The global transition toward trial-centered judicial systems demands unprecedented scientific objectivity and verifiability in forensic soil provenance. While emerging high-throughput analytical methodologies generate rich multi-modal datasets, extracting robust "electronic fingerprints" from these complex matrices remains a formidable challenge. Current chemometric applications are heavily hindered by severe multi-collinear redundancy and, more critically, the "algorithmic dependency trap", wherein the identified critical markers are heavily biased by the specific mathematical architecture of a chosen machine learning classifier. To overcome these limitations, this study introduces a two-stage feature distillation paradigm designed to eliminate algorithmic artifacts and extract resilient, mechanism-driven fingerprints. In the initial phase of coarse space sparsification, a Least Absolute Shrinkage and Selection Operator regularization scheme is executed under strict linear constraints to suppress multi-collinear noise and isolate a highly discriminative candidate subset. In the subsequent phase of fine cross-model distillation, this subset is exposed to a heterogeneous benchmarking suite of nine cutting-edge algorithms. By evaluating cross-model feature saliency convergence, we filter out mathematical biases and capture true algorithmic invariance markers. Remarkably, this distillation framework successfully decouples the convoluted soil matrix into a high-dimensional orthogonal geochemical fingerprint space governed by two consensus markers: titanium dioxide (TiO2) and silver (Ag). Geochemical interpretation confirms that the conservative, high-field-strength TiO2 functions as an immutable geological clock reflecting parental lithology and chemical weathering baselines, whereas the chalcophile element Ag acts as a sensitive tracker of localized metallogenic backgrounds and superimposed anthropogenic imprints. This orthogonal system achieves near-perfect classification fidelity with an Area Under the Curve (AUC) of 0.998 in cross-validation. By transitioning from empirical predictive modeling to robust feature distillation, this framework provides a low-cost, legally defensible, and mechanistically-grounded paradigm for soil evidence valuation that directly satisfies the stringent reproducibility demands of modern jurisprudence.

Industrial explosives are usually strictly controlled,with many sales links and high prices,which bring great profits to the homemade explosives.In recent years,cases of illegal manufacturing,trading,transportation and storage of ammonium nitrate explosives have frequently occurred.The raw materials for homemade ammonium nitrate explosives are widely available and easy to obtain.These result in the complex compositions and formulations.Accurate qualitative and quantitative characterization of its composition is of great significance for comparison,tracing and case investigation.Powder X-ray diffraction(PXRD)has become an efficient method to identify the component.However,it is still in the qualitative stage,i.e.matching of the phase and lack of quantitative method to illustrate the content of each substance in mixtures.In this paper,a quantitative method based on PXRD is described,including pre-processing method,sample preparation,instrument parameter settings and full spectrum fitting method.Firstly,the crystalline phase and amorphous phase components contained in the sample are accurately judged.Subsequently,Rietveld refinement method is used in which multi-dimensional factors such as structural parameters,peak parameters,instrument parameters are all included.The differences between the measured pattern and the calculated pattern is the target function and the optimization algorithm is used to obtain model parameter.After refinement fitting,the best structural parameters and other parameters including content of each component are all identified.The method can realize the quantitative characterization of powder,granular,or block solids.It can provide an important basis for the comparison and tracing of such evidences,so as to further correlate the cases.

Smokeless powder is the primary propellant in civilian and military ammunition, and in China, the use of propellants to make homemade ammunition and bombs is an emerging criminal practice. The identification and differentiation of the propellants used can provide forensic information about their sources. Depending upon the ammunition manufacturer and type, the recipe of propellants varies, and the characterization of smokeless powders in terms of their spectral components is useful for differentiating propellants. In this work, near-infrared spectroscopy (NIR) and chemometric modeling were used to explore the feasibility of differentiating and predicting smokeless powders from different sources. By comparison, the proposed neural network model in the study exhibited an average accuracy of over 80%. Furthermore, the potential for differentiating smokeless powders was well demonstrated via simple and rapid near-infrared spectroscopic analysis, and the employment of chemical agents and time-consuming chromatography and mass spectrometry could thereby be avoided.

