Identification of five types of forensic body fluids based on stepwise discriminant analysis

Differentiation of five forensically relevant body fluids using a small set of microRNA markers

In forensic investigations, identifying the type of body fluid allows for the interpretation of biological evidence at the activity level. Over the past two decades, significant research efforts have focused on developing molecular methods for this purpose. MicroRNAs (miRNAs) hold great promise due to their tissue-specific expression, abundance, lack of splice variants, and relative stability. Although initial findings are promising, achieving consistent results across studies is still challenging, underscoring the necessity for both original and replication studies. To address this, we selected 18 miRNA candidates and tested them on 6 body fluids commonly encountered in forensic cases: peripheral blood, menstrual blood, saliva, semen, vaginal secretion, and skin. Using reverse transcription quantitative PCR analysis, we confirmed eight miRNA candidates (miR-144-3p, miR-451a, miR-205-5p, miR-214-3p, miR-888-5p, miR-891a-5p, miR-193b-3p, miR-1260b) with high tissue specificity and four (miR-203a-3p, miR-141-3p, miR-200b-3p, miR-4286) with lesser discrimination ability but still contributing to body fluid differentiation. Through principal component analysis and hierarchical clustering, the set of 12 miRNAs successfully distinguished all body fluids, including the challenging discrimination of blood from menstrual blood and saliva from vaginal secretion. In conclusion, our results provide additional data supporting the use of a small set of miRNAs for predicting common body fluids in forensic contexts. Large population data need to be gathered to develop a body fluid prediction model and assess its accuracy.

Forensic stability evaluation of selected miRNA and circRNA markers in human bloodstained samples exposed to different environmental conditions

Recently, RNA markers have been used to identify tissue origins of different kinds of body fluids. Herein, circRNA and miRNA markers were carried out to examine the presence or absence of peripheral blood (PB) in bloodstained samples exposed to different external environmental conditions, which mimicked PB samples left at the crime scenes. PB samples were placed on sterile swabs and then exposed to different high temperatures (37°C, 55°C and 95°C) and ultraviolet light irradiation for 0 d, 0.5 d, 1 d, 3 d, and 7 d, ultra-low and low temperatures (-80°C, -20°C, and 4°C) for 30 d, 180 d and 365 d and different kinds of disinfectants. Total RNA was extracted from bloodstained samples under the above different conditions, and the expressions of target RNAs (including miR16-5p, miR451a, circ0000095, and two reference genes RNU6b and 18 S rRNA) were detected by the reverse transcription-quantitative polymerase chain reaction (RT-qPCR) method. Results showed that these selected RNA markers could be successfully measured at all observation points with their unique degradation rates, which exhibited relative stability in degraded bloodstained samples exposed to different environmental conditions. This study provides insights into the applications of these studied miRNA and circRNA markers in forensic science.

Advances in body fluid identification: MiRNA markers as powerful tool

Body fluids are one of the most encountered types of evidence in any crime and are commonly used for identifying a person's identity. In addition to these, they are also useful in ascertaining the nature of crime by determining the ty pe of fluid such as blood, semen, saliva, urine etc. Body fluids collected from crime scenes are mostly found in degraded, trace amounts and/or mixed with other fluids. However, the existing immunological and enzyme-based methods used for differentiating these fluids show limited specificity and sensitivity in such cases. To overcome these challenges, a new method utilizing microRNA expression of the body fluids has been proposed. This method is believed to be non-destructive as well as sensitive in nature and researches have shown promising results for highly degraded samples as well. This systematic review focuses on and explores the use and reliability of miRNAs in body fluid identification. It also summarizes the researches conducted on various aspects of miRNA in terms of body fluid examination in forensic investigations.

