Preliminary analysis on the characteristics of stamps by 3D printing and their stamped impression.

The development of 3D printing technology has brought new risks and challenges to stamp impression identification. To prevent potential risks, a total of 45 stamps were printed using three types of 3D printers: fused deposition molding (FDM) printer, stereo lithography (SLA) printer, and liquid crystal display (LCD)-based SLA 3D printer, including 6 stamps replicated using LCD-based SLA 3D printer. A preliminary study was conducted on the printed stamps and stamped impressions, and the results showed that stamp are influenced by various factors such as printer type, printing material, the technology level of the producer, mold parameters such as font, size, printing parameters, slicing direction, and polishing process, etc., resulting in significant differences in characteristics. However, there are some obviously common characteristics such as missing of strokes, exposure of white and mottled phenomenon in the impression stamped by the 3D produced stamp. The impression of stamp replicated with an LCD 3D printer can be easily identified since it is difficult to achieve consistency with the real impression in detail characteristics.

MIPs: multi-locus intron polymorphisms in species identification and population genomics.

The study of species groups in which the presence of interspecific hybridization or introgression phenomena is known or suspected involves analysing shared bi-parentally inherited molecular markers. Current methods are based on different categories of markers among which the classical microsatellites or the more recent genome wide approaches for the analyses of thousands of SNPs or hundreds of microhaplotypes through high throughput sequencing. Our approach utilizes intron-targeted amplicon sequencing to characterise multi-locus intron polymorphisms (MIPs) and assess genetic diversity. These highly variable intron regions, combined with inter-specific transferable loci, serve as powerful multiple-SNP markers potentially suitable for various applications, from species and hybrid identification to population comparisons, without prior species knowledge. We developed the first panel of MIPs highly transferable across fish genomes, effectively distinguishing between species, even those closely related, and populations with different structures. MIPs offer versatile, hypervariable nuclear markers and promise to be especially useful when multiple nuclear loci must be genotyped across different species, such as for the monitoring of interspecific hybridization. Moreover, the relatively long sequences obtained ease the development of single-locus PCR-based diagnostic markers. This method, here demonstrated in teleost fishes, can be readily applied to other taxa, unlocking a new source of genetic variation.

Evaluation of Sexual Dimorphism Using Condylar and Coronoid Mandibular Parameters in Orthopantomograms: A Pilot Study.

Background Gender determination is critical to forensic science and medico-legal applications. Given that it is the most dimorphic bone in the skull and is frequently found intact, the mandibular bone may be extremely important in determining gender. Orthopantomograms (OPGs) are quite helpful in accurately estimating age and sex in this regard. It is a laborious task for forensics to determine the gender of victims of mass casualties, natural disasters, and severely dismembered bodies. The mandible, which is susceptible to development spurts, has a high degree of accuracy for determining sex. Aim  This study aims to evaluate the potential use of coronoid height and condylar height as reliable anatomical markers for determining gender. Materials and methods In this study, 100 samples were used as study samples, 50 of which were male and 50 of which were female, in the age group of 20-30 years. The OPGs were obtained using a Planmeca Promax Scara 3 Digital OPG Machine (Planmeca, Helsinki, Finland), with settings of 70 kVp, 8 mA for 0.9 seconds, ensuring a 1:1 ratio. The images were then transferred to Planmeca Romexis® Viewer Software, Version 6.0 (Planmeca Oy, Helsinki, Finland) for measurement recording. Results Descriptive statistical analysis was done for this study and discriminant analysis was also done to create a population-specific formula. Results showed that the standard mean error for males concerning condylar height was 2.3 and coronoid height was 0.7. The standard mean error for females by condylar height was 1.6 and coronoid height was 0.6. The p-value was significant for coronoid height in both males and females. The p-value was not clinically significant for condylar height in both males and females. Conclusion The study's findings indicate that a larger mandibular angle is advantageous for gender assessment and helps with gender dimorphism. Out of both the parameters evaluated, coronoid height has shown statistical significance in both males and females. Hence, the study concludes that the parameter, coronoid height can be utilized to assess the gender of an individual.

