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Tape is a type of trace evidence commonly seen in forensic science. Little to no research has been published regarding the optimal storage material for pressure-sensitive adhesive (PSA) tape. The purpose of this project was to determine the substrate with the least amount of interference for storing PSA tape. Interferences such as difficulty removing tape from the substrate or substrate components leaching into the adhesive can affect the analysis. This was a long-term study in which samples were stored on various substrates for nearly 10 years. Ten different tape samples were placed on eight different substrates for a total of 80 samples. The substrates included typical materials currently used for tape storage as well as other, less common materials. The tape samples were evaluated for ease of removal at various time intervals. The adhesives from each tape were analyzed at similar time intervals by Fourier transform infrared spectroscopy (FTIR). In addition, the adhesives were analyzed by pyrolysis gas chromatography-mass spectrometry (PyGC-MS), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and x-ray fluorescence (XRF) at the last time interval (112 months) and compared to the adhesive tape samples from the original rolls of tape to determine if there was any adverse effect from the substrates during storage. The FedEx backing was the only substrate that had no adverse effects regarding ease of removal. The substrates that had the least effect on the adhesive for both short-term and long-term storage included FedEx backings, adhesive sheet backings, and polyester transparency sheets.

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Fingernails can act as important forensic evidence as they can be a source of DNA that may link the victim or accused to the crime scene and may also contain traces of drugs such as cocaine and heroin, in regular users. Moreover, previous studies have shown that analyzing fingernails with various techniques can reveal important information, such as age and sex. In this work, ATR-FTIR spectroscopy with chemometric tools has been used to estimate the age and sex from fingernails by analyzing 140 fingernail samples (70 males, and 70 females) collected from volunteers aged between 10 and 70 years old. The amide bands obtained from spectra confirmed the presence of keratin proteins in the samples. PCA and PLS-R were used for the classification of samples. For sex estimation, samples were divided into four categories based on age groups, followed by the differentiation of sex in each group. Similarly, for age estimation, all samples were divided into two sets based on male and female followed by differentiation of age groups in each set. The result showed that PLS-R was able to differentiate fingernail samples based on sex in groups G1, G2, G3, and G4 with R-square values of 0.972, 0.993, 0.991, and 0.996, respectively, and based on age in females, and males with R-square values of 0.93 and 0.97, respectively. External validation and blind tests were also performed which showed results with 100% accuracy. This approach has proved to be effective for the estimation of sex and age from fingernail samples.

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The evaluation of the results from a fibre comparison given activity level propositions is well established when considering only a single group of potential primary transfers. However, secondary transfers are less prevalent in the literature despite their potential value, especially in cases where the primary transfers are not sufficiently informative. In particular, one can consider the fibres from frequented environments of the person of interest (POI) identified in a struggle. If the POI did struggle with the complainant, these fibres can potentially be recovered in small quantities on the surface of the complainant as a result of secondary or higher order transfers. Therefore, these fibres may provide useful information that can resolve competing propositions involving struggles, as well as forensic intelligence in the form of linkages or investigative leads. If a non-differentiation is indeed found between recovered fibres and fibres from the frequented environments of the POI, these results need to be properly interpreted. In this paper, a model, based on an object oriented Bayesian network (OOBN), for evaluating such findings along with its implementation is proposed. Using available data from the literature and other sources, the model was then used to assess a few hypothetical scenarios involving secondary transfers. The results provided useful insights into secondary transfer that help to validate the model and demonstrate the potential utility that can be gained by considering transfers beyond the primary order. Moreover, these results can be used to help guide future research by identifying gaps in the literature. Finally, the direct application to a case study was conducted to demonstrate the practical aspects of such a model.