Analysis of MiR-20b, MIR-197 markers for differentiation between forensic body fluids encountered in sexual assault cases

Identifying body fluids can be a critical clue that aids in reconstructing the crime scene. Semen and vaginal fluid identification is crucial, especially in cases of sexual assault. The majority of forensic studies focused on identifying normal body fluids and neglected the expression variation of semen in pathology. To differentiate between vaginal fluids, fertile and infertile semen samples (oligospermia and azoospermia) using miR 20b and miR197. A total of 48 body fluid samples, divided as 16 vaginal fluids, 16 fertile semen, and 16 infertile semen samples (8 with oligospermia and 8 with azoospermia), were collected, and the expression levels of miR-20b and miR-197 were detected by the SYBR Green real-time quantitative PCR technique. Our results showed significant different expression of these miRNAs in normal semen compared to vaginal and infertile semen. Moreover, we designed a model based on Fisher's discriminant function to forecast the group affiliations of unidentified samples. With three novel equations, we were able to accurately distinguish between semen and vaginal fluid, fertile and infertile semen, and oligospermia and azoospermia semen samples with validation accuracy of 81.3%, 100%, and 100%, respectively. MiR-20b and miR-197 expression levels are efficient and appropriate markers to distinguish semen from vaginal fluid and to differentiate between fertile and infertile semen samples. However, the present study is a preliminary study based on clinical samples, and the potential role of these markers in differentiating real crime scene samples is still unknown, so we recommend further research to investigate these markers expression while using forensic samples.

Research progress and potential application of microRNA and other non-coding RNAs in forensic medicine

At present, epigenetic markers have been extensively studied in various fields and have a high value in forensic medicine due to their unique mode of inheritance, which does not involve DNA sequence alterations. As an epigenetic phenomenon that plays an important role in gene expression, non-coding RNAs (ncRNAs) act as key factors mediating gene silencing, participating in cell division, and regulating immune response and other important biological processes. With the development of molecular biology, genetics, bioinformatics, and next-generation sequencing (NGS) technology, ncRNAs such as microRNA (miRNA), circular RNA (circRNA), long non-coding RNA (lncRNA), and P-element induced wimpy testis (PIWI)-interacting RNA (piRNA) are increasingly been shown to have potential in the practice of forensic medicine. NcRNAs, mainly miRNA, may provide new strategies and methods for the identification of tissues and body fluids, cause-of-death analysis, time-related estimation, age estimation, and the identification of monozygotic twins. In this review, we describe the research progress and application status of ncRNAs, mainly miRNA, and other ncRNAs such as circRNA, lncRNA, and piRNA, in forensic practice, including the identification of tissues and body fluids, cause-of-death analysis, time-related estimation, age estimation, and the identification of monozygotic twins. The close links between ncRNAs and forensic medicine are presented, and their research values and application prospects in forensic medicine are also discussed.

A combined molecular approach utilizing microbial DNA and microRNAs in a qPCR multiplex for the classification of five forensically relevant body fluids

Body fluid identification is an essential step in the forensic biology workflow that can assist DNA analysts in determining where to collect DNA evidence. Current presumptive tests lack the specificity that molecular techniques can achieve; therefore, molecular methods, including microRNA (miRNA) and microbial signature characterization, have been extensively researched in the forensic community. Limitations of each method suggest combining molecular markers to increase the discrimination efficiency of multiple body fluids from a single assay. While microbial signatures have been successful in identifying fluids with high bacterial abundances, microRNAs have shown promise in fluids with low microbial abundance (blood and semen). This project synergized the benefits of microRNAs and microbial DNA to identify multiple body fluids using DNA extracts. A reverse transcription (RT)-qPCR duplex targeting miR-891a and let-7g was validated, and miR-891a differential expression was significantly different between blood and semen. The miRNA duplex was incorporated into a previously reported qPCR multiplex targeting 16S rRNA genes of Lactobacillus crispatus, Bacteroides uniformis, and Streptococcus salivarius to presumptively identify vaginal/menstrual secretions, feces, and saliva, respectively. The combined classification regression tree model resulted in the presumptive classification of five body fluids with 94.6% overall accuracy, now including blood and semen identification. These results provide proof of concept that microRNAs and microbial DNA can classify multiple body fluids simultaneously at the quantification step of the current forensic DNA workflow.

