Establishing a minimum postmortem interval of human remains in an advanced state of skeletonization using the growth rate of bryophytes and plant roots

Forensic species identification: practical guide for animal and plant DNA analysis

The importance of non-human DNA in the forensic field has increased greatly in recent years, together with the type of applications. The molecular species identification of animal and botanical material may be crucial both for wildlife trafficking and crime scene investigation. However, especially for forensic botany, several challenges slow down the implementation of the discipline in the routine.Although the importance of molecular analysis of animal origin samples is widely recognized and the same value is acknowledged to the botanical counterpart, the latter does not find the same degree of application.The availability of molecular methods, especially useful in cases where the material is fragmented, scarce or spoiled preventing the morphological identification, is not well known. This work is intended to reaffirm the relevance of non-human forensic genetics (NHFG), highlighting differences, benefits and pitfalls of the current most common molecular analysis workflow for animal and botanical samples, giving a practical guide. A flowchart describing the analysis paths, divided in three major working areas (inspection and sampling, molecular analysis, data processing and interpretation), is provided. More real casework examples of the utility of non-human evidence in forensic investigations should be shared by the scientific community, especially for plants. Moreover, concrete efforts to encourage initiatives in order to promote quality and standardization in the NHFG field are also needed.

Using plants in forensics: State-of-the-art and prospects

The increasing use of plant evidence in forensic investigations gave rise to a powerful new discipline - Forensic Botany - that analyses micro- or macroscopic plant materials, such as the totality or fragments of an organ (i.e., leaves, stems, seeds, fruits, roots) and tissue (i.e., pollen grains, spores, fibers, cork) or its chemical composition (i. e., secondary metabolites, isotopes, DNA, starch grains). Forensic botanists frequently use microscopy, chemical analysis, and botanical expertise to identify and interpret evidence crucial to solving civil and criminal issues, collaborating in enforcing laws or regulations, and ensuring public health safeguards. The present work comprehensively examines the current state and future potential of Forensic Botany. The first section conveys the critical steps of plant evidence collection, documentation, and preservation, emphasizing the importance of these initial steps in maintaining the integrity of the items. It explores the different molecular analyses, covering the identification of plant species and varieties or cultivars, and discusses the limitations and challenges of these techniques in forensics. The subsequent section covers the diversity of Forensic Botany approaches, examining how plant evidence exposes food and pharmaceutical frauds, uncovers insufficient or erroneous labeling, traces illegal drug trafficking routes, and combats the illegal collection or trade of protected species and derivatives. National and global security issues, including the implications of biological warfare, bioterrorism, and biocrime are addressed, and a review of the contributions of plant evidence in crime scene investigations is provided, synthesizing a comprehensive overview of the diverse facets of Forensic Botany.

Forensic botany: who?, how?, where?, when?

Plants are a good source of biological forensic evidence; this is due to their ubiquity, their ability to collect reference material, and their sensitivity to environmental changes. However, in many countries, botanical evidence is recognised as being scientifically. Botanical evidence is not mostly used for perpertration, instead it tends to serve as circumstantial evidence. Plant materials constitute the basis, among others, for linking a suspect or object to a crime scene or a victim, confirming or not confirming an alibi, determining the post-mortem interval, and determining the origin of food/object. Forensic botany entails field work, knowledge of plants, understanding ecosystem processes, and a basis understaning of geoscience. In this study, experiments with mammal cadavers were conducted to determine the occurence of an event. The simplest criterion characterising botanical evidence is its size. Therefore, macroremains include whole plants or their larger fragments (e.g. tree bark, leaves, seeds, prickles, and thorns), whereas microscopic evidence includes palynomorphs (spores and pollen grains), diatoms, and tissues. Botanical methods allow for an analysis to be repeated multiple times and the test material is easy to collect in the field. Forensic botany can be supplemented with molecular analyses, which, although specific and sensitive, still require validation.

