Luminol and the postmortem interval estimation - influence of taphonomic factors.

The estimation of the postmortem interval (PMI) is one of the key challenges for forensic anthropologists. Although there are several methods referenced for this purpose, none is sufficiently effective. One of the main reasons justifying the complexity of this task is the influence of several taphonomic factors.The study of the Luminol technique has stood out as a promising method for estimating PMI, complementing the existing methods, since it is an economic, easy and reproducible method that operates as a presumptive test. However, it is not known which taphonomic factors can influence the results obtained by this technique.The aim of this study is to test the influence of taphonomic factors, such as temperature, humidity, soil type and pH, on the estimation of the PMI by the Luminol technique.In order to test the influence of the referred factors, a sample consisting of 30 clavicles, with known and similar PMI, collected from autopsies, was distributed as evenly as possible by six vases and buried with different decomposition conditions for a period of 12 months. After the exhumation and sample preparation, the Luminol technique was applied.It was possible to clearly observe differences in the results. Thus, according to our research, it is possible to conclude that the results obtained by the application of Luminol are influenced by taphonomic factors. Therefore, the context in which a body is found should always be considered for applying this technique.

Forensic taphonomic experimental design matters: a study assessing clothing and carrion biomass load on scavenging in Cape Town, South Africa.

The identification of unknown human remains is a significant and ongoing challenge in South Africa, worsened by the country's high murder rate. The rate of decomposition in South Africa is significantly influenced by vertebrate scavenging, which, if not considered, can impede the accurate estimation of the post-mortem interval. Scavenging patterns vary greatly depending on the environment and ecological region, and there is limited data for the Western Cape province. To address this gap, two clothed and uncaged pig carcasses weighing 60 kg each were placed in the field in July 2021 and January 2022, respectively. Motion-activated infrared-capable trail cameras were used to observe decomposition, scavenger species, and their activities. Additionally, a comparative sample of 16 unclothed carcasses deployed between 2014 and 2016 in the same habitat were analyzed to assess the impact of clothing and biomass load. The study found three main results: (1) Regardless of habitat or biomass load, it took significantly less time to reach decomposition milestones (25%, 50%, and 75%) during the summer season; (2) the presence of mongoose scavengers had a greater impact on the time required to reach milestones during winter compared to summer; and (3) single carcass deployments reached the milestones faster than multi-carcass deployments in both seasons. This research highlights the potential inaccuracy of current methods for estimating the post-mortem interval when scavenging activity is not considered or documented in the underlying experimental data, particularly for environments or ecological biomes where scavengers actively impact decomposition rates.

Postmortem CT analysis of paranasal sinuses using an experimental model of drowning.

Fluid-filled paranasal sinuses are suggested to be a valuable tool to distinguish between drowning and non-drowning postmortem, yet the mechanisms governing fluid entry remains unknown. We investigate if fluid-filled paranasal sinuses are caused by a passive influx from submersion or an active aspiration mechanism during drowning. The ovine nasal cavity and maxillary sinuses are remarkably similar anatomically to humans, and have been used for endoscopic surgical training in recent decades. We submerged 15 decapitated ovine heads from agricultural waste at a depth of 2 m in flowing water for 1, 8, and 24 h and 7 days. Paranasal sinuses were CT imaged and compared pre- and post-submersion to non-submerged controls. Furthermore, we examined the paranasal sinuses of a single homicide case of a non-drowned submerged subject. Results demonstrate that fluid passively enters the maxillary sinus postmortem in the non-drowned ovine heads following 1 h of submersion. Fluid volume was independent of submersion time and influenced by time out of water as well as handling, since volume was reduced between consecutive CT scans. In contrast to our hypothesis, the filling of the paranasal sinuses is due to passive influx of fluid from submersion rather than an active aspiration during drowning. The observation that paranasal sinuses were fluid-filled in a single medico-legal case of postmortem submersion supports the finding of passive influx. Consequently, careful interpretation of fluid-filled paranasal sinuses is required when bodies are found in water, as the finding cannot distinguish between postmortem submersion and drowning.

Subject-specific finite element head models for skull fracture evaluation-a new tool in forensic pathology.