Reliability of predictive models based on the mesiodistal and buccolingual diameters of permanent canine teeth for sex estimation in forensic contexts: A systematic review and meta-analysis.

This study aimed to assess the reliability of predictive models for sex estimation based on permanent canine size. A systematic literature review was performed by following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). Six electronic databases were searched as the primary source of information. As a secondary source of information, a manual search was performed to identify additional relevant studies not captured in the initial search. After assessing the methodological quality and risk of bias with the Joanna Briggs Institute Critical Appraisal Tools for Systematic Reviews, the data were subjected to statistical tests for a meta-analysis of diagnostic test accuracy and Higgin's I2 statistic to evaluate the heterogeneity between the eligible studies. The systematic search resulted in 21 studies for qualitative synthesis, and 13 of them were selected for quantitative analysis. The analysis of 25 univariate predictive models showed an estimated sensitivity of 77.2 % and specificity of 67.1 %. Meta-regression analyses were performed for dental arch, the type of diameter and dental region outcomes for these univariate predictive models. Dental arch (p = 0.029) and the dental region of measurement (p = 0.001) were significant modifiers. The analysis of 25 multivariate predictive models showed an estimated sensitivity of 82.6 % and specificity of 70.1 %. There were significant methodological limitations and substantial heterogeneity among the included studies. Based on the results, there is insufficient high-quality scientific evidence to support the safe use of predictive models based on permanent canine measurements as the exclusive method for sex estimation in forensic settings.

Evaluation of Bitemark Analysis's Potential Application in Forensic Identification: A Systematic Review.

Bitemark analysis involves the examination of both patterned injuries and contextual circumstances, combining morphological and positional data. Considering the uniqueness of human dentition, bitemarks caused by teeth on skin or impressions on flexible surfaces could assist in human identification. AIMS: to investigate the available literature systematically and evaluate the scientific evidence published over the past decade concerning the potential application of bitemark analysis in forensic identification. METHODS: Two researchers meticulously searched electronic databases from January 2012 to December 2023, including Scopus, PubMed, Web of Science, and the Cochrane Library. Adhering to the PRISMA statement guidelines, this review employed appropriate medical subject headings (MeSHs) and free-text synonyms. Strict inclusion and exclusion criteria were applied during article retrieval. RESULTS: The findings yielded controversial outcomes. Approximately two-thirds of the articles concluded that bitemark analysis is useful in forensic identification, while the remaining articles did not report statistically significant outcomes and cautioned against relying solely on bitemark analysis for identification. CONCLUSIONS: The authors assert that bitemark analysis can be a reliable and complementary method for forensic identification, contingent upon the establishment and adoption of a universally accepted global protocol for data collection, processing, and interpretation. Undoubtedly, recent years have witnessed a notable increase in research focused on bitemark identification, driven by the goal of achieving quantitative, objective, reproducible, and accurate results.

Dental Anomalies: An Identification Marker in Forensics.

Aim This study aims to evaluate the non-morphological traits of the South Indian population. Introduction Dental morphological traits, also known as non-metric dental traits, exhibit variation in appearance both within and between groups. The study analyzed the non-metric traits among the South Indian population, as few variants can be grouped within the population.  Materials and methods A total of 500 extracted tooth samples were collected. The dental non-metric traits that were evaluated are the cusp of Carabelli (CC), Talon's cusp (TC), shoveled incisor (SI), peg-shaped lateral incisor (PL), protostylid (PR), Dryopithecus pattern groove (DP), hypoconulid (HY), parastyle (PA), multiple parastyle (MPA), paracone (PC), Bushman's canine (BC), interruption groove (IG), tuberculum dentale (TD), tuberculum intermedium (TI), radix entomolaris (RE), fusion (F), radiculous premolar (RP), dilaceration (D), dens evaginatus (DE), and enamel pearl (EP).  Results Out of 20 dental non-metric traits that were evaluated in the study, 14 traits were identified to be common within the population. The prevalence were as follows: cusp of Carabelli (52%), shoveled incisor (8.2%), peg-shaped lateral incisor (7.4%), parastyle (0.8%), multiple parastyle (0.2%), Bushman's canine (0.4%), interruption groove (2.2%), tuberculum intermedium (0.6%), radix entomolaris (39.6%), fusion (2.8%), radiculous premolar (0.2%), dilaceration (58.2%), dens evaginatus (1.2%), and enamel pearl (0.8%) among the South Indian population.  Conclusion The current study was discovered to have more Carabelli traits, shoveled incisors, radix entomolaris, and dilaceration than other non-metric features. This shows that these characteristics are more prevalent in the South Indian population, which could be one of the strategies used to validate human identification in a forensic context.

