Concealed Homicides-A Postmortem Study and Review.

ABSTRACT: A study was undertaken at Forensic Science SA, Adelaide, South Australia, of all cases of homicide (January 2003-December 2022) where the victims' bodies had been concealed. Three hundred twenty-six homicides were identified, which included 27 cases where bodies had been deliberately hidden (8%) (age range, 2-82 years; ave, 34.9 years; M:F = 1.5:1). Deaths were due to blunt force trauma (n = 11), sharp force trauma (n = 4), asphyxia (n = 4), gunshot wound (n = 2), and a combination of drowning and asphyxia (n = 1). In 5 cases, the cause of death was not determinable. The methods of concealment (which were sometimes overlapping) included the following: dumping at a hidden/isolated location (n = 8), burial (n = 7), dismembering (n = 3), incinerating (n = 3), hiding in a wheeled garbage bin (n = 2), disposing in garbage resulting in the remains being located at waste disposal facilities (n = 2), hiding in a shed (n = 1), under a concrete floor (n = 1), in a suitcase (n = 1), in a river (n = 1), in a mine shaft (n = 1), and in a septic tank (n = 1). Although it has been asserted that concealed homicides are rarely encountered in forensic practice, the current study has demonstrated that the bodies in at least 8% of victims of homicide in South Australia have undergone some form of concealment.

A comparative assessment of time-consuming and laborious diatom analysis：Brief experimentation with suggestion of automatic identification.

Diatom testing is considered a useful method for providing supportive evidence for the diagnosis of drowning in forensic pathology. However, various factors remain controversial for recognizing diatoms, such as being time-consuming and laborious and influencing the consistency of the results. Given the absence of precise and well-defined studies on this subject, this study aimed to determine the relationship between the ability to identify diatoms and researchers with different technical backgrounds. A total of 55 samples from 18 cases, including water, lungs, liver, and kidneys, were treated using the microwave digestion-vacuum filtration-automated scanning electron microscopy (MD-VF-Auto SEM), which was used to compare diatom analyses among three groups of well-trained forensic pathologists (FPs), trained junior employees (JEs), and new trainees (TEs). In addition to achieving similar accuracy of positive findings from drowning cases, counting efficiency was evaluated based on taxonomy records and counting time after viewing more than 5500 diatom images. In contrast to the higher counting efficiency of the JE group than that of the TE group, we observed a statistically significant difference (p < 0.05) in the diatom classification between these two groups. Based on our experiments, an efficient analysis for automatically identifying and classifying diatoms is urgently required.

Enhancing Water Safety: Exploring Recent Technological Approaches for Drowning Detection.

Drowning poses a significant threat, resulting in unexpected injuries and fatalities. To promote water sports activities, it is crucial to develop surveillance systems that enhance safety around pools and waterways. This paper presents an overview of recent advancements in drowning detection, with a specific focus on image processing and sensor-based methods. Furthermore, the potential of artificial intelligence (AI), machine learning algorithms (MLAs), and robotics technology in this field is explored. The review examines the technological challenges, benefits, and drawbacks associated with these approaches. The findings reveal that image processing and sensor-based technologies are the most effective approaches for drowning detection systems. However, the image-processing approach requires substantial resources and sophisticated MLAs, making it costly and complex to implement. Conversely, sensor-based approaches offer practical, cost-effective, and widely applicable solutions for drowning detection. These approaches involve data transmission from the swimmer's condition to the processing unit through sensing technology, utilising both wired and wireless communication channels. This paper explores the recent developments in drowning detection systems while considering costs, complexity, and practicality in selecting and implementing such systems. The assessment of various technological approaches contributes to ongoing efforts aimed at improving water safety and reducing the risks associated with drowning incidents.

Bone and Tooth: Substrates for determining Drowning: A new diagnostic procedure in forensic medicine Practice?