Post-mortem computed tomography (PMCT) enables the creation of subject-specific 3D head models suitable for quantitative analysis such as finite element analysis (FEA). FEA of proposed traumatic events is an objective and repeatable numerical method for assessing whether an event could cause a skull fracture such as seen at autopsy. FEA of blunt force skull fracture in adults with subject-specific 3D models in forensic pathology remains uninvestigated. This study aimed to assess the feasibility of FEA for skull fracture analysis in routine forensic pathology. Five cases with blunt force skull fracture and sufficient information on the kinematics of the traumatic event to enable numerical reconstruction were chosen. Subject-specific finite element (FE) head models were constructed by mesh morphing based on PMCT 3D models and A Detailed and Personalizable Head Model with Axons for Injury Prediction (ADAPT) FE model. Morphing was successful in maintaining subject-specific 3D geometry and quality of the FE mesh in all cases. In three cases, the simulated fracture patterns were comparable in location and pattern to the fractures seen at autopsy/PMCT. In one case, the simulated fracture was in the parietal bone whereas the fracture seen at autopsy/PMCT was in the occipital bone. In another case, the simulated fracture was a spider-web fracture in the frontal bone, whereas a much smaller fracture was seen at autopsy/PMCT; however, the fracture in the early time steps of the simulation was comparable to autopsy/PMCT. FEA might be feasible in forensic pathology in cases with a single blunt force impact and well-described event circumstances.

Postmortem Computed Tomography Is a Reliable, Reproducible, and Accurate Method in Measuring Body Length.

ABSTRACT: Currently, traditional body length measurement at postmortem analysis involves processes, which are susceptible to human error and not reviewable or reproducible in case of data loss. Many facilities are now adopting routine postmortem computed tomography (PMCT) scanning, which provides a permanent and reviewable radiological record of body dimensions. Previous literature has validated the use of PMCT in estimating body and organ weights, but not in body length measurement. This retrospective study aimed to determine whether body length can be accurately and reliably measured when compared with traditional measurements in 50 consecutive adult cases. Our findings revealed that body length measured using PMCT had high intrarater and interrater reliability across different experience levels in raters (Pearson correlation coefficient and interclass correlation: >0.99, P < 0.01). Although body lengths measured using PMCT were significantly shorter (mean, -1.2 cm; 95% confidence interval, -1.75 to -0.65 cm; P < 0.05), it was deemed clinically insignificant and correlated well with those measured at postmortem examination (Pearson correlation coefficient and interclass correlation, >0.97; P < 0.01). While care will need to be taken to ensure the body in the body bag is in reasonable anatomical position for scanning purposes, overall, body length measured uniform PMCT is reliable, reproducible, and accurate.

A Narrative Review on the Clinical Relevance of Imaging the Circumventricular Brain Organs and Performing Their Anatomical and Histopathological Examination in Acute and Postacute COVID-19.

ABSTRACT: Autopsy followed by histopathological examination is foundational in clinical and forensic medicine for discovering and understanding pathological changes in disease, their underlying processes, and cause of death. Imaging technology has become increasingly important for advancing clinical research and practice, given its noninvasive, in vivo and ex vivo applicability. Medical and forensic autopsy can benefit greatly from advances in imaging technology that lead toward minimally invasive, whole-brain virtual autopsy. Brain autopsy followed by histopathological examination is still the hallmark for understanding disease and a fundamental modus operandi in forensic pathology and forensic medicine, despite the fact that its practice has become progressively less frequent in medical settings. This situation is especially relevant with respect to new diseases such as COVID-19 caused by the SARS-CoV-2 virus, for which our neuroanatomical knowledge is sparse. In this narrative review, we show that ad hoc clinical autopsies and histopathological analyses combined with neuroimaging of the principal circumventricular organs are critical to gaining insight into the reconstruction of the pathophysiological mechanisms and the explanation of cause of death (ie, atrium mortis) related to the cardiovascular effects of SARS-CoV-2 infection in forensic and clinical medicine.

[Is this iatrogenic pathology or rare disease?] / Yatrogennaya patologiya ili redkaya bolezn'?