Study of Lip Conditions Associated with Lip Print Patterns: A New Perspective on Cheiloscopy

SUMMARY: Although almost all studies exclude lip conditions because they would affect furrow patterns, some authors maintain that they should be considered temporary or permanent disabilities, all of which require further research in this context.We present a study in which we associate lip conditions with lip print patterns to associate both morphological elements for fieldwork purposes. Fifty-seven women and 48 men aged between 19 and 38 years who resided in Temuco (Chile) were included. The lip conditions and their prints were recorded, and an analysis, comparison, evaluation, and verification protocol (ACE-V) for lip prints was applied. Of the participants, 27.4 % had healthy lips, while 71.7 % had some type of condition. Although patterns related to temporary and permanent lip conditions were recognized in the lip prints in a non-significant way, the diagnosis of "healthy" or "altered" lip status could be made significantly by a calibrated examiner. Although these conditions do not represent identifying variables without empirical studies to validate them, they can affect the quality of the evaluated lip print; therefore, they should be recognized during the analyses considering the prevalence of these conditions.

Aunque casi todos los estudios excluyen las afecciones labiales pues afectarían los patrones de sus surcos y huellas, algunos autores sostienen que deben ser consideradas alteraciones temporales o permanentes, por lo que se requiere mayor investigación en este aspecto. Se presenta un estudio en el que se asocian afecciones labiales con sus patrones de huellas para evaluar conjuntamente ambos elementos morfológicos con fines de trabajo forense de campo. Se incluyeron 57 mujeres y 48 hombres con edades entre 19 y 38 años residentes en Temuco (Chile). Se registraron las afecciones de los labios y sus huellas, y se aplicó un protocolo de análisis, comparación, evaluación y verificación (ACE-V) para las huellas labiales. De los participantes, el 27,4 % tenía labios sanos, mientras que el 71,7 % presentaba algún tipo de afección. Aunque los patrones relacionados con afecciones labiales temporales y permanentes se reconocieron en las huellas labiales de manera no significativa, un examinador calibrado podría realizar significativamente el diagnóstico de estado labial "sano" o "alterado". Si bien estas condiciones no representan variables de identificación sin estudios empíricos que las validen, pueden afectar la calidad de la impresión labial evaluada; por lo tanto, deben ser reconocidos durante los análisis considerando la prevalencia de estas condiciones.

Exploring the role of the human microbiome in forensic identification: opportunities and challenges.

Forensic microbiology is rapidly emerging as a novel tool for human identification. The human microbiome, comprising diverse microbial communities including fungi, bacteria, protozoa, and viruses, is unique to each individual, offering a new dimension to forensic investigations. While traditional identification methods primarily rely on DNA profiling and fingerprint analysis, they face limitations when complete DNA or fingerprints profiles are unattainable or degraded. In this context, the microbial signatures of the human skin microbiome present a promising alternative due to their resilience to environmental stresses and individual-specific composition. This review explores the potential of microbiome analysis in forensic human identification, evaluating its applications, advantages, limitations, and future prospects. The uniqueness of an individual's microbial community, particularly the skin microbiota, can provide distinctive biological markers for identification purposes, while technological advancements like 16 S rRNA sequencing and metagenomic shotgun sequencing are enhancing the specificity of microbial identification, enabling detailed analysis of these complex ecological communities. Despite these promising findings, current research has not yet achieved a level of identification probability that could establish microbial analysis as a stand-alone evidence tool. Therefore, it is presently considered ancillary to traditional methods, contributing to a more comprehensive biological profile of individuals.