The source inference of triacetone triperoxide (TATP) is of great significance in the fight against crime. Isotope ratio mass spectrometry (IRMS) is a reliable method for accurately measuring the isotope ratio, and it has been successfully used to differentiate and trace various explosives, including TATP. However, the current studies are not suitable for analyzing trace amounts of TATP in complex matrices. The matrix at the explosion site is complex, with severe interference and low levels of explosive residues, which makes it difficult to extract the explosive residues. Therefore, an effective method for extracting and enriching TATP is necessary before conducting IRMS analysis. Solid-phase microextraction (SPME) is an efficient extraction technology that combines extraction, concentration and sample injection. In this study, SPME-gas chromatography-isotope ratio mass spectrometry (GC-IRMS) method based on isoreticular metal-organic framework-8 (IRMOF-8) coated fiber was established for the first time for the analysis of δ13C and δ2H signatures of TATP. The limits of detection of δ13C and δ2H signatures of TATP were 100 ng and 9 µg, respectively, with measurement errors of 0.36 ‰ and -3.75 ‰. The IRMOF-8-coated fiber exhibited better mechanical stability and a lower limit of detection compared to the commercial polydimethylsiloxane (PDMS) fiber. Using the established method, six TATP samples from different sources were distinguished accurately. The impact of matrix (soil and tap water) on δ13C and δ2H signatures of TATP was also investigated. The established method demonstrated high sensitivity and precision, making it suitable for in-situ extraction and source of trace explosive residues in explosion cases.

The stable isotope analysis of black powder (BP) is of great significance for its comparison and source inference. Previous studies have verified the feasibility of distinguishing different BP samples through stable isotopes. However, the impact of raw materials and synthesis processes on the stable isotopes of BP remains unclear. On the one hand, the raw materials of BP are widely sourced, and whether stable isotopes can distinguish different source materials remains to be studied. On the other hand, the synthesis of BP involves the physical mixing of raw materials, and whether this process leads to isotope fractionation also needs further investigation. To address these problems, stable isotope ratios of 27 charcoals, 15 potassium nitrates, 6 self-made and 10 commercial BP samples were analyzed. The results showed that the stable isotope ratios can be utilized to distinguish charcoals and potassium nitrates from different manufacturers and batches. No significant differences in the nitrogen and oxygen stable isotope ratios between the self-made BP and its raw materials were observed, indicating that the physical mixing process does not induce significant fractionation of stable isotopes. However, the carbon stable isotope ratios of charcoal increased (within 2SD) after being synthesized into BP. Due to the utilization of additives and variations in the synthesis process, the correlation between the stable isotope ratios of commercial BP and its raw materials was complex. The findings of this study provide a scientific reference for tracing the source of BP.

In China, the use of smokeless powders for making homemade ammunition and bombs is an incipient criminal practice. One of the key tasks of analyzing smokeless powders in forensic sciences is to make comparisons between them, providing information about their source or establishing a link between two different smokeless powders seized at different locations. The main component of smokeless powders is nitrocellulose (NC) no matter what type of the smokeless powder is. As a kind of polymer, NC may have different molecular weights and polydispersity index (PDI) values, which could help the identification and differentiation of the smokeless powders. In this study, weight-average molecular weights (Mw), number-average molecular weights (Mn), and PDI value of 79 propellants samples from different sources were measured by gel permeation chromatography, and likelihood ratio evaluation method was applied to facilitate interpretation of the data. The possibility of using these methods to make comparisons between smokeless powders was explored instead of depending on analysis of target compounds with trace amounts in them.