INTRODUCTION: Diatom tests are rarely used during autopsy to confirm drowning as the cause of death (COD) because of limitations of the current literature involving these techniques. Instead, experts rely on physical examination by the pathologist. Due to interpretive concerns regarding Diatom tests, they are often insufficient in establishing a diagnosis, but offer the potential to be an extremely useful diagnostic tool with further understanding. The aim of study is to optimize "Diatom Tests" for use in forensic medicine in Bosnia and Herzegovina. METHODS: A randomized prospective experimental study was conducted, using albino Wistar rat models (Rattus norvegicus), at the Veterinary Facility, University of Sarajevo. Thirty-two adult albino rats, were used and distributed into groups as follows: Group A (6 deceased rats with COD other than drowning, but due to mechanical asphyxia, which were then submerged for 1 h after death); Group B (6 deceased rats with COD other than drowning, but due to mechanical asphyxia, which were then submerged for 72 h after death); Group C (6 rats that were immediately autopsied after drowning, with COD determined as drowning); Group D (6 rats that underwent a 48-hour postmortem period after drowning); Group E (COD: drowning, post-mortem 72hrs after death, remained submerged in water until PM). Live algological material was collected for the research of the systematics of algae from the Bosna river, Sarajevo, and transported to the University of Sarajevo (Department of Biology, Faculty of Science). Periphyllon, epiphyllon and epipelon were used to collect phytobenthos. The material was fixed with 4% formalin solution. Laboratory processing of diatoms was performed using the methods described by Hustedt (16). In the process of obtaining pure diatom valves, part of the material is digested with potassium permanganate (KMnO4), sulfuric acid (H2SO4), and oxalic acid (C2H2O4). In the next step, the cleaned diatom valves were mounted in Canadian balsam. A light microscope under 1000x magnification (Best Scope 2020) was used to evaluate and analyze the species. The identification of diatoms was performed using the reference of Cantonati et al (17). The nomenclature of diatom species was performed according to Guiry & Guiry's worldwide electronic internet database. RESULTS: No diatoms were found in Groups A and B. However, Navicula sp. and Sellaphora sp. cf., were discovered during bone analysis of Group C where rats were immediately autopsied after drowning. Hantzschia amphioxus taxon was present in Group D, which underwent a 48-hour postmortem period after drowning and before samples were taken. In Groups C and D, where drowning was the COD, Diatoma vulgaris i Pinnularia major, Achnanthidium minutissimum i Melosira varians were present in the tooth samples. CONCLUSION: Optimization of the "Diatom Test" method could potentially lead to its future use as a routine method within experimental settings. This experimental study is a starting point that guides forenscic medicine pracitioners towards the optimization of tests and sampling in cases of unexplained etiology, where preserved soft tissue structures is not available. In these cases, teeth and bones serve as accessible materials for diagnosing COD, alongside standardized nonspecific findings in the absence of organs for micro- and macroanalysis.

Detection of diatoms in a case of mud aspiration at a coastal area.

The source of diatoms detected in non-drowned bodies have been attributed to postmortem invasion, contamination during autopsy or diatom testing, or "natural load." However, sand aspiration has not been reported as a source. Herein, we report an autopsy case in which diatoms were detected in a non-drowned human who had aspirated mud. A man in his 60 s was found dead at a harbor park in Japan. His whole body was covered with sand, including his face. A situational investigation suggested that he may have entered the sea. Autopsy revealed intratracheal mud, with no obvious findings indicating drowning, suggesting that he died from mud aspiration probably due to hypothermia or non-lethal ethanol intoxication. In the diatom test, 10-100 diatoms/g were detected in bilateral lung samples, which were similar to those found in the intraoral and intratracheal mud and the sand samples from around the discovery site and not similar to those found in the seawater samples. The diatoms in the stomach content exhibited an intermediate trend between those found in the sand and seawater. Therefore, careful qualitative and quantitative analyses are required to differentiate between true drowning and false-positives in non-drowning cases to determine the cause of death.

Automatic detection and identification of diatoms in complex background for suspected drowning cases through object detection models.