Assessment of Palatal Rugae to Aid in Gender Identification in Hazaribag Population-A Cross-Sectional Study.

Background: This research paper aims to investigate the effectiveness of gender identification utilizing palatal rugae. Materials and Methods: The size of the sample that was selected included 100 people. They were made up of 50 men and 50 women, all in between the ages of 18 and 25. To examine their palatal rugae patterns, casts were made after taking maxillary impressions. Based on the size and rugae amount found on the left as well as the right sides, the palatal rugae patterns were investigated. Rugae patterns have been recognized based on the categorization provided by Thomas and Kotze (1983). Statistical Analysis: Chi-square analysis has been used. Results: There were comparative variations in the shape of rugae patterns among male and female individuals. The study revealed that the circular pattern was higher in males (P < 0.01) as compared to females and the unification pattern was comparatively greater in females (P < 0.05) as compared to males. The most predominant pattern that was seen in both genders was the wavy pattern that was seen to be present in 57.17% of males and 53.42% of females. The rugae number on the right and left sides did not exhibit any significant variations. Conclusions: This research thus exhibits a relevant difference in patterns of rugae and also confirms the uniqueness of patterns in each individual. Hence, it could be utilized as an adjunct to other tools for identification in the forensic sciences.

Three decades after the publication of the Lamendin method for adult age-at-death estimation: Methodological evolution of the procedure and interpretations.

More than three decades have passed since the publication of Lamendin et al.'s proposal in 1992. Over this time, numerous investigations have been conducted to assess the applicability of the technique in different populations with acceptable results in terms of estimation errors. The proposal by Lamendin and colleagues remains relevant today, and has made a significant contribution to adult age-at-death estimation due to its simplicity, repeatability, replicability, and high performance. Indeed, significant progress towards systematizing and strengthening the procedure has been reported in the published literature. One noteworthy advancement is the development of an international database that supports the use of Bayesian statistics for age-at-death estimation. This resource plays a crucial role in standardizing the methodology and improving the reliability for obtaining more reliable results on a global scale. The aim of this study is to investigate the historical evolution of the technique, to assess the accuracy of the results obtained by different analytic procedures, and to explore its impact in forensic applications through a systematic analysis of the specialized literature on this field. The current state of research indicates that this type of methodological research is an ongoing process, far from being completed. Many questions and challenges that require further attention to address effectively these issues remain unanswered, such as the development of non-linear regressions and probabilistic approaches, the deepening of procedures that improve global approximations, and the intensification of research focused on achieving more accurate estimations among individuals over 70 years-old. However, studies generally agree that the Lamendin technique works well for individuals between the ages of 30-60 years. It is still in force today, although the method has been significantly perfected. Despite the degree of research development in this area, further efforts are needed to improve the understanding and performance of these kinds of procedures. This will ultimately lead to an improvement in the accuracy and reliability of forensic investigation results worldwide.

Starch treatment improves the salivary proteome for subject identification purposes.

Identification of subjects, including perpetrators, is one of the most crucial goals of forensic science. Saliva is among the most common biological fluids found at crime scenes, containing identifiable components. DNA has been the most prominent identifier to date, but its analysis can be complex due to low DNA yields and issues preserving its integrity at the crime scene. Proteins are emerging as viable candidates for subject identification. Previous work has shown that the salivary proteome of the least-abundant proteins may be helpful for subject identification, but more optimized techniques are needed. Among them is removing the most abundant proteins, such as salivary α-amylase. Starch treatment of saliva samples elicited the removal of this enzyme and that of glycosylated, low-molecular-weight proteins, proteases, and immunoglobulins, resulting in a saliva proteome profile enriched with a subset of proteins, allowing a more reliable and nuanced subject identification.