The article is devoted to the problem of diagnosis and treatment strategy of Buerger's disease rarely found in the expert and clinical practice, that is inflammatory disease of unknown etiology, affecting mainly small and medium arteries and veins of limbs. Vascular surgeons around the world have been solving this problem for many years, both in terms of timely diagnosis of this disease and its proper pathogenic treatment. The authors of the article described an expert case of Buerger's disease larvated course in 15-years-old girl, which primarily was mistakenly assessed by specialists as iatrogenic pathology of right forearm vessels in injecting aminazin solution that, according to the clinicians' opinion, led to dry gangrene formation of right wrist and its subsequent amputation. The results of the forensic histological study and retrospective analysis of all child's medical documents allowed to correctly diagnose this rare pathology but only on the stage of commission forensic medical examination in the framework of the initiated criminal proceeding against several leading medical organizations in Saint-Petersburg with a pediatric profile. The authors noted the role of routine medical manipulation in manifestation of larvated pathologic process in a teenage girl in addition to full health and well-being. The objective of present article is devoted to understanding this problem.

[Diagnostic criteria of death cause from low temperature in air and water established by traditional expert examination methods]. / Diagnosticheskie kriterii prichiny smerti ot deistviya nizkoi temperatury na vozdukhe i v vode, ustanavlivaemye s pomoshch'yu traditsionnykh metodov ekspertnogo issledovaniya.

Death from general hypothermia is one of the leading causes in the structure of violent death in the Russian Federation. OBJECTIVE: To clarify and supplement the complex of differential diagnostic macro- and microscopic signs of a fatal acute general cold trauma received when person is in the air and water. MATERIAL AND METHODS: The conclusions of forensic medical experts on the bodies of people who died from hypothermia in the air and in water (by 150 observations) were analyzed. Methods of descriptive statistics, calculation of the frequency ratio of signs' occurrence were used. RESULTS: The article provides quantitative assessment of occurrence (detection) rate of diagnostically significant signs established with the help of traditional methods of expert examination. A new classification of diagnostic death signs from hypothermia taking into account their differential diagnostic significance and reflecting the conditions of a person's stay in the air and water in the pre-mortem and post-mortem periods, as well as terminal period mechanisms is proposed. CONCLUSION: The established complexes of signs provide an objective basis for determining death cause in non-obvious conditions when cold exposure is expected to be one of the most damaging factors.

Validation and optimization of the diatom L/D ratio as a diagnostic marker for drowning.

If a dead body is discovered in water, it nearly always raises the question about the cause of death, often associated with the persistent problem to differentiate between a drowning incident and post-mortem immersion. In numerous cases, a reliable confirmation of death by drowning is often only possible by a combination of diagnoses obtained from autopsy and additional investigations. As to the latter, the use of diatoms has been suggested (and debated) since decades. Based on the consideration that diatoms are present in almost every natural waterbody and are unavoidably incorporated when water is inhaled, their presence in the lung and other tissues can provide evidence of drowning. However, the traditional diatom test methods are still subject of controversial discussion and suspected of erroneous outcome, predominantly through contamination. A promising alternative to minimize the risk of erroneous outcome seems to be disclosed by the recently suggested MD-VF-Auto SEM technique. Especially the establishment of a new diagnostic marker (L/D ratio), which represents the factorial proportion between the diatom concentration in lung tissue and the drowning medium, allows for clearer distinction of drowning and post-mortal immersion and is largely robust to contamination. However, this highly elaborated technique requires specific devices which are frequently unavailable. We therefore developed a modified method of SEM-based diatom testing to enable the use on more routinely available equipment. Process steps such as digestion, filtration, and image acquisition were thoroughly broken down, optimized, and ultimately validated in five confirmed drowning cases. Taking certain limitations into consideration, L/D ratio analysis provided promising results, even in cases of advanced decomposition. We conclude that our modified protocol indeed opens a way for a broader use of the method in forensic drowning investigation.

Assessing wound vitality in decomposed bodies: a review of the literature.

The capability of discriminating between a vital and a post-mortem injury has always been a central theme in forensic pathology, particularly when the corpse is an advanced state of decomposition. Post-mortem decay of the body can mask or disrupt the classical features of a skin lesion, making it difficult to establish the cause and manner of death. Taphonomically challenging situations pose several interpretative issues of skin lesions which need to be addressed with scientifically recent methods that are still limited in the forensic literature. For that reason, the present research aims at resuming what is currently available in the attempt to provide some insight regarding this topic. This review considers only original researches, in which the markers of vitality were studied a significant amount of time after death, in order to test post-mortem persistency of these markers over time. A number of 132 original articles and reviews were considered, and the most significant results are resumed in an overview table and in two intuitive figures. Though many researchers tried to establish the vitality of lesions in specimen, few analysed samples from bodies when a significant degree of putrefaction or burning had occurred. The most significant marker proved to be GPA, which sowed a satisfying persistence over time (up to 6 months in air putrefaction and 15 days in water). However, what clearly emerged is that further studies are needed to address the challenges of taphonomically transformed specimen and to possibly neutralize the variability of experimental conditions, which affect the reproducibility of results. In conclusion, this study could be a starting point for providing food for thoughts about the most useful markers to search for in unusually tricky autopsy cases.