Bacterial traceability refers to the use of a range of techniques to trace the origins and transmission pathways of bacteria. It is crucial in controlling the spread of diseases, analyzing bioterrorism incidents, and advancing microbial forensics. In recent years, the frequency and scope of bacterial outbreaks have continued to escalate, exerting significant impacts on global biosecurity, public health, and other areas. Consequently, it is required to process traceability of bacteria timely and accurately around the globe. The rapid development of biological and physicochemical traceability techniques provides convenience for tracing bacteria. These techniques not only surpass traditional methods in terms of sensitivity, traceability and throughput, but also find more extensive applications in elucidating bacterial growth mechanisms, transmission routes, and geographical origins. This paper systematically reviews the latest research progress and applications of technologies of bacterial traceability, highlighting key advancements and projecting future trends, with the intent of providing a valuable reference for researchers, facilitating further studies and innovations in this field.

In this paper, based on the high-frequency monitoring of current in the circuit via smart sockets and electrical situation data of the customer obtained, the current transition sequence and the univariate regression model for the feature of the current transition sequence are proposed. Based on the u03B5-fragment for the current steady sequence and fragment for the current stable sequence, a mining method for current transition sequence discovery is designed. And further, a univariate regression model is proposed to describe each current transition sequence. And with the univariate regression model, each current transition sequence in variable length is mapped into the feature space for the current transition sequence with fixed dimension. Furthermore, a microenvironment-based particle swarm optimization (MPSO) algorithm is given to optimize the univariate regression features for the current transition sequences. The experimental results show that using the current transition sequence features proposed in this paper for electrical device state recognition can achieve an average accuracy of 97.93%. Compared with the PSO algorithm and CAPSO algorithm, the MPSO algorithm used in this paper achieves the same accuracy with fewer particles and significantly reduces usage time.

This work investigated transfer and change of paint evidences in a case of hit-and-run. Two kinds of attachments were found on the clothes of the victim and they were initially considered paint fragments from the vehicle causing the accident. Infrared spectroscopy (IR), scanning electron microscope–energy dispersive spectrometer, and Microspectrophotometry were applied for examination of paints and clothing fibers. Polyester was detected in one of the attachments and in the clothing fibers of the victim by IR. A traffic accident simulation experiment was designed and conducted to research whether the polyester attachments come from suspected vehicle paints or victim's clothing fibers. The results showed that a melt mixture of transferred paints and clothing fiber was formed after a violent collision. Because the amount of transferred paints was too low to be detectable in the mixture, the components detected by IR were mainly from clothing fibers. Thereby, we inferred that only one kind of attachment and paint fragments existed on the clothes of the victim, and the polyester attachments cannot be used to indicate the composition of suspected vehicle paint. Clothing fibers and paints are both common trace evidence in traffic accident cases, and more attention should be paid to the examination of transferred paints on clothing fibers.

The study proposes for the first time an ultrasonic urea complexation method as a pretreatment for measuring diesel carbon stable isotopes. The carbon isotope ratios of diesel n-alkanes are considered usable for sample tracing. Still, accurate measurement of component isotope ratios requires the elimination of co-elution peaks in the baseline. Traditional urea complexation techniques take over one hour, making sample pretreatment lengthy and the process cumbersome. Aiming to establish a rapid purification method for diesel n-alkanes, the study examines for the first time the effects of urea dosage, ultrasonication time, ultrasonication temperature, types of activators, and their dosages on the recovery rate of n-alkanes in diesel, thus establishing a novel ultrasonic-assisted urea-n-alkane complexation method. Compared to the traditional urea complexation technique, this method reduces the pretreatment time for diesel to less than 0.5 hours, effectively enhancing the pretreatment efficiency of diesel and solving the issue of baseline peaks in the process. The study finds that there is no significant fractionation of carbon isotopes in n-alkane mixed standard solutions before and after treatment, indicating that this method can be applied to the actual detection of diesel n-alkane carbon isotopes, thereby aiding in the rapid determination of diesel sources in forensic investigations.