Transcending time: the forensic anthropological case study of three unidentified transgender women in Italy in the early 1990s.

In forensic anthropology, the estimation of skeletal sex results in a dichotomous outcome: male or female. This poses challenges when dealing with transgender individuals. Italy has the highest rate per capita of transgender murders, making their identification a compelling issue. This study presents three cases of unidentified skeletal remains of transgender women (MtF) that underwent autopsies in the 1990s at the Institute of Legal Medicine of Milan. The transgender status of the individuals was determined from the autopsy records which indicated the co-existence of breast implants and male genitalia. The biological profile was created by estimating sex, age, ancestry, and stature, and the bones were investigated looking for evidence of Facial Feminization Surgery (FFS). Anthropological estimations revealed that the skeletons belong to male, adults, European individuals, between 164 and 184 cm. Fragmented gelatinous masses were found in association with two skeletons, which were interpreted as remnants of breast implants. In two cases, signs of remodeling of the cortical surface were observed on the zygomatic bones, although the bone marks observed here were not specific enough to link them to FFS. Despite some limitations, this study highlights the need for greater awareness among practitioners about this limitedly addressed issue, advocating for a more inclusive forensic anthropology that strives to improve methods and interpretation of evidence for the identification of transgender individuals.

Assessing the morphology and bone mineral density of the immature pars lateralis as an indicator of age.

Age estimation is crucial when the state of personhood is a mitigating factor in the identification of immature human remains. The maturation sequence of immature bones is a valuable alternative to dental development and eruption standards. Bordering the foramen magnum and pars basilaris, the pars lateralis is somewhat understudied. The aim of this study was to comprehensively describe the morphology of the immature human pars lateralis bone. Human pars laterali were sourced from the crania of 103 immature individuals of unknown provenance from the Johannesburg Forensic Paediatric Collection (JFPC), University of the Witwatersrand (HREC-Medical: M210855). The study sample was subdivided into early prenatal (younger than 30 gestational weeks; n = 32), prenatal (30-40 gestational weeks, n = 41) and postnatal (birth to 7.5 months, n = 30) age groups. The morphology of the pars laterali was studied using a combination of bone mineral density pattern assessments, geometric morphometrics and stereomicroscopy. Bone mineral density in postnatal individuals was lower when compared with the prenatal individuals. No statistically significant differences between density points were noted. The overall shape of the pars lateralis changed from a triangular shape in the early prenatal individuals to a fan-like quadrilateral bone in postnatal individuals. The angulation of the medial border for the foramen magnum highlighted a change in shape between straight in the early prenatal cohort to V-shaped in the postnatal individuals. The various technical approaches used in the current study provided detailed descriptions of the pars lateralis which establishes a valuable foundation for diagnostic criteria employing morphological predictors for biological profiling.

Two-Dimensional Geometric Morphometric Method on Frontal Sinus for Race Estimation: A Lateral Skull Radiograph Study

@#Introduction: Race estimation of unknown individual is essential in forensic investigation. The resiliency of frontal sinus makes it a potential tool for biological profiling, particularly in cases where fragmented skeleton persists. Geometric morphometrics is an efficient way to characterise shape. However, the use of frontal sinus to identify race of Malaysians is yet to be investigated. This research employed a two-dimensional (2D) geometric morphometric to examine the morphological differences of the frontal sinus among the major races in Malaysia. Methods: Lateral skull radiographs which comprising of 453 adult Malaysian (151 Malays, Chinese and Indian respectively) were used. The 2D landmarks of eight were placed on the digitalized radiographs and 2D geometric morphometric analysis was performed using MorphoJ software. Results: Procrustes ANOVA revealed a significantly different frontal sinus shape (p-value < 0.05) between races. Canonical variate analysis showed significantly different frontal sinus morphology (p-value < 0.05) between Malay and Indian as well as Chinese and Indian. Discriminant function analysis with cross-validation demonstrated a 57.4% accuracy rate. Conclusion: This population-specific study based on frontal sinus of Malaysians using the 2D geometric morphometric, though less reliable, sheds new light on the potential applicability of this method for race estimation purpose.

