques with Immunolabeling

The chemical composition of a fingermark potentially holds a wealth of information about the fingermark donor, which can be extracted by immunolabeling. Immunolabeling can be used to detect specific components in fingermarks; however, to be applicable in the forensic field, it should be compatible with commonly used fingerprint visualization techniques. In this study, the compatibility of immunolabeling with two different fingerprint visualization techniques, magnetic powdering and ninhydrin staining, was investigated on fingermarks deposited on glass and on nitrocellulose membranes. With dermcidin as antigen of interest, immunolabeling was performed successfully on all developed fingermarks. We can conclude that immunolabeling is compatible with magnetic powdering and ninhydrin staining, which can be of great forensic value.