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Fluorescence spectroscopy is an attractive candidate for analyzing samples of nylon. Impurities within the polymers formed during the synthesis and processing of nylons give rise to the observed fluorescence, allowing for nylons to be analyzed based on their impurities. Nylons from the same source are expected to display similar fluorescence profiles, and nylons with different fluorescence are expected to be from different sources. This paper investigates an important case where different nylons displayed similar fluorescence, preventing easy discrimination. Samples of Nylon 6 and Nylon 6/12 had visually indistinguishable excitation-emission matrices (EEM), excitation spectra, fluorescence spectra, and synchronous fluorescence spectra at larger Δλ. By collecting synchronous fluorescence spectra at smaller Δλ, additional features in the fluorescence profiles were identified that allowed for some discrimination between the two nylons. Combining the EEM and synchronous fluorescence data with chemometric algorithms provided a clearer differentiation between the two nylons. parallel factor analysis, principal component analysis, and common dimension partial least squares (ComDim-PLS) showed two distinct clusters in the data, with ComDim-PLS providing the greatest distinction between the clusters. The loadings revealed the variables of interest to the ComDim-PLS were the 400 nm and 335 nm bands for all synchronous fluorescence spectra, the 460 nm and 310 nm bands for the Δλ = 20 nm and Δλ = 30 nm synchronous fluorescence spectra, and the 440 nm band for the Δλ = 20 nm synchronous fluorescence spectra. The linear discriminant analysis performed with the PLS data yielded a classification accuracy of 95% with the EEM data and 100% with the synchronous fluorescence data, displaying the power of this technique to differentiate two different nylons with visually indistinguishable fluorescence spectra.

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This paper introduces the concept of an operational reference glass database, specifically designed for broken glass fragments from ATM attacks, jewelry store robberies, and ramraids on high-end clothing stores. The database, initiated in 2014, is used to compare glass traces from organized crews involved said criminal activities. Utilizing LA-ICPMS, this study establishes a methodology for collecting reference glass samples from the scenes of the aforementioned crimes, thus creating a comprehensive database containing over 3500 reference glass samples from crime scenes. The operational database is employed to match trace elemental profiles of glass fragments from suspected items to known reference samples, offering specificity and accuracy. Analysis of results, while ongoing due to the nature of active cases, find matches of trace materials in over 50 % of case requests since 2019. Challenges such as database scalability and continuous updating are acknowledged, and future directions include technological advancements to enhance precision and the application into other areas of forensic material analysis. The paper emphasizes the efficacy of this specialized approach in chemical profiling, providing a potent tool for linking glass traces to specific criminal contexts and providing intelligence and investigative leads into individuals involved in ATM-related crimes.

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Deceased human remains are often buried as a forensic countermeasure or method of disposal by homicide perpetrators. Owing to this, the excavation of clandestine grave sites is a task that forensic crime scene teams may only encounter a few times a year. Not all crime scene units have specialised teams for this task, and even those that do, may not have specific protocols for the optimal recovery of forensic traces retained within grave fill as procedures such as sieving require optimisation for the specific soil conditions of the jurisdiction. This study aimed to define the optimal sieving conditions for a sandy environment when searching for minute traces of paint, glass, hair and fibres. Furthermore, this study justifies the practice of retaining grave fill and examining it under controlled laboratory conditions, rather than in-situ adjacent to the grave site. The results demonstrate that using sieve mesh sizes as fine as 0.1 mm can recover up to 82% of the deposited traces and almost all paint, hair and glass traces. The processing of grave fill in the laboratory lead to increased yield of forensic evidence, which on a case-basis may warrant the increased time needed. These findings merit consideration for clandestine grave crime scenes where evidence is scarce or the case is likely to become cold.

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DNA analysis of traces from commonly found objects like knives, smartphones, tapes and garbage bags related to crime in aquatic environments is challenging for forensic DNA laboratories. The amount of recovered DNA may be affected by the water environment, time in the water, method for recovery, transport and storage routines of the objects before the objects arrive in the laboratory. The present study evaluated the effect of four storage conditions on the DNA retrieved from bloodstains, touch DNA, fingerprints and hairs, initially deposited on knives, smartphones, packing tapes, duct tapes and garbage bags, and submerged in lake water for three time periods. After retrieval, the objects were stored either through air-drying at room temperature, freezing at -30 °C, in nitrogen gas or in lake water. The results showed that the submersion time strongly influenced the amount and degradation of DNA, especially after the longest submersion time (21 days). A significant variation was observed in success for STR profiling, while mtDNA profiling was less affected by the submersion time interval and storage conditions. This study illustrates that retrieval from water as soon as possible and immediate storage through air-drying or freezing before DNA analysis is beneficial for the outcome of DNA profiling in crime scene investigations.

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Trace evidence, including hair, fibers, soil/dust, and gunshot residue (GSR), can be recovered from a crime scene to help identify or associate a suspect with illegal activities via physical, chemical, and biological testing. Vacuum collection is one technique that is employed in recovering such trace evidence but is often done so in a targeted manner, leaving other complementary, chemical-specific information unexamined. Here, we describe a modified 3D-printed cone spray ionization (3D-PCSI) source with integrated vacuum collection for on-site, forensic evidence screening, allowing the processing of targeted physical traces and nontargeted chemical species alike. The reported form factor allows sample collection, onboard extraction, filtration, and spray-based ionization in a singular vessel with minimal handling of evidence by the operator. Utilizing authentic forensic evidence types and portable MS instrumentation, this new method was characterized through systematic studies that replicate CSI applications. Reliability in the form of false positive/negative response rates was determined from a modest, user-blinded data set, and other attributes, such as collection efficacy and detection limit, were examined.