The effect of tea catechins on the forensic identification of urine: Urine camouflage to evade drug tests.

BACKGROUND: We encountered a urine sample suspected of being mixed with tea, submitted by a suspect attempting to camouflage illegal drugs. Although urine should turn reddish-pink during a urea test with p-Dimethylaminocinnamaldehyde (DAC), this suspect's sample exhibited a blue coloration when tested with DAC. AIM: Our aim was to examine the influence and mechanism of green tea on various urine identification tests. RESULTS: Our examination revealed that DAC forms a compound with the urea in urine, resulting in a reddish pink coloration with a molecular weight of 217. However, it has been reported that DAC binds to polyphenols such as catechin. In the case of catechin, DAC binds to the C8 position, forming a compound that exhibits the highest absorption at 640 nm and appears blue. we investigated the effect of urine from volunteers who had consumed a large amount of catechin on the urea test with DAC. Additionally, we carried out quantitative analysis of catechin in urine by LC-MS/MS after enzymatic treatment with ß-glucuronidase. The concentration of urinary excreted catechin reached its peak approximately 3 to 4 h after ingestion. During the DAC test, urine samples collected 3 to 4 h after catechin ingestion displayed a bluish pink color, but not the blue color observed in the original suspect sample. CONCLUSION: This study investigated the impact of catechin on urine tests, revealing that a blue color in the DAC test indicates a high likelihood of camouflage by the suspect.

Development, detection and decipherment of obfuscated fingerprints in humans: Implications for forensic casework.

Fingerprints have been widely used and accepted as an effective method of human identification. This biometric tool aids in criminal investigations for personal identity for over a century. Whilst the Automatic Fingerprint Identification System (AFIS) has bolstered security efforts, it has also opened doors to potential scams, affecting both civilian and law enforcement operations. Despite extensive research on fingerprint authentication issues, very little attention has been given to addressing the problem of fingerprint alteration or obfuscation. Fraudsters, with the guidance of experts, have developed new techniques to obscure their fingerprints intentionally. Fingerprint obfuscation is the deliberate alteration of fingerprint patterns with the aim of concealing their true identity, raising concerns amongst security and investigative organizations. The objective of the current communication is to highlight the numerous techniques used for obfuscation, forgery and alteration of fingerprints in humans. It further accentuates the need for identification and interpretation of these altered fingerprints and recommends notifying law enforcement agencies of potential threats.

Gender Determination Based on CBCT Maxillary Sinus Analysis: A Systematic Review.

Gender determination is an essential element for human identification in forensic medicine, to which the maxillary sinuses may contribute as they remain intact even after severe damage to the skull and other structures. AIM: To evaluate scientific evidence published over the last decade to determine whether maxillary sinus dimensions and volume may constitute useful parameters for forensic identification and gender determination, based only on cone-beam computed tomography images (CBCT). METHODS: This review adhered to the PRISMA statement's criteria. Four databases were searched for articles published between January 2010 and April 2023. RESULTS: Initially, 1719 records were identified. After screening, there were 2475 participants in the included studies. Of the fifteen articles selected, five reported data assessing only volumetric measurements of the maxillary sinus, seven reported data calculating only linear measurements and three reported data by combining findings of both linear and volumetric measurements of the maxillary sinus. Maxillary sinus volume was significantly higher in male participants. Maxillary sinus height was the best discriminating parameter for forensic identification with an overall accuracy ranging from 70% to 80%. CONCLUSIONS: Maxillary sinus measurements revealed anatomic variability between genders, and this approach can be applied as a complementary method for human identification.

Machine Learning Models for Prediction of Sex Based on Lumbar Vertebral Morphometry.