The diagnosis of drowning is one of the most difficult tasks in forensic medicine. The diatom test is a complementary analysis method that may help the forensic pathologist in the diagnosis of drowning and the localization of the drowning site. This test consists in detecting or identifying diatoms, unicellular algae, in tissue and water samples. In order to observe diatoms under light microscopy, those samples may be digested by enzymes such as proteinase K. However, this digestion method may leave high amounts of debris, leading thus to a difficult detection and identification of diatoms. To the best of our knowledge, no model is proved to detect and identify accurately diatom species observed in highly complex backgrounds under light microscopy. Therefore, a novel method of model development for diatom detection and identification in a forensic context, based on sequential transfer learning of object detection models, is proposed in this article. The best resulting models are able to detect and identify up to 50 species of forensically relevant diatoms with an average precision and an average recall ranging from 0.7 to 1 depending on the concerned species. The models were developed by sequential transfer learning and globally outperformed those developed by traditional transfer learning. The best model of diatom species identification is expected to be used in routine at the Medicolegal Institute of Paris.

The role of paranasal sinus fluid in determining drowning as the cause of death: A systematic review and meta-analysis.

Drowning is a significant global cause of unintentional injury fatalities, and accurate forensic diagnosis of drowning remains a challenge due to the nonspecific nature of post-mortem findings obtained through classical autopsy methods. Our manuscript addresses this issue by focusing on the emerging use of paranasal sinus fluid as a valuable tool in determining the cause of death, specifically in distinguishing drowning from non-drowning cases. The study provided a comprehensive summary of available evidence from observational studies that compared findings in the paranasal sinuses between drowning and non-drowning victims, analyzing parameters such as the presence of fluid, fluid volume, and density. The study encompassed a total of 14 selected studies involving 1044 subjects and utilized rigorous risk of bias assessment and data synthesis techniques. The meta-analysis demonstrated a strong association between the presence of fluid in the paranasal sinuses and drowning (OR = 17.1; 95% CI 7.2 to 40.5; p < 0.001). In addition, drowning victims had a significantly greater volume of fluid (SMD = 0.8; 95% CI 0.5 to 1.2; p < 0.001) and lower fluid density (SMD = -1.4; 95% -2.5 to -0.4; p = 0.008) compared to non-drowning cases. The results support the utility of paranasal sinus fluid analysis as a valuable diagnostic method in cases where drowning is suspected but cannot be definitively confirmed through traditional approaches.

Influence of the toxicological status on the diagnosis of fatal drowning.

Drowning is the leading cause of death by accident of everyday life in people under 25 years of age. Xenobiotics are frequently involved in drowning cases but their influence on the diagnosis of fatal drowning has not been studied so far. This preliminary study aimed to assess the influence of an alcohol and/or a drug intoxication on the autopsy signs of drowning, and on the results of diatom analyses in drowning deaths. Twenty-eight autopsy cases of drowning including 19 freshwater drownings, 6 seawater drownings, and 3 brackish water drownings were prospectively included. Toxicological and diatom tests were performed in each case. The influence of alcohol and other xenobiotics on drowning signs and diatom analyses was assessed separately then in combination through a global toxicological participation score (GTPS). Diatom analyses showed positive results in lung tissue in every case. No significant association was found between the degree of intoxication and the diatom concentration in the organs, even after considering freshwater drowning cases only. The vast majority of the traditional autopsy signs of drowning were not significantly affected by the individual toxicological status either, with the exception of lung weight which tended to raise in case of intoxication, probably due to the pulmonary edema and congestion increase. Further research on larger autopsy samples is needed to confirm the results of this exploratory study.

Colonization of diatoms in and on porcine bone substrate and considerations of diatom ecology for forensic science.