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Solution dyed fibers are synthetic fibers colored through the addition of insoluble pigmentation to the polymer prior to extrusion. This is in contrast to most textile fibers, which are traditionally colored via immersion in liquid dyebaths following extrusion. Solution dyed fibers are increasing in market share in numerous applications (e.g., apparel, carpet, upholstery), and thus, the microscopic characteristics and variety of pigments used to color them represent unexploited properties in forensic fiber comparisons. This paper presents the development of a microscopical process to first recognize a fiber as solution dyed and subsequently characterize the color and optical properties of each type of pigment found in a given fiber. To this end, a set of 76 fibers, representing polypropylene, nylon, polyester, and rayon, spanning all nominal colors and several consumer applications were analyzed longitudinally and in cross section using a combination of polarized light, fluorescence, and oil immersion microscopy. A given fiber contained between one and six different pigments, and a total of 260 pigments (not all unique) were recognized within this set of fibers. Pigment morphologies were categorized as angular, elongated, rounded, finely divided, or streaky, and about 40% of the pigments fluoresced. Ultimately, this body of data is intended to provide trace evidence examiners with a specific approach to recognize and begin to exploit pigmented fibers encountered in casework.

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In cases where the suspected cause of death is smothering, fibre traces recovered from the nasal cavity are hypothesised to refute or support this proposition. In order to carry out such evaluations, an efficient recovery method must first be established. This pilot study tested five different recovery methods on 3D printed models of nasal cavities. Among which, the use of the transparent AccuTrans® polyvinyl Siloxane casts demonstrated the best recovery efficiency with a median of 90% of deposited fibres recovered. The efficacy of this method was then verified on cadavers. Apart from a reliable recovery method, an understanding of the background population of fibres in nasal cavities, as well as the mechanisms of the transfer from the purported smothering textile to the nasal cavity is essential to evaluate the findings in these cases of suspected smothering. Samplings of the nasal cavities of 20 cadavers were thus carried out to gather data on the background population of fibres. Results showed that nasal cavities are not void of fibres, but the quantities are expected to be low, with a mean of 3.8 fibres per cavity recovered. Information on generic fibre class, colour, and length of these background fibres were also obtained with the use of low and high-power microscopy. The frequencies found in this population of fibres closely align with data from other population studies where black cotton was the most common. Finally, transfer experiments using the 3D printed models fitted with a respiratory pump to simulate breathing were carried out, along with testing on live volunteers in-vivo. The results demonstrated a verifiable transfer of fibres into the nasal cavity in smothering scenarios. Textiles of various shedding capacities were used in these tests and the findings suggest an influence of this variable on the quantities of fibres transferred.

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As workers in medicine, food science, and advanced manufacturing have learned, pristine disposable gloves are an innate source of chemical contamination from the moment they are first donned. Given the typically low extent of chemical contamination on the surface of gloves post-manufacture, many fields overlook, or simply discount, this source of transferable chemical evidence. However, forensic science should not adopt this approach. Instead, the trace chemical signatures left after handling objects while wearing different brands and types of disposable gloves could provide new avenues of forensic intelligence when assessing crime scenes. Similarly, an appreciation of the potential for disposable gloves to transfer innate chemical residues is an important consideration when surface analyses of evidence are envisioned. This review summarises past reports of chemical transference originating from pristine gloves drawn from the fields of medicine, food science, and material science, as well as the few examples highlighting the implications of such events for forensic investigations. Correlations between the chemical identities of the contaminants and the material of glove manufacture are provided here where known, with energy-intensive chemical extraction of glove material, and passive transference of chemical residues through simple contact, both explored. Finally, discussions pertaining to the implications of disposable glove residues, coupled with opportunities for future research, are outlined.