Forensic validation of a combined analysis of mRNA and miRNA markers for precise tissue origin inferences of five kinds of body fluids by RT-qPCR

Correctly inferring the tissue origin types of forensic-relevant body fluids left at a crime scene is beneficial for reconstructing a crime scene. However, it is still a challenge to accurately identify different kinds of body fluids at a crime scene. Shorter sequence length and anti-degradation microRNA (miRNA) can be used to infer the tissue sources of biological fluid traces, but a limited number of miRNAs are tissue specific. The application of messenger RNA (mRNA) has been confirmed by different studies based on its high tissue specificity. According to the differential expression features of mRNA or miRNA in forensically relevant body fluids, this study developed a simultaneously reversed mRNA and miRNA system and then used these two types of RNAs for the determinations of five common kinds of body fluids. Compared with previously reported single kind of mRNA or miRNA assay, the combined mRNA and miRNA system showed good advantages for human body fluid identifications, especially it could be applied in mixed samples. In conclusion, the obtained results indicated that this combined mRNA and miRNA system might provide a scientific and accurate reference for body fluid identifications.

Development and application of a multiplex PCR system for forensic salivary identification

In forensics, accurate identification of the origin of body fluids is essential for reconstructing a crime scene or presenting strong evidence in court. Microorganisms have demonstrated great potential in body fluid identification. We developed a multiplex PCR system for forensic salivary identification, which contains five types of bacteria:Streptococcus salivarius, Neisseria subflava, Streptococcus. mutans, Bacteroides thetaiotaomicron, and Bacteroides. uniformis. And the validated studies were carried out following the validation guidelines for DNA analysis methods developed by the Scientific Working Group on DNA Analysis Methods (SWGDAM), which included tests for sensitivity, species specificity, repeatability, stability, and mixed samples, trace samples, case samples, and a population study. Our result depicted that the lowest detection limit of the system was 0.01 ng template DNA. Moreover, the corresponding bacteria can still be detected when the amount of saliva input is low to 0.1 μL for DNA extraction. In addition, the target bacteria were not detected in the DNA of human, seven common animals, and seven bacteria DNA and in nine other body fluid samples (skin, semen, blood, menstrual blood, nasal mucus, sweat, tears, urine, and vaginal secretions). Six common inhibitors such as indigo, EDTA, hemoglobin, calcium ions, alcohol and humic acid were well tolerated by the system. What is more, the salivary identification system recognized the saliva component in all mixed samples and simulated case samples. Among 400 unrelated individuals from the Chinese Han population analyzed by this novel system, the detection rates of N. subflava, S. salivarius, and S. mutans were 97.75%, 70.75%, and 19.75%, respectively, with 100% identification of saliva. In conclusion, the salivary identification system has good sensitivity, specificity, stability, and accuracy, which can be a new effective tool for saliva identification.

Screening and evaluation of endogenous reference genes for miRNA expression analysis in forensic body fluid samples

MicroRNA (miRNA)-based methods for body fluid identification are promising tools in the practice of forensic science. The selection of appropriate endogenous reference genes as normalizers for the relative quantification of miRNA expression levels using quantitative reverse transcription-polymerase chain reaction (RTqPCR) is essential to avoid errors and improve the comparability of miRNA expression level data among different body fluids. In this study, small RNAs were isolated from individual donations of five forensically relevant body fluids (peripheral blood, menstrual blood, saliva, semen and vaginal secretions). Thirty-seven samples were subjected to high-throughput miRNA sequencing. By combining our results with those obtained through a literature investigation, 28 candidate RNAs were identified. Following RTqPCR validation, the candidate RNAs were preliminarily evaluated in 15 samples to exclude miRNAs with low expression and high variation. Then, the expression levels of 10 relatively stable candidate reference RNAs in 100 samples were determined and further analysed using four commonly employed programs (geNorm, NormFinder, BestKeeper and ΔCq). According to the comprehensive stability rankings of the four algorithms, miR-320a-3p was validated as the most stable endogenous reference gene among the five forensically relevant body fluids, followed by miR-484, SNORD43, miR-320c and RNU6b. Moreover, the combined application of miR-320a-3p with RNU6b could increase the normalization effect. In addition, a total of 56 mock samples placed outdoors and indoors for different times were prepared to further evaluate the stability of candidate reference RNAs, and miR-320a-3p remained the preferred reference gene. Furthermore, the relative expression levels of publicly accepted body fluid-specific miRNAs were determined in 30 samples to verify the practicality and effectiveness of the reference genes. Our results revealed a set of alternative reference genes and could promote the development and application of miRNA-based body fluid identification by determining optional reference genes for strict normalization.