Color is an important characteristic of textile, and its analysis is of great significance for the forensic characterization of textile. The colorimetry method based on visual observation provides a subjective assessment; the instrument-based color analysis method is objective but requires expensive equipment and professional technicians. In this study, a smartphone-based machine vision method for color analysis was established. A smartphone with a camera was used for image acquisition, and the free software ImageJ was used for image processing. The captured RGB image was first converted to a Lab Stack, and then the target area was selected for L*a*b* value analysis. The influence of acquisition equipment, light source, illumination/photography angle and distance, and sample on color analysis was investigated. Fifteen red textile pieces were analyzed using optimized machine vision methods, and the results were compared with those obtained using the microspectrophotometry by both hierarchical cluster analysis and K-means clustering method. The results of the two methods were consistent, thereby confirming the reliability of the machine vision method. The smartphone-based machine vision color analysis method is cheap, simple, accurate, and objective; thus, it has great potential to be widely used in forensic science.

Triacetone triperoxide (TATP) is a high-power explosive which is often used by criminals. The detection of TATP is of great significance for solving the explosion cases. However, the preconcentration and analysis of trace levels of TATP still pose challenges for analytical researchers. In this study, metal-organic frameworks (MOFs), including IRMOF-8, MOF-5, UIO-66, ZIF-8, and MIL-101(Cr), were immobilized on a stainless steel wire using a physical adhesive method as a solid-phase microextraction (SPME) fiber coating. The prepared fibers with a controllable thickness were used for the extraction of TATP followed by gas chromatography-mass spectrometry (GC-MS) analysis. Under the identical experimental conditions, the IRMOF-8-coated fiber exhibited higher extraction efficiency for TATP than the other fibers. The IRMOF-8-coated fiber was then characterized using scanning electron microscopy and thermogravimetric analysis. The results indicated that the IRMOF-8-coated fiber not only had good thermal and chemical stabilities but also afforded a high TATP extraction efficiency. Under the same extraction conditions, the extraction efficiency of the IRMOF-8-coated fiber was 2-8 times higher than those of commercial fibers. The limit of detection was 13 ng/mL, and linearity was observed in the range of 50-5000 ng/mL with a correlation coefficient greater than 0.998. The intraday repeatability (n = 6), interday repeatability (n = 3), and fiber-to-fiber reproducibility (n = 3), were 4.1 %, 4.8 %, and 8.0 %, respectively. The recoveries of TATP from the simulated tap water and soil samples were 87.32-90.57 % and 88.76-100.93 %, respectively, with relative standard deviations lower than 11.11 % (n = 3). The above method was successfully applied for the detection of TATP transferred from a finger to a paper surface, demonstrating its good application prospects in the analysis of trace TATP.

Gunshot residues (GSR), cartridge projectiles, and casings are frequently encountered evidence in gun-related forensic investigations. However, in circumstances where the investigation of striation marks is impossible, such as unrecovered or deformed projectiles and cartridge casings, GSR deposited on the hands or clothes of the shooter and victim-related items can provide information to establish a link between the suspect, the firearms used, and the victim. Since the formula of primers used by all cartridge manufacturers in China is identical, links based on the conventional morphological and compositional analysis of GSR are difficult to establish. However, the abundance of lead isotopes in primer components of lead styphnate varies significantly, and a fundamental understanding of these differences may facilitate the validation of primer (p)GSR evidence in forensic investigations. Here, 44 pGSR samples were characterized by Pb isotope ratios of 206 Pb/204 Pb, 207 Pb/204 Pb, and 208 Pb/204 Pb using laser ablation multicollector inductively coupled plasma mass spectrometry. There was no obvious mass fractionation of the lead isotope ratios of the primers from individual cartridges analyzed before and after the shooting process, thereby establishing a basis for the comparison of pGSR and unfired cartridges. Evaluation of the results using univariate likelihood ratio (LR) computations revealed low rates of misleading evidence (<0.53%) The results demonstrated that lead isotope ratio analysis of pGSR and LR predictions can provide a practicable method for forensic cartridge discrimination and individualization.