The presence of diatom algae in bone marrow has been used as forensic evidence of drowning for several decades; however, these studies are based on known or suspected recent drowning events. This study addresses the potential for diatoms to enter the bone marrow of skeletal remains, that is, de-fleshed long bones post-mortem. In laboratory and field experiments, bones were either inflicted with two access points by a cut and acid pitting or left intact. The bones were submerged in water for at least 1 week and up to 3 months. Samples of the bone surface and marrow were inspected for diatoms. The analysis considered the time required for diatoms to enter marrow and whether genus characteristics like size or mobility affect entry. The presence of an access point influenced diatom entry in that bones without an introduced access point had zero to one diatom present in the marrow, whereas a bone with an access point had >150 diatoms present in the marrow. The results of both laboratory and field phases suggest that diatoms will reliably colonize bone in as quickly as 1 week, establishing and maintaining communities for at least 3 months. However, the bone surface assemblages differ from the source community. Bone marrow displayed even more restrictive access to diatom colonization, resulting in communities dominated by small raphid diatoms. Based on these findings, we suggest some caveats on the use of diatoms as trace evidence in forensic science with recommendations for future avenues of research.

A method for bone marrow extraction of diatoms for forensic science applications.

Diatoms show potential as trace evidence indicators, particularly as evidence of drowning. Often, the diatom test to diagnose drowning is done on soft tissue or bone marrow from a recently deceased individual. This method presented here combines elements from previous forensic literature and methods of diatom isolation in phycology to extract diatoms from bone marrow of skeletal remains for forensic use. This diatom extraction method is time-efficient, minimizes contamination risk, and produces samples of intact diatoms. This method is designed to complete sample preparation within 24 h, sampling the bone for diatoms internally and externally. This method was developed using porcine long bones submerged in water with live diatoms for up to 3 months. Three marrow samples were extracted from each bone so the method was developed using 102 marrow samples. Additionally, 132 surficial bone and environmental samples were collected and prepared during method development. To briefly summarize the method, the bone joints were cut off with an angle grinder in a biosafety hood to expose the marrow, which was removed from the hip, knee, and shaft as separate samples. The marrow was digested with nitric acid at 400°C in glass beakers before being centrifuged with DI water, plated onto microscope slides, and observed with a compound microscope. Observation found good preservation of unbroken diatom cell walls throughout the process. This method can be used to prepare diatoms as forensic trace evidence.

Black box of diving accidents: Contribution of forensic underwater experts to three fatal cases.

Diving is a popular activity, largely practiced worldwide. Diving fatalities are not rare events, with drowning being the most common cause of death, followed by cardiac-related natural causes, immersion pulmonary edema and arterial gas embolism. In such cases, positive signs of drowning are not specific, depending also on the time of submersion of corpses. Moreover, drowning can be the terminal event. Over the years, measures to perform appropriate post-mortem examination in cases of diving fatalities were suggested, including the execution of post-mortem CT-scan, the use of a decompression chamber and the adoption of specific autoptic techniques. Although a multidisciplinary approach in forensic investigations concerning diving fatalities is discussed, poor cases focus on how the analysis of diving computer records and equipment can contribute to determining the cause of death. The present study shows how the cooperation between a forensic underwater expert and a forensic pathologist played a crucial role in interpreting radiological findings, guiding the autopsy and confirming/denying circumstantial data emerging from the investigations. Technical analysis of dive computer records and diving equipment is a fundamental step in the definition of the cause of death in diving fatalities. All diving computer data, not only those related to maximum depth and ascent's profile, should be considered in detail, and the immersion graph carefully studied by both the forensic pathologist and the forensic underwater experts. The diving technical data can often play a crucial role in explaining any legal issue related to the circumstances of death, possibly leading the prosecutor to further investigation.

Applicable Forensic Biomarker for Drowning Diagnosis: Extracellular Signal-Regulated Kinase 2 (ERK2).