When time is not of the essence: constraints to the carbon balance of bryophytes

The data available so far indicate that the photosynthetic and relative growth rates of bryophytes are 10% of those reported for tracheophytes. By examining the existing literature and reanalysing data published in over 100 studies, this review examines the ecophysiological, biochemical, and structural reasons behind this phenomenon. The limiting Rubisco content and surface for gas exchange are the internal factors that can explain the low photosynthetic and growth rates of bryophytes. The role of the thicker cell walls of bryophytes in limiting CO2 diffusion is unclear, due to the current uncertainties regarding their porosity and permeability to CO2. From this review, it is also evident that, despite bryophytes having low photosynthetic rates, their positive carbon balance is tightly related to their capacity to deal with extreme conditions. Contributing factors include their capacity to deal with large daily temperature oscillations, and their capacity to delay the cessation of photosynthesis under water deficit (or to tolerate desiccation in extreme situations). Although further studies on bryophytes are needed before more solid conclusions can be drawn, it seems that their success relies on their remarkable tolerance to a highly variable environment, possibly at the expense of their maximum photosynthetic rate.

Forensic botany: time to embrace natural history collections, large scale environmental data and environmental DNA

Forensic botany is a diverse discipline that spans many aspects of plant sciences, particularly taxonomy, field botany, anatomy, and ecology. Internationally, there is a significant opportunity to expand the application of forensic botany in criminal investigations, especially war crimes, genocide, homicide, sexual violence, serious physical assault, illegal trade in endangered species and wildlife crime. In civil proceedings, forensic botany may, for example, be called upon in trade disputes such as accidental contamination of commodities. Despite the potential, there are barriers to the wider application of forensic botany in criminal cases; there is a widespread need to improve the efficiency of botanical trace evidence identification. This could partly be addressed by embracing innovations in image recognition and by accessing the huge quantity of specimens and images housed in natural history collections worldwide. Additionally, the recent advances in DNA sequencing technologies and the expansion of environmental DNA (eDNA) and forensic ecogenomics, offers opportunities to more rapidly provide species-level identifications. The impact of taphonomic processes upon vegetation, and vice versa, remains poorly understood; improved understanding of these interactions and their ecological impacts may be invaluable in improving clandestine burial search protocols.

Microbiomes in forensic botany: a review

Fragments of botanical material can often be found at crime scenes (on live and dead bodies, or on incriminating objects) and can provide circumstantial evidence on various aspects of forensic investigations such as determining crime scene locations, times of death or possession of illegal species. Morphological and genetic analysis are the most commonly applied methods to analyze plant fragment evidence but are limited by their low capacity to differentiate between potential source locations, especially at local scales. Here, we review the current applications and limitations of current plant fragment analysis for forensic investigations and introduce the potential of microbiome analysis to complement the existing forensic plant fragment analysis toolkit. The potential for plant fragment provenance identification at geographic scales meaningful to forensic investigations warrants further investigation of the phyllosphere microbiome in this context. To that end we identify three key areas of future research: 1) Retrieval of microbial DNA of sufficient quality and quantity from botanical material; 2) Variability of the phyllosphere microbiome at different taxonomic and spatial scales, with explicit reference to assignment capacity; 3) Impacts on assignment capacity of time, seasonality and movement of fragments between locations. The development of robust microbiome analysis tools for forensic purposes in botanical material could increase the evidentiary value of the botanical evidence commonly encountered in casework, aiding in the identification of crime scene locations.

Common and much less common scenarios in which botany is crucial for forensic pathologist and anthropologists: a series of eight case studies

It is commonly accepted that crime scene recovery and recording are key moments of any judicial inspection in which investigators must decide on the correct strategies to put into place. Complex outdoor scenarios, presenting partially or entirely skeletonised remains, can benefit more than others by the intervention of environmental specialists (forensic anthropologists, archaeologists, entomologists and botanists). These experts are capable of singling out, correctly recording and recovering environmental evidence that can lead to a more comprehensive reconstruction of a given criminal episode. If human remains are discovered in an outdoor scenario, the on-site presence of a botanist will guarantee a correct approach to the identification, recording and recovery of any botanical evidence. If an on-site botanist is not available, the operators must be capable of both the botanical evaluation of a scene and the implementation of correct botanical sampling protocols.