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A new method to determine the make and model of a vehicle from an automotive paint sample recovered at the crime scene of a vehicle-related fatality such as a hit-and-run using Raman microscopy has been developed. Raman spectra were collected from 118 automotive paint samples from six General Motors (GM) vehicle assembly plants to investigate the discrimination power of Raman spectroscopy for automotive clearcoats using a genetic algorithm for pattern recognition that incorporates model inference and sample error in the variable selection process. Each vehicle assembly plant pertained to a specific vehicle model. The spectral region between 1802 and 697 cm-1 was found to be supportive of the discrimination of these six GM assembly plants. By comparison, only one of the six automotive assembly plants could be differentiated from the other five assembly plants using Fourier transform infrared spectroscopy (FT-IR), which is the most widely used analytical method for the examination of automotive paint) and the genetic algorithm for pattern recognition. The results of this study indicate that Raman spectroscopy in combination with pattern recognition methods offers distinct advantages over FT-IR for the identification and discrimination of automotive clearcoats.

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Glass fragments are often recovered from garments worn by the authors of certain types of crimes and are useful as they present strong connections to the scene at both the source and activity level. It is known that the transfer of glass fragments is impacted when recipient garments are dampened, such as by rain, however, the details of the effect are not clear. This research aimed to determine the impact of substrate dampness on glass retention. Across the three test garments, a cotton t-shirt was found to increase in retentiveness with increasing dampness, while a wool/polyester blend jumper and a cotton hoodie were both found to increase only to a point, before decreasing again when the garment was saturated. This is attributed to the construction of the fabrics, as it does not appear to be related to the identity of the textile itself. It was also found that the size distribution of fragments changed with dampness. All the garments retained a smaller proportion of fragments less than 0.5 mm in size when saturated or dampened than when dry, along with an increase in the proportion of fragments in the 1-1.5 mm and greater than 1.5 mm size categories. These results indicate that is important to consider the impact of substrate dampening when relevant, and that this consideration must be done holistically as different substrates respond to dampening in different ways. It also indicates that consideration of the size distribution in fragment populations may reveal additional information in complex scenarios.

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BACKGROUND: Forensic Microbiology is an emerging branch of science that has great potential to assist criminal investigations. Having said that, microbial analysis is not performed routinely during forensic investigations in India. This could be attributed to lack of specific training and lack of evidence-based standard protocol. OBJECTIVES: The authors attempt to highlight the key areas in forensic microbiology that need to be explored in a developing nation like India. CONTENT: Forensic microbiology could help in linking a person to a crime, determining the cause of death, estimating postmortem interval (PMI), etc. Additionally, applications are being developed by forensic microbiologists across the globe to investigate the coordinated and dynamic changes in microbial activity which occur after the death of a human host. Such evidence from the human postmortem microbiome can aid in criminal investigations and administration of justice. These recent advances and developments have the potential to transform the field of forensic microbiology in a developing country.

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The presence of diatom algae in bone marrow has been used as forensic evidence of drowning for several decades; however, these studies are based on known or suspected recent drowning events. This study addresses the potential for diatoms to enter the bone marrow of skeletal remains, that is, de-fleshed long bones post-mortem. In laboratory and field experiments, bones were either inflicted with two access points by a cut and acid pitting or left intact. The bones were submerged in water for at least 1 week and up to 3 months. Samples of the bone surface and marrow were inspected for diatoms. The analysis considered the time required for diatoms to enter marrow and whether genus characteristics like size or mobility affect entry. The presence of an access point influenced diatom entry in that bones without an introduced access point had zero to one diatom present in the marrow, whereas a bone with an access point had >150 diatoms present in the marrow. The results of both laboratory and field phases suggest that diatoms will reliably colonize bone in as quickly as 1 week, establishing and maintaining communities for at least 3 months. However, the bone surface assemblages differ from the source community. Bone marrow displayed even more restrictive access to diatom colonization, resulting in communities dominated by small raphid diatoms. Based on these findings, we suggest some caveats on the use of diatoms as trace evidence in forensic science with recommendations for future avenues of research.

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Diatoms show potential as trace evidence indicators, particularly as evidence of drowning. Often, the diatom test to diagnose drowning is done on soft tissue or bone marrow from a recently deceased individual. This method presented here combines elements from previous forensic literature and methods of diatom isolation in phycology to extract diatoms from bone marrow of skeletal remains for forensic use. This diatom extraction method is time-efficient, minimizes contamination risk, and produces samples of intact diatoms. This method is designed to complete sample preparation within 24 h, sampling the bone for diatoms internally and externally. This method was developed using porcine long bones submerged in water with live diatoms for up to 3 months. Three marrow samples were extracted from each bone so the method was developed using 102 marrow samples. Additionally, 132 surficial bone and environmental samples were collected and prepared during method development. To briefly summarize the method, the bone joints were cut off with an angle grinder in a biosafety hood to expose the marrow, which was removed from the hip, knee, and shaft as separate samples. The marrow was digested with nitric acid at 400°C in glass beakers before being centrifuged with DI water, plated onto microscope slides, and observed with a compound microscope. Observation found good preservation of unbroken diatom cell walls throughout the process. This method can be used to prepare diatoms as forensic trace evidence.