Effects of crime scene contaminants on surface-enhanced Raman analysis of hair

Forensic analysis of hair is important as hair is one of the most commonly examined forms of trace evidence found at crime scenes. A growing body of evidence suggests that surface-enhanced Raman spectroscopy (SERS), a label-free and non-destructive analytical technique, can be used to detect and identify artificial colorants present on hair. However, hair collected at crime scenes is often contaminated by substances of biological and non-biological origin present at such locations. In this study, we investigate the extent to which four contaminants, saliva, blood, dirt, and bleach can alter the accuracy of SERS-based detection and identification of both permanent and semi-permanent colorants present on hair. Our findings show that saliva and dirt reduce the intensity of the colorants' signals but do not obscure their detection and identification. At the same time, an exposure of the colored hair to bleach or the presence of blood eliminates SERS-based analysis of artificial dyes present on such samples. We identified the procedure that can be used to remove blood contamination, which, in turn, enables identification of the hair colorants on such pre-cleaned samples. However, bleach treatment irreversibly eliminates SERS-based detection of artificial colorants on hair. These findings expand our understandings about the potential of SERS in forensic investigation of colorants on trace hair evidence.

Do Circulating Redox Biomarkers Have Diagnostic Significance in Alcohol-Intoxicated People?

The toxic properties of ethanol are inextricably linked to oxidative stress. Despite many reports on the effects of alcohol dependence on blood redox homeostasis, there are no data on the oxidative stress profile in alcohol-poisoned cases. There are also no data on the diagnostic usefulness of redox biomarkers determined post-mortem in various biological fluids. This work investigates the utility of enzymatic and non-enzymatic antioxidant barrier, redox status, and oxidative/nitrosative stress biomarkers in different biological fluids (such as blood, urine, vitreous humor, and cerebrospinal fluid) in the post-mortem study of patients with acute alcohol intoxication. The study group included those who died due to acute ethanol intoxication (n = 22). The research showed a significant increase in glutathione peroxidase activity, total antioxidant status, ferric reducing antioxidant power, and tryptophan concentration only in the study group’s urine compared to the control. In other circulating fluids, both antioxidant enzyme activities and glycoxidation product concentrations were not significantly different in individuals who died of alcohol overdose compared with those who died suddenly. We also did not observe a connection between oxidation–reduction balance and the amount of alcohol consumed before death. These unexpected observations may be caused by irreversible post-mortem changes occurring at the cellular level due to autolysis and putrefaction. In summary, the use of circulating body fluids to assess redox homeostasis is limited in the post-mortem analysis. Our results indicate the increased stability of urine collected post mortem compared to other circulating bioliquids. Further studies are needed to assess the intensity of oxidative and carbonyl stress in ethanol-damaged organs and the effects of post-mortem processes on cellular redox balance.

A Comprehensive Characterization of Small RNA Profiles by Massively Parallel Sequencing in Six Forensic Body Fluids/Tissue

Body fluids/tissue identification (BFID) is an essential procedure in forensic practice, and RNA profiling has become one of the most important methods. Small non-coding RNAs, being expressed in high copy numbers and resistant to degradation, have great potential in BFID but have not been comprehensively characterized in common forensic stains. In this study, the miRNA, piRNA, snoRNA, and snRNA were sequenced in 30 forensic relevant samples (menstrual blood, saliva, semen, skin, venous blood, and vaginal secretion) using the BGI platform. Based on small RNA profiles, relative specific markers (RSM) and absolute specific markers (ASM) were defined, which can be used to identify a specific body fluid/tissue out of two or six, respectively. A total of 5204 small RNAs were discovered including 1394 miRNAs (including 236 novel miRNA), 3157 piRNAs, 636 snoRNAs, and 17 snRNAs. RSMs for 15 pairwise body fluid/tissue groups were discovered by differential RNA analysis. In addition, 90 ASMs that were specifically expressed in a certain type of body fluid/tissue were screened, among them, snoRNAs were reported first in forensic genetics. In brief, our study deepened the understanding of small RNA profiles in forensic stains and offered potential BFID markers that can be applied in different forensic scenarios.