Bullet projectiles are often found in shooting crime scenes and can help identify the cartridges used in shooting events. The most conclusive way to link a fired projectile to a firearm is by identifying the unique markings of the barrel on the projectile or case. But in circumstances where the investigation of striation marks is impossible, lead isotope ratio signature analysis of projectile fragments can facilitate building the linkage of the suspect, the cartridge used and the victim. This work presents a shooting incident happened in a hunting field, where a hunting guide was shot to death. A tiny lead projectile fragment was collected from the victim's head. Pb isotope ratios measured by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) were used to make comparisons between the fragment and the shots seized from two suspects. Additionally, a reference dataset comprising 50 lead bullet projectiles from various manufacturers was characterized using LA-MC-ICPMS. The evaluation of the comparison was carried out by multivariate likelihood ratio (LR) computations based on the reference dataset. The lead isotope ratio and likelihood ratio evaluation methods helped infer the source of the fragment and were highly supportive in the shooting incident investigation.

Gunshot residue (GSR) deposited on the hands or clothes of the shooter and the victim-related items is the most common evidence in gun related cases. It plays an important role in linking the suspects, the guns and the victims in cases. Metallic GSR particles mainly come from the primers of cartridges. The formula of primers is identical for cartridges from different manufacturers in China, which makes them difficult to be discriminated by GSR with the commonplace method of scanning electron microscope scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDS). Lead styphnate is one important component of primers. Measurement of lead isotope ratios of GSR seems reasonable to further discriminate cartridges since the abundance of lead isotopes varies significantly in nature. To make full use of the GSR evidences in cases and make it valid for forensic purposes, it is very important to have a fundamental understanding of the differences of lead isotope ratio between cartridges from different manufacturers and batches. So in this paper, 44 GSR samples were subjected to laser ablation multicollector inductively coupled plasma mass spectrometry analysis and were described by Pb isotope ratios of 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, 208 Pb/ 204 Pb. Univariate likelihood ratio computations were performed by kernel density estimation method for data distribution estimating. It was found that with these three Pb isotope ratios, 0.53 percent of false positive and zero false negative rate were obtained. The results demonstrated that lead isotope ratio analysis and LR evaluation method can provide a practicable method to do cartridge discrimination and individualization. In addition, the change test of Pb isotope ratio proved that there was no obvious mass fractionation in the process of shooting.

One of the key tasks of soil analysis in forensic sciences is to provide information about its diversities and geolocation. In fact, soil analysis is relevant for forensic geologists. In this study, a total of 80 soil samples were collected from eight Chinese cities (10 samples per city). Different minerals and their relative percentages were analyzed by the X-ray diffraction (XRD) method. In addition, the relative amounts of montmorillonite, kaolinite, amphibole, feldspar, calcite, and dolomite provided information about the origin of a soil, either if it came from a northern or southern city of China. The oxide weight percentages of 10 elements of Al2O3, SiO2, Fe2O3, K2O, Na2O, MgO, CaO, P2O5, MnO, and TiO2 were also obtained by using X-ray fluorescence (XRF) from the 80 soil samples. Moreover, principal component analysis (PCA) and hierarchical clustering analysis (HCA) methods were performed for dimensionality reduction, elemental marker identification and soils classification to the city they came from purposes. The eighty soils analyzed in this study could be tracked correctly to their city of origin. The K-Nearest Neighbors (KNN) model was done to evaluate the prediction ability based on the soil elemental composition, and it was confirmed by cross validation methods. The results demonstrated that mineralogical and elemental composition can provide powerful information for soil discrimination and source tracing.