Suspension-associated dislocation of the jaw in hanging.

Hanging is a common type of death, and the role of the medical investigation of such deaths by a forensic pathologist not only requires the determination of the cause of death but providing information to assist in the determination of the manner of death. The forensic pathologist should be well versed in the spectrum of injuries known to be associated with neck compression, to document injuries known to be associated with hanging, but also to identify those that are inconsistent with self-inflicted hanging or that may suggest the involvement of a third party in the death. Comprehensive identification and correct interpretation of external and internal injury are crucial for the appropriate degree of police and coroner/medical examiner investigation. We present two cases of deaths believed to be caused by self-inflicted hanging that were observed to have unexpected unilateral dislocation of the temporomandibular joint identified on routine post-mortem computed tomography, without any evidence of involvement of a third party. This injury was unexplained and had not been previously observed at our Forensic Institute nor was it identified after a review of the published biomedical research literature. Issues regarding the cause of this abnormality, possible mechanisms, and the medicolegal significance of this finding will be discussed.

Forensic post-mortem CT in children.

Post-mortem computed tomography (PMCT) imaging is gaining popularity and acceptance for use alongside forensic autopsies of children, predominantly to aid in the detection of traumatic injuries. Recent research on this topic has provided a breadth of new information regarding the appropriate usage, imaging guidance, and diagnostic accuracy for the identification of different paediatric pathologies. Additionally, advanced CT imaging techniques, such as PMCT angiography or ventilated PMCT, have been trialled, and post-mortem micro-CT is now being used in specialist centres for the assessment of subtle fractures in extracted bone specimens. Various image post-processing methods (e.g., three-dimensional printing from PMCT imaging data) are being used for the illustration of injuries in the medicolegal setting to a lay audience and provide another avenue for the future of forensic radiology research. In this review, the evidence-based principles and benefits of post-mortem imaging for forensic investigation in childhood deaths are presented, with a particular focus on PMCT and current practices. Variations in forensic imaging strategies around the world, published diagnostic accuracy rates, and expected normal post-mortem imaging findings are discussed, as well as potential future applications and research in this area.

Impact of changing from autopsy to post-mortem CT in an entire HM Coroner region due to a shortage of available pathologists.

A significant problem facing routine medicolegal coroner-referred autopsies is a shortfall of pathologists prepared to perform them. This was particularly acute in Lancashire, where the coroner decided to initiate a service that relied on post-mortem computed tomography (PMCT). This involved training anatomical pathology technologists (APTs) to perform external examinations, radiographers to perform scans, and radiologists to interpret them. The service started in 2018 and now examines over 1,500 cases per year. This study outlines the PMCT process using NHS staff, with CT equipment and logistics managed by the commercial sector. It compares the demographics and outcomes of PM investigations for two 6-month periods: the autopsy service prior to 2018, and then the PMCT service. These data were then compared with previous UK PMCT data. Referrals for adult non-suspicious deaths were made in 913 cases of which 793 (87%) had PMCT between 01/10/2018 and 31/03/2019. Fifty-six cases had autopsy after PMCT, so 81% of cases potentially avoided autopsy. The PMCT service did not delay release of bodies to the next-of-kin. Comparing the cause of death given shows no difference in the proportions of natural and unnatural deaths. There was an increase in diagnosis of coronary artery disease for PMCT, with less respiratory diagnoses, a feature not previously demonstrated. These data suggest PMCT is a practical solution for potentially failing autopsy services. By necessity, this involves changes in diagnoses, as PMCT and autopsy have different strengths and weakness, but the ability to pick up unnatural death appears unaffected.

Post-mortem CT in the investigation of homicides.