The following collection of unusual case histories that aim at underlining the efficacy of forensic botany will examine the determination of post mortem or the post depositional interval, evidence for a victim’s post mortem transfer, evidence for the identification of a primary crime scene and evidence for the identification of a victim’s dismemberment site. In another two cases, one, we will illustrate the important role that forensic botany played in the discrimination between botanical material used to voluntarily conceal a victim and vegetation that had grown naturally above a disposal site, whereas the other will highlight the protocols implemented for the identification of a murder weapon.

Contribution of plant anatomy to forensic investigation: Tree bark morphology

Plant science has been more and more utilized in forensic investigation, although its full potential is still to be reached. Plant macroremains are a powerful tool to link a body or other evidence back to a primary crime scene as they can provide detailed information about its previous ecological and geographic location. However, plant macroremains are often poorly preserved and difficult to identify, as diagnostic elements are seldom present within the assemblage occurring on the scene. Plant fragments most likely to be found are those exposed to the environment and resistant to degradation. The bark of woody plants meets these requirements but the possibility of its identification at species level from small fragments is not known. Starting from a real homicide case, where bark splinters were found on the victim, we aimed to assess the forensic potential of bark identification from small fragments like those likely to occur on a crime scene. Two identification keys were prepared for 16 common lowland tree species from Northern Italy; one key used all the available anatomical traits, the second only those from the outer bark. The second key was not able to discriminate some couples of species unambiguously, but could identify the bark fragments of the homicide as Robinia pseudoacacia, as confirmed from direct comparison with a reference sample. Bark fragments deserve to be included into the macroremains to be analyzed during an investigation, but small samples could easily lack diagnostic traits, and the building of a reference collection should be encouraged.

Forensic genetics and genomics: Much more than just a human affair

While traditional forensic genetics has been oriented towards using human DNA in criminal investigation and civil court cases, it currently presents a much wider application range, including not only legal situations sensu stricto but also and, increasingly often, to preemptively avoid judicial processes. Despite some difficulties, current forensic genetics is progressively incorporating the analysis of nonhuman genetic material to a greater extent. The analysis of this material-including other animal species, plants, or microorganisms-is now broadly used, providing ancillary evidence in criminalistics in cases such as animal attacks, trafficking of species, bioterrorism and biocrimes, and identification of fraudulent food composition, among many others. Here, we explore how nonhuman forensic genetics is being revolutionized by the increasing variety of genetic markers, the establishment of faster, less error-burdened and cheaper sequencing technologies, and the emergence and improvement of models, methods, and bioinformatics facilities.

Accurate predictions of postmortem interval using linear regression analyses of gene meter expression data

In criminal and civil investigations, postmortem interval is used as evidence to help sort out circumstances at the time of human death. Many biological, chemical, and physical indicators can be used to determine the postmortem interval - but most are not accurate. Here, we sought to validate an experimental design to accurately predict the time of death by analyzing the expression of hundreds of upregulated genes in two model organisms, the zebrafish and mouse. In a previous study, the death of healthy adults was conducted under strictly controlled conditions to minimize the effects of confounding factors such as lifestyle and temperature. A total of 74,179 microarray probes were calibrated using the Gene Meter approach and the transcriptional profiles of 1063 genes that significantly increased in abundance were assembled into a time series spanning from life to 48 or 96h postmortem. In this study, the experimental design involved splitting the transcription profiles into training and testing datasets, randomly selecting groups of profiles, determining the modeling parameters of the genes to postmortem time using over- and/or perfectly-defined linear regression analyses, and calculating the fit (R²) and slope of predicted versus actual postmortem times. This design was repeated several thousand to million times to find the top predictive groups of gene transcription profiles. A group of eleven zebrafish genes yielded R² of 1 and a slope of 0.99, while a group of seven mouse liver genes yielded a R² of 0.98 and a slope of 0.97, and seven mouse brain genes yielded a R² of 0.95 and a slope of 0.87. In all cases, groups of gene transcripts yielded better postmortem time predictions than individual gene transcripts. The significance of this study is two-fold: selected groups of gene transcripts provide accurate prediction of postmortem time, and the successfully validated experimental design can now be used to accurately predict postmortem time in cadavers.