Soil examination can provide useful forensic information about the spatial location and human activities of a suspect. Soil is widely used in criminal investigations. In a case that occurred in the countryside of Jilin Province, in the NE of China, soil was found adhering to clothing on a body. Examination of plant debris in the soil using plant DNA barcoding technique found it to be ginseng root, which indicated that the soil might have come from a ginseng plantation. In the first instance, it helped in finding the place where the body was initially buried. Then a comparison was made between the soil recovered from the body and from the ginseng plantation. Composite analysis of minerals, pollen types and elements provided additional information to assist in making comparisons. Trace amounts of soil located on the body played an important role in locating the burial site and was regarded as the most valuable evidence in convicting the suspect of murder even without the suspect's DNA being available.

Comparison analysis of vehicle headlamp lens fragments can help establish links between the relevant vehicle with crime scenes or provide useful information to search the related vehicles. Headlamp lenses are mainly made of polycarbonate with very few signature additives, which makes them difficult to be discriminated by commonplace examination methods of infrared spectroscopy and scanning electron microscope coupled with energy dispersive X-ray spectroscopy. In this study, molecular weights (Mw) and the polydispersity index (PDI) value of 50 vehicle headlamp lens fragments from different vehicles were measured by gel permeation chromatography, and Hotelling's T2 statistical method was applied to facilitate interpretation of the data. Among the total C 50 2 = 1225 pairs of comparisons between 50 samples, 62 pairs cannot be distinguished, resulting in a discrimination rate of 94.94%. It suggested that the method of gel permeation chromatography and Hotelling's T2 statistical analysis were powerful to make further discrimination between plastic vehicle headlamp lens fragments.

Triacetone triperoxide (TATP) and its byproduct diacetone diperoxide (DADP) are commonly used home-made high explosives in bombing cases and terrorist attacks. However, these two peroxide explosives are unstable and prone to thermal decomposition, leading to challenges in sample collection and preparation in bombing cases. Therefore, there is an urgent need to develop an in situ identification method for TATP and DADP. Compared to the solvent-based swabbing methods commonly used for trace explosive collection, the tape lifting method can collect explosive particles and other potential evidence without damaging fingerprints or DNA. This study aims to develop a tape lifting method to collect trace explosive particles in bombing cases and an in situ method to identify TATP and DADP particles on the sticky side of transparent tape directly using laser confocal Raman spectroscopy. One type of fingerprint tape and two types of office tape were used to collect peroxide explosive particles followed by particle fixation on glass slides. Laser confocal Raman spectroscopy was applied to directly identify target particles, without peeling the attached tape off the glass slide. A solid-state laser emitting at 473 nm was suitable for Raman and imaging analysis of TATP and DADP. To mimic the real situation, the synthetic TATP and DADP were passed through a 100-mesh sieve, respectively. Fifty μg of each explosive powder was weighed, mixed and spread on a wooden table with dust in an area of 10 × 10 cm2. Subsequently, the samples were collected with the fingerprint tape. A targeted area of the tape with suspicious particles was imaged for analysis. Based on the difference between the characteristic Raman bands of TATP and DADP, the band ranges of 530-550 cm-1 and 750-770 cm-1 were selected, respectively, for obtaining the distribution information. The combination of Raman technology and the tape lifting method shows great potential for in situ identification of forensic samples by providing chemical and spatial information.

Soil examination can provide useful forensic information about the spatial location and suspect's activities. Many techniques have been applied for soil comparison and provenance determination in criminal investigations. Pollen and diatom identification, which has the potential to provide an independent ecological assessment of soil evidence, is currently underused in forensic soil analysis. This work presents a case study of application of these methods to help criminal investigation in a murder case, which happened in an irrigation ditch in Hunan Province, southern China. Soils from the suspect's clothes, the exact crime scene spot in the irrigation ditch, along the ditch and the reference ditches were collected and analyzed. In addition to the element and mineral analysis, pollen and diatom assemblages were analyzed for further comparison. The statistical methods of hierarchical cluster and cosine similarity analysis were carried out to assist in soil comparison and provenance determination. The results showed that soil on the suspect's clothes had a high probability to share the same source with the soil from the crime scene in the irrigation ditch. The suspect confessed to murder based largely on the soil examination result even without other evidences.