Evaluations and comparisons of microbial diversities in four types of body fluids based on two 16S rRNA gene sequencing methods

BACKGROUND

Body fluids are one of the common biological traces at crime scenes. Understanding the types of these biological traces could provide key clues for the investigations of the forensic cases. In recent years, partial hypervariable regions of 16S rRNA gene sequencing and full-length 16S rRNA gene sequencing have attracted the interests of researchers and we intend to explore which method can be better applied to forensic researches.

METHODS

In this study, the 16S rRNA gene V3-V4 (short-read) sequencing based on next-generation sequencing and the full-length 16S rRNA gene sequencing based on single molecule real-time sequencing were used to classify microbes in saliva, peripheral blood, vaginal secretion and menstrual blood samples.

RESULTS

Alpha diversity metrics in short-read sequencing were larger than those of full-length sequencing. Phylum-level bacteria in four kinds of body fluids obtained from the two platforms were similar, while their abundances were different. The results of principal coordinates analysis and analysis of molecular variance indicated the microbial compositions of vaginal secretion and menstrual blood samples were similar, and the microbial compositions among saliva, peripheral blood, vaginal secretion or menstrual blood samples were significantly different. The linear discriminant analysis effect size showed the differential bacteria screened among the four kinds of body fluids were variant in two sequencing results.

CONCLUSION

Both sequencing methods could be used to detect bacterial diversities in four different types of body fluids and provide potential tools for microbes to identify the four kinds of body fluids in forensic investigation, in which full-length sequencing could provide more accurate taxonomy.

MicroRNAs: An Update of Applications in Forensic Science

MicroRNAs (miRNAs) are a class of non-coding RNAs containing 18–24 nucleotides that are involved in the regulation of many biochemical mechanisms in the human body. The level of miRNAs in body fluids and tissues increases because of altered pathophysiological mechanisms, thus they are employed as biomarkers for various diseases and conditions. In recent years, miRNAs obtained a great interest in many fields of forensic medicine given their stability and specificity. Several specific miRNAs have been studied in body fluid identification, in wound vitality in time of death determination, in drowning, in the anti-doping field, and other forensic fields. However, the major problems are (1) lack of universal protocols for diagnostic expression testing and (2) low reproducibility of independent studies. This review is an update on the application of these molecular markers in forensic biology.

A systematic analysis of miRNA markers and classification algorithms for forensic body fluid identification

Identifying the types of body fluids left at the crime scene can be essential to reconstructing the crime scene and inferring criminal behavior. MicroRNA (miRNA) molecule extracted from the trace of body fluids is one of the most promising biomarkers for the identification due to its high expression, extreme stability and tissue specificity. However, the detection of miRNA markers is not the answer to a yes-no question but the probability of an assumption. Therefore, it is a crucial task to develop complicated methods combining multi-miRNAs as well as computational algorithms to achieve the goal. In this study, we systematically analyzed the expression of 10 most probable body fluid-specific miRNA markers (miR-451a, miR-205-5p, miR-203a-3p, miR-214-3p, miR-144-3p, miR-144-5p, miR-654-5p, miR-888-5p, miR-891a-5p and miR-124-3p) in 605 body fluids-related samples, including peripheral blood, menstrual blood, saliva, semen and vaginal secretion. We introduced the kernel density estimation (KDE) method and six well-established methods to classify the body fluids in order to find the most optimal combinations of miRNA markers as well as the corresponding classifying method. The results show that the combination of miR-451a, miR-891a-5p, miR-144-5p and miR-203a-3p together with KDE can achieve the most accurate and robust performance according to the cross-validation, independent tests and random perturbation tests. This systematic analysis suggests a reference scheme for the identification of body fluids in an accurate and stable manner.