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Environmental trace evidence offers useful circumstantial intelligence to link persons and scenes of forensic interest. An increasing empirical research base is dedicated towards understanding the transfer and persistence dynamics of environmental indicators including pollen, soils, and diatoms, within a diverse range of experimental frameworks. This paper presents two discrete studies exploring transfer and persistence of soils and sediments on footwear and diatomaceous earth adhered to clothing in forensically pertinent scenarios. Variables including sediment type, foot position, clothing type, and body positioning were also explored throughout. Both experiments incorporated a field-based methodology during the sampling effort. Photographs were collected of an initial transfer sample and of a retained assemblage following hours, days, and up to one-week of wear, facilitating macroscopic assessment of trace evidence dynamics. All images were processed using accessible, open-source software before spatial analysis of evidence distribution within and temporal assessment (% retention) upon each evidential surface. The results highlighted consistent loss of transferred sediment from footwear with significantly greater retention of loamy clay soil than dune sand which was absent beyond 24 h of wear. Loss was not influenced by wearer gait but was more rapid from those areas of the shoe sole in direct contact with the ground. Diatomaceous earth was retrieved from all three clothing types tested after one week - significant losses of material occurred before 48 h with a consistent assemblage identified beyond this. Denim was significantly more effective than acrylic and fleece for diatomaceous earth retention and significantly more material was lost from clothing worn on the lower body. These findings highlight the value of using visual environmental markers and a macroscopic analytical approach during the investigation of environmental trace dynamics. The methodology offers a novel, non-destructive assessment of soil and diatom transfer and persistence, complementing more extensive laboratory-based examinations to ensure the development of a well-rounded research base within the forensic sciences.

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The increase in the number of fatal electric accidents over the years has escalated the demand for specialized forensic engineers to determine their relevant technical causes. Likewise, the complexities associated with identifying the causes of electrocution accidents have prompted the General Department of Forensic Science and Criminology at Dubai Police to adopt a new methodology to diagnose electrocution accidents, consisting of an approach that involves medico-legal examination, electrical diagnosis of the evidence, and trace evidence analysis. This paper will discuss the application of the adopted method in further detail by unfolding two case reports. The first report outlines a case in which a worker got electrocuted at a construction site while attempting to turn on a lamp. The second case report involves the death of a technician in a workshop after trying to disconnect a washing machine from its plug. The methodology was utilized during the investigation of both cases, which were attended by the appointed forensic engineers and showed promising results.

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Environmental DNA (eDNA), elemental and mineralogical analyses of soil have been shown to be specific to their source material, prompting consideration of using the airborne fraction of soil (dust) for forensic intelligence work. Dust is ubiquitous in the environment and is easily transferred to items belonging to a person of interest, making dust analysis an ideal tool in forensic casework. The advent of Massive Parallel Sequencing technologies means metabarcoding of eDNA can uncover bacterial, fungal, and even plant genetic fingerprints in dust particles. Combining this with elemental and mineralogical compositions offers multiple, complementary lines of evidence for tracing the origin of an unknown dust sample. This is particularly pertinent when recovering dust from a person of interest to ascertain where they may have travelled. Prior to proposing dust as a forensic trace material, however, the optimum sampling protocols and detection limits need to be established to place parameters around its utility in this context. We tested several approaches to collecting dust from different materials and determined the lowest quantity of dust that could be analysed for eDNA, elemental composition and mineralogy, whilst still yielding results capable of distinguishing between sites. We found that fungal eDNA profiles could be obtained from multiple sample types and that tape lifts were the optimum collection method for discriminating between sites. We successfully recovered both fungal and bacterial eDNA profiles down to 3 mg of dust (the lowest tested quantity) and recovered elemental and mineralogical compositions for all tested sample quantities. We show that dust can be reliably recovered from different sample types, using different sampling techniques, and that fungi and bacteria, as well as elemental and mineralogical profiles, can be generated from small sample quantities, highlighting the utility of dust for forensic intelligence.

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