AIM: To investigate the reliability of post-mortem computed tomography (PMCT) in a case series of homicides involving blunt-force, sharp-force, and ballistic trauma. MATERIALS AND METHODS: The study investigates 16 homicide cases that underwent PMCT before autopsy. Two radiologists assessed the PMCT examinations and the data were compared to the forensic pathology findings. Data were organised in broad categories: foreign bodies, external injuries, soft-tissue and organ injuries, fractures, air in cavities, fluid collections, random pathology, and wound track. Findings were organised by systems: head and neck, thorax, abdomen and pelvis, extremities. Cohen's kappa statistics were used to assess observer agreement. RESULTS: Six gunshot-related homicides (37.5%), seven sharp-force-related homicides (43.75%), two blunt-force-related deaths (12.5%), and one homicide due to mechanical asphyxia (1.25%) were analysed. A total of 64 fractures were reported by the pathologists, 67 by radiologist 1 and 68 by radiologist 2. Agreement was deemed substantial in all cases. Pathologists failed to report gas in cavities while radiologists underreported superficial injuries. CONCLUSION: An overall observation was that less accurate findings were produced by the blinded radiologist in comparison to the non-blinded one. The extremeness of homicides obscured the interpretation of PMCT leading to the observed discrepancies. The combination of PMCT and autopsies is deemed optimal when investigating homicidal events.

Deep Learning-Based Diagnosis of Fatal Hypothermia Using Post-Mortem Computed Tomography.

In forensic medicine, fatal hypothermia diagnosis is not always easy because findings are not specific, especially if traumatized. Post-mortem computed tomography (PMCT) is a useful adjunct to the cause-of-death diagnosis and some qualitative image character analysis, such as diffuse hyperaeration with decreased vascularity or pulmonary emphysema, have also been utilized for fatal hypothermia. However, it is challenging for inexperienced forensic pathologists to recognize the subtle differences of fatal hypothermia in PMCT images. In this study, we developed a deep learning-based diagnosis system for fatal hypothermia and explored the possibility of being an alternative diagnostic for forensic pathologists. An in-house dataset of forensic autopsy proven samples was used for the development and performance evaluation of the deep learning system. We used the area under the receiver operating characteristic curve (AUC) of the system for evaluation, and a human-expert comparable AUC value of 0.905, sensitivity of 0.948, and specificity of 0.741 were achieved. The experimental results clearly demonstrated the usefulness and feasibility of the deep learning system for fatal hypothermia diagnosis.

Comparison of fatal traumatic medico-legal cases with postmortem computed tomography and autopsy: A pilot study in Taiwan.

In order to determine the performance of postmortem computed tomography (PMCT) in identifying traumatic-relevant macroscopic findings in medico-legal cases, this retrospective observational pilot study involving nine trauma casualties who had received PMCT prior to autopsy. The comparison of these findings in six anatomical regions as dictated in Injury Severity Score (ISS) were performed. 104 traumatic-relevant findings were identified with achievement of 51% congruent findings. PMCT and autopsy had additionally found 22 and 29 findings respectively. PMCT had highest sensitivity for extremity injury (81.82%), followed by chest (73.91%), head, neck and face (71.43%), and abdomino-pelvic area (50%). It had excellent detection rate in abnormal air collection, fracture, foreign body localization, internal ballistic and intracranial pathology. However, the solid organ and vascular injuries as well as integumentary lesions were the major drawback. In conclusion, incorporation of PMCT to autopsy in medico-legal investigation helps to preserve the most abundant traumatic-relevant injuries compared to either modality.

Forensic Proteomics for the Discovery of New post mortem Interval Biomarkers: A Preliminary Study.

Estimating the time since death (post mortem interval, PMI) represents one of the most important tasks in daily forensic casework. For decades, forensic scientists have investigated changes in post mortem body composition, focusing on different physical, chemical, or biological aspects, to discover a reliable method for estimating PMI; nevertheless, all of these attempts remain unsuccessful considering the currently available methodical spectrum characterized by great inaccuracies and limitations. However, recent promising approaches focus on the post mortem decomposition of biomolecules. In particular, significant advances have been made in research on the post mortem degradation of proteins. In the present study, we investigated early post mortem changes (during the first 24 h) in the proteome profile of the pig skeletal muscle looking for new PMI specific biomarkers. By mass spectrometry (MS)-based proteomics, we were able to identify a total of nine potential PMI biomarkers, whose quantity changed constantly and progressively over time, directly or inversely proportional to the advancement of post mortem hours. Our preliminary study underlines the importance of the proteomic approach in the search for a reliable method for PMI determination and highlights the need to characterize a large number of reliable marker proteins useful in forensic practice for PMI estimation.