Drowning is a common cause of accidental death worldwide, and it continues to be a serious public health problem. However, diagnosing drowning is a challenging task in forensic investigation because it is difficult to prove actual drowning and other submerged deaths with the autopsy techniques that are currently in use. Here, we show biomarkers that may be helpful for the diagnosis of drowning. We divided the experimental animals into four groups (drowning, postmortem submersion, hypoxia, and control) to evaluate the expression patterns of extracellular signal-regulated kinase 1/2 (ERK1/2). On gene expression analysis, only ERK2 was found to be significantly increased in the drowning groups compared to the other cases. In the immunoblot analysis, phosphorylated ERK2 (p-ERK2) was found to be upregulated in the drowning groups. Immunohistochemical staining also showed that p-ERK in alveolar cells revealed a granular pattern in the drowning groups. However, the expression pattern of ERK2 over time after drowning differed between the freshwater and seawater drowning groups. Taken together, these results indicate that ERK2 may be useful for distinguishing between drowning and postmortem submersion if the postmortem interval (PMI) of drowning is short. Conversely, if the PMI is long from the time that death occurs until the discovery of dead bodies, it is possibly more helpful for identifying between freshwater and seawater drowning.

The possibilities and limitations of comparative diatomaceous analysis for confirming or excluding the site of an incident - Case studies.

Diatoms (Bacillariophyta) are unicellular photosynthetic organisms commonly occurring in aquatic habitats on Earth. Their autecology makes them almost perfect indicators of environmental conditions and so have high potential for use in forensics. Both eurytopic and stenotopic species are important in site identification: eurytopic forms due to their abundance, and stenotopic forms due to their narrow range of tolerance to environmental conditions. Their presence can hence provide a clear insight into an ecosystem and its microhabitats. The diatoms are useful as significant indicator in diagnosing of drowning. However, to definitively link a corpse with the place where it was found and to indicate whether this was also the crime scene, it is essential that any comparative diatomaceous analyses are performed correctly. The following study presents selected cases in which a comparative diatomaceous analysis was performed. In all cases, the biological samples secured during the autopsy were compared with environmental samples collected from the site of the cadaver disclosure. Our findings show both the possibilities and limitations of using this method in forensics. These forensic investigations need close collaboration between coroners and diatomology experts. It is crucially important to reveal whether the place of corpse finding is the same as the place of drowning.

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.

DiatomNet v1.0: A novel approach for automatic diatom testing for drowning diagnosis in forensically biomedical application.

BACKGROUND AND OBJECTIVE: Diatom testing is supportive for drowning diagnosis in forensic medicine. However, it is very time-consuming and labor-intensive for technicians to identify microscopically a handful of diatoms in sample smears, especially under complex observable backgrounds. Recently, we successfully developed a software, named DiatomNet v1.0 intended to automatically identify diatom frustules in a whole slide under a clear background. Here, we introduced this new software and performed a validation study to elucidate how DiatomNet v1.0 improved its performance with the influence of visible impurities. METHODS: DiatomNet v1.0 has an intuitive, user-friendly and easy-to-learn graphical user interface (GUI) built in the Drupal and its core architecture for slide analysis including a convolutional neural network (CNN) is written in Python language. The build-in CNN model was evaluated for diatom identification under very complex observable backgrounds with mixtures of common impurities, including carbon pigments and sand sediments. Compared to the original model, the enhanced model following optimization with limited new datasets was evaluated systematically by independent testing and random control trials (RCTs). RESULTS: In independent testing, the original DiatomNet v1.0 was moderately affected, especially when higher densities of impurities existed, and achieved a low recall of 0.817 and F1 score of 0.858 but good precision of 0.905. Following transfer learning with limited new datasets, the enhanced version had better results, with recall and F1 score values of 0.968. A comparative study on real slides showed that the upgraded DiatomNet v1.0 obtained F1 scores of 0.86 and 0.84 for carbon pigment and sand sediment, respectively, slightly worse than manual identification (carbon pigment: 0.91; sand sediment: 0.86), but much less time was needed. CONCLUSIONS: The study verified that forensic diatom testing with aid of DiatomNet v1.0 is much more efficient than traditionally manual identification even under complex observable backgrounds. In terms of forensic diatom testing, we proposed a suggested standard on build-in model optimization and evaluation to strengthen the software's generalization in potentially complex conditions.