BACKGROUND: Identifying skeletal remains has been and will remain a challenge for forensic experts and forensic anthropologists, especially in disasters with multiple victims or skeletal remains in an advanced stage of decomposition. This study examined the performance of two machine learning (ML) algorithms in predicting the person's sex based only on the morphometry of L1-L5 lumbar vertebrae collected recently from Romanian individuals. The purpose of the present study was to assess whether by using the machine learning (ML) techniques one can obtain a reliable prediction of sex in forensic identification based only on the parameters obtained from the metric analysis of the lumbar spine. METHOD: This paper built and tuned predictive models with two of the most popular techniques for classification, RF (random forest) and XGB (xgboost). Both series of models used cross-validation and a grid search to find the best combination of hyper-parameters. The best models were selected based on the ROC_AUC (area under curve) metric. RESULTS: The L1-L5 lumbar vertebrae exhibit sexual dimorphism and can be used as predictors in sex prediction. Out of the eight significant predictors for sex, six were found to be particularly important for the RF model, while only three were determined to be important by the XGB model. CONCLUSIONS: Even if the data set was small (149 observations), both RF and XGB techniques reliably predicted a person's sex based only on the L1-L5 measurements. This can prove valuable, especially when only skeletal remains are available. With minor adjustments, the presented ML setup can be transformed into an interactive web service, freely accessible to forensic anthropologists, in which, after entering the L1-L5 measurements of a body/cadaver, they can predict the person's sex.

The uselessness of using salivary microbiota in forensic identification purposes of a person with recent antibiotic use.

The detection of microbial flora changes in saliva samples because of antibiotic use through advanced molecular genetic analysis is important for forensic and clinical applications. This study aims to reveal the variability in the microbial structure of human saliva after antibiotic use with metagenomic analysis techniques from a forensic point of view. Within the scope of the study, saliva samples were collected from patients who were under the effect of regional anesthesia to be administered a standardized course of antibiotic therapy that lasted for a week. The analysis was conducted on 56 saliva samples from 14 individuals over four different time intervals. Isolation of the 16S rRNA region and PCR analysis were performed prior to sequence analysis to determine the microbiome structure of the samples at phylum, genus, and species levels. As expected, changes were observed in bacterial species found in saliva samples after administration of antibiotics and this was linked to the specific type of antibiotics that were administered. This change was statistically significant for Firmicutes, Spirochetes, and Verrucomicrobiota. Furthermore, although the oral microbiome tends to return to its former state at the phylum and genus level within a 4-week period after the start of antibiotic use, it is observed that the change, especially in some bacterial species, still continues. The findings of this study show that because of the inability of stabilization at species-level in a period of 4 weeks from the start of antibiotic use, it is not suitable to assess saliva samples at species-level for forensic identification.

Construction and evaluation of in-house methylation-sensitive SNaPshot system and three classification prediction models for identifying the tissue origin of body fluid. / 鉴定体液来源的甲基化敏感性SNaPshot体系及三种预测模型的构建与评估.

The identification of tissue origin of body fluid can provide clues and evidence for criminal case investigations. To establish an efficient method for identifying body fluid in forensic cases, eight novel body fluid-specific DNA methylation markers were selected in this study, and a multiplex singlebase extension reaction (SNaPshot) system for these markers was constructed for the identification of five common body fluids (venous blood, saliva, menstrual blood, vaginal fluid, and semen). The results indicated that the in-house system showed good species specificity, sensitivity, and ability to identify mixed biological samples. At the same time, an artificial body fluid prediction model and two machine learning prediction models based on the support vector machine (SVM) and random forest (RF) algorithms were constructed using previous research data, and these models were validated using the detection data obtained in this study (n=95). The accuracy of the prediction model based on experience was 95.79%; the prediction accuracy of the SVM prediction model was 100.00% for four kinds of body fluids except saliva (96.84%); and the prediction accuracy of the RF prediction model was 100.00% for all five kinds of body fluids. In conclusion, the in-house SNaPshot system and RF prediction model could achieve accurate tissue origin identification of body fluids.