Taphonomic study on drowned victims in a non-sequestered aquatic environment in the Mediterranean Sea.

Human decomposition in sea water poses several challenges to forensic practitioners tasked with the analysis of drowned bodies. Postmortem changes in the marine environment have not been extensively investigated and the current literature is mainly based on bodies retrieved from shallow waters or on limited samples. On 18 April 2015, a fishing boat carrying allegedly 1,000 migrants sank in the Mediterranean Sea. In a fifteen-month time span, humanitarian missions were carried out to recover the bodies from the sea. The present study investigates postmortem changes on the drowned victims in a non-sequestered environment in the Mediterranean Sea. A retrospective study was performed by two observers on the autopsy photographic records in the series of bodies recovered from the open sea. For 184 bodies, the postmortem changes were evaluated according to facial, body, limb, and total aquatic decomposition score (FADS, BADS, LADS, TADS, respectively). Furthermore, a modification to the current scoring system that divides upper and lower limbs was suggested. The interobserver agreement was assessed using Krippendorff's alpha coefficient. Possible relations between the decomposition scores and PMSI were investigated with Pearson correlation analysis. According to the sequence of the recovery missions, increasing FADS, BADS, LADS, and TADS were observed. The modified scoring system showed a strong agreement between observers, allowing a more accurate description of the actual extent of decomposition. The scores showed a significant relation with the PMSI (p < 0.01). Prolonged submersion in the open marine environment was confirmed to show increasing decomposition rates, from moderate decay to full disarticulation. This study provides a descriptive unicum of the postmortem changes in the open sea, which may contribute to strengthen the discipline and aid description of bodies recovered in similar circumstances, especially if a body needs to be associated to a disaster or period with respect to another, thus facilitating families or authorities in the search for specific victims.

The role of PMCT for the assessment of the cause of death in natural disaster (landslide and flood): a Sicilian experience.

In this report, the authors provide a contribution of PMCT in assessing the cause of death due to natural disasters. Here, the PMCT findings of 43 subjects who died during both landslide and flood were described. The post-mortem imaging revealed, clearly, traumatic injuries and/or the presence of foreign material in airways allowing to assess the cause of death of each subject, together with external inspection and the collected circumstantial data. Particularly, the PMCT has been helpful for characterization and localization of the clogging substance in airways providing findings on bronchial branches involvement. Moreover, the investigation offered detailed data on skeletal injuries in all anatomic districts and put in evidence both the precise fracturing site and the characteristics of fracture stubs for each bone fracture. This report supports the recommendation of the virtual autopsy in a case with several victims, as in natural disasters, and its role as an alternative diagnostic investigation when the standard autopsy is not feasible.

Application of 3D printing in assessment and demonstration of stab injuries.

In stabbing related fatalities, the forensic pathologist has to assess the direction of wound track (thus, the direction of the stabbing) and the weapon's possible characteristics by examining the stab wound. The determination of these characteristics can be made only with a high level of uncertainty, and the precise direction of the stabbing is often difficult to assess if only soft tissues are injured. Previously reported techniques used for the assessment of these wound characteristics have substantial limitations. This manuscript presents a method using today's easily accessible three-dimensional (3D) printing technology for blade-wound comparison and wound track determination. Scanning and 3D printing of knives is a useful method to identify weapons and determine the precise stabbing direction in a stabbing incident without compromising the trace evidence or the autopsy results. Ballistic gel experiment, and dynamic stabbing test experiments prove the method can be applied in safety, without compromising the autopsy results. Identification of the exact knife is not possible with complete certainty but excluding certain knives will decrease the number of necessary DNA examinations, hence it can lower the burden on forensic genetic laboratories. The method addresses many of the shortcomings of previously used methods of probe insertion or post-mortem CT. Insertion of the printed knife into the wound gives a good visual demonstration of the stabbing direction, thus easing the forensic reconstruction of the stabbing incident. After combining the 3D printing with photogrammetry, the achieved 3D visualization is useful for courtroom demonstration and educational purposes.