Virtual reality lifeguarding scenarios as a potential training solution for pool lifeguards.

BACKGROUND: Ensuring that pool lifeguards develop the skills necessary to detect drowning victims is challenging given that these situations are relatively rare, unpredictable and are difficult to simulate accurately and safely. Virtual reality potentially provides a safe and ecologically valid approach to training since it offers a near-to-real visual experience, together with the opportunity to practice task-related skills and receive feedback. As a prelude to the development of a training intervention, the aim of this research was to establish the construct validity of virtual reality drowning detection tasks. METHOD: Using a repeated measures design, a total of 38 qualified lifeguards and 33 non-lifeguards completed 13 min and 23 min simulated drowning detection tasks that were intended to reflect different levels of sustained attention. During the simulated tasks, participants were asked to monitor a virtual pool and identify any drowning targets with accuracy, response latency, and dwell time recorded. RESULTS: During the simulated scenarios, pool lifeguards detected drowning targets more frequently and spent less time than non-lifeguards fixating on the drowning target prior to the drowning onset. No significant differences in response latency were evident between lifeguards and non-lifeguards nor for first fixations on the drowning target. CONCLUSION: The results provide support for the construct validity of virtual reality lifeguarding scenarios, thereby providing the basis for their development and introduction as a potential training approach for developing and maintaining performance in lifeguarding and drowning detection. APPLICATION: This research provides support for the construct validity of virtual reality simulations as a potential training tool, enabling improvements in the fidelity of training solutions to improve pool lifeguard competency in drowning detection.

Objective evaluation of chest findings in infants by postmortem computed tomography.

PURPOSE: The purpose of this study was to review the findings of computed tomography (CT) performed early postmortem on infants and to clarify the postmortem CT lung findings that occur in the absence of abnormal histopathological findings. MATERIALS AND METHODS: From July 2016 to March 2022, 72 infants were autopsied with postmortem CT (41 boys 31 girls, aged 0-36 (mean 8.2) months). Autopsy and postmortem CT lung findings were compared with the causes of death identified by the autopsies, namely sudden infant death syndrome (n = 37), acute circulatory system disease (18), drowning (7), asphyxia (5), and dehydration/undernutrition (5). RESULTS: The %aerated lung volume (-700 HU or less) ranged from 0 % to 33 % (mean 1.5 %, median 0 %), being <1 % in 61 cases (84.7 %) and >3 % in 3/5 (60 %) of the dehydration/undernutrition group. The dehydration/undernutrition group showed significant preservation of lung field air content compared with the other causes of death groups (p < 0.05). Receiver characteristic curve analysis showed a cut off value of 0.8 % and area under the curve of 0.88806. The drowning group had significantly greater pleural cavity fluid retention than the other causes of death groups (p < 0.05). No correlation was found between postmortem interval and pleural cavity fluid retention. However, resuscitation time and pleural cavity fluid retention were correlated. CONCLUSION: Evaluation of CT values on postmortem lung fields of infants usually reveals a marked decrease in air content. When air content exceeds 0.8% on infant postmortem CT, dehydration/undernutrition should be considered in the differential diagnosis.

Relevance of diatom testing on closed organs of a drowned cadaver who died after receiving treatment for 10 days: A case report.

A male in his late adolescence fell into the sea and was found 50 min later with cardiopulmonary arrest. He was revived approximately 260 min after he drowned. Although he received several treatments, including venoarterial extracorporeal membrane oxygenation and continuous hemodiafiltration, he was clinically diagnosed with brain death. He died 10 days after the accident. The autopsy did not reveal any unremarkable findings other than those associated with post-resuscitation changes and medical treatment. The diatom test revealed 47.9, 311.6, and 577.5 diatom particles per gram from water, left lung, and right lung samples, respectively. No diatoms were detected in a 10 g liver sample, and 1 diatom was detected in each of approximately 12 g of bilateral kidney samples, which was different from the abundant species in the lung samples. The diatom test of the closed organs could be considered false negative for confirming drowning death since diatoms can also be detected in non-drowned cadavers on dry land. This suggests that diatoms might not reach the closed organs via circulation and that the diatom test of closed organ samples might no longer be necessary to confirm drowning deaths.