RNA degradation as described by a mathematical model for postmortem interval determination

Precisely determining the postmortem interval (PMI) is crucial to civil, criminal and forensic cases. A technique to exploit the postmortem RNA transcript level was developed to increase the accuracy and practicality of PMI estimation. For this purpose, lung tissues and muscle tissues were removed at twelve time points (0-144 h) from rat corpses that had been stored at three different temperatures (10, 20 and 30 °C). Human tissues were collected at autopsy from twelve real cases with known PMI values and other parameters. After the RNA was extracted from all these samples, the transcript levels of nine biomarkers were analyzed by real-time quantitative PCR (RT-qPCR). With the assistance of geNorm, miR-195, miR-200c, 5S, U6 and RPS29 were selected as reference biomarkers for lung specimens; miR-1, miR-206, 5S and RPS29 were chosen as control markers for muscle tissues. On the contrary, ACTB and GAPDH were significantly correlated with the PMI. The mathematical models using these target biomarkers were constructed to describe the characteristic relationship between △Ct values (normalized to reference biomarkers) and the observed PMI for each temperature group. Following validation, the relatively low error rates (7.4% and 12.5% for rat and human samples, respectively) demonstrated the accuracy and reliability of the mathematical model. We believe these results indicate that the multi-parametric mathematical model can become a practical tool for PMI estimation.

The selection of endogenous genes in human postmortem tissues

Precisely determining the postmortem interval (PMI), which is crucial to criminal and forensic cases, is a research in which quantitative RT-PCR (also known as qRT-PCR or real-time RT-PCR) has been used to analyse gene expression levels and data normalisation should be required to eliminate the differences among the samples. Therefore, it is quite necessary to find stable molecular biological markers in PMI determination research. In this study, we compared nine commonly used endogenous markers (containing ACTB, GAPDH, B2M, U6, 18S rRNA, hsa-mir-1, hsa-mir-9, hsa-mir-194-1 and hsa-mir-203) in the 109 human tissue samples obtained from autopsy at the aim of finding stable markers in human tissues with consideration of the impact of parameters (PMI and cause of death). After RNA was extracted from four tissues (heart, brain, kidney, skin), the Ct values of nine endogenous markers were obtained by qRT-PCR and assessed by geNorm software. The results showed that U6, GAPDH and 18S rRNA were the suitable markers in our set of samples in various corpse conditions, that B2M and ACTB were reliable internal controls in heart tissue only, and that microRNAs had such high M values that they should not be chosen for endogenous control genes.

Genus identification of toxic plant by real-time PCR

Some plants have toxicities that are dangerous for humans. In the case of poisoning by toxic plants, a rapid and easy screening test is required for accurate medical treatment or forensic investigation. In this study, we designed specific primer pairs for identification of toxic plants, such as subgenus Aconitum, genus Ricinus, genus Illicium, and genus Scopolia, by internal transcribed spacer sequences of nuclear ribosomal DNA. Allied species of target plants, foods, and human DNA were not detected, but each primer pair provided a specific PCR product from the target plant using real-time PCR. This method can detect the subgenus Aconitum, genus Ricinus, and genus Scopolia with template DNA of 10 pg, respectively, and genus Illicium with 1 pg. Furthermore, each primer pair provided the exact PCR product from digested target plants in artificial gastric fluid. When a trace unknown plant sample in forensic investigation is collected from stomach contents, this PCR assay may be useful for screening toxic plants.