Conventional diatom testing using strong acid: (II) Number and types of diatoms detected in closed organs and lungs of 80 autopsy cases using only new Kjeldahl flasks.

The number of diatoms detected in the kidneys and liver varies considerably when comparing various reports, but the reason remains unclear. We previously showed that the reuse of Kjeldahl flasks is susceptible to generating false positives; false-positive results were observed in 17 of 60 tested flasks, and a maximum of 290 diatoms were detected. Furthermore, these data suggested that the number of diatoms in kidney and liver tissue may be much lower than previously thought. Therefore, only new Kjeldahl flasks were used to perform diatom tests on 80 autopsy cases (drowning and non-drowning victims) in this study. When combined with the 20 cases in a previous study, a total of 100 cases were analyzed. Four grams of lung, 10-30 g each of kidney and liver, 10 mL of blood, and 50-100 mL of water (discovery site) were examined. A large number of diatoms (n = 400) were found in organs other than the lungs in only 1 of 56 cases of suspected drowning (excluding cases of suspected drowning in baths). Together with the previous 20 cases, this single case represented only 1 of 76 cases (1.3 %). In closed organs and blood samples, 3 diatoms were found in 2 of 56 victims (3.6 %), and 1 or 2 diatoms were found in 8 victims (14 %). However, 5 diatoms were found in 1 of 10 bathtub drowning victims and 12 non-drowning victims (4.5 %), and 1 or 2 diatoms were found in 6 victims (27 %). Moreover, 1 or 2 diatoms were found in negative control flasks in 3 of 80 victims (3.8 %). The results showed that distinguishing false-positive results is difficult when a small number of diatoms are found in the kidneys and liver. Thus, the presence of diatoms in closed organs and blood seems to be unreliable as evidence of death by drowning, at least in the water environments in our region (freshwater areas: 23-26,000 diatoms/mL, median 200 diatoms; brackish water areas: 26-1200 diatoms/mL, median 210 diatoms; seawater area: 2-1000 diatoms/mL, median 24 diatoms). These results also reconfirmed that the reuse of flasks is the most important cause of false positives. Conversely, the presence of a large number of diatoms in lung samples (1-850,000 diatoms/g lung tissue; median (right lung): 440 diatoms, (left lung): 320 diatoms) is very informative and is an effective diagnostic aid in many cases.

Forensic Diagnosis of Freshwater or Saltwater Drowning Using the Marker Aquaporin 5: An Immunohistochemical Study.

Background and Objectives: Aquaporins are a family of water channel proteins. In this study, the renal and intrapulmonary expression of aquaporin-5 (AQP5) was examined in forensic autopsy cases to evaluate it as a drowning marker and to differentiate between freshwater drowning and saltwater drowning. Materials and Methods: Cases were classified into three groups: freshwater drowning (FWD), saltwater drowning (SWD), and controls (CTR). Samples were obtained from forensic autopsies at less than 72 h postmortem (15 FWD cases, 15 SWD cases, and 17 other cases) and were subjected to histological and immunohistochemical investigations. Results: In FWD group, intrapulmonary AQP5 expression was significantly suppressed compared with SWD and CTR; there was no significant difference in AQP5 expression among the other two groups. The same differences in expression were also observed in the kidney. Conclusions: These observations suggest that AQP5 expression in alveolar cells was suppressed by hypotonic water to prevent hemodilution. Moreover, it is possible to hypothesize that in the kidney, with the appearance of hypo-osmotic plasma, AQP5 is hypo-expressed, as a vital reaction, to regulate the renal reabsorption of water. In conclusion, the analysis of renal and intrapulmonary AQP5 expression would be forensically useful for differentiation between FWD and SWD, or between FWD and death due to other causes.