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During the coronavirus disease 2019 (COVID-19) pandemic, autopsies have provided valuable insights into the pathogenesis of COVID-19. The precise effect of this pandemic on autopsy procedures in Japan, especially in instances unrelated to COVID-19, has not yet been established. Therefore, we conducted a questionnaire survey from December 2020 to January 2021 regarding the status of pathological autopsy practices in Japan during the first year of the COVID-19 pandemic. The questionnaire was sent to 678 medical facilities with pathologists, of which 227 responded. In cases where a confirmed diagnosis of COVID-19 was not made at the time of autopsy, many facilities counted them as suspected COVID-19 cases if pneumonia was suspected clinically. At around half of the sites, autopsies were prohibited for suspected COVID-19 cases. In addition, the number of autopsies of non-COVID-19 cases during the pandemic period was also investigated, and a significant decrease was observed compared with the incidence in the pre-pandemic period. The COVID-19 pandemic has affected not only the autopsies of COVID-19 cases but also the entire practice of pathological autopsies. It is necessary to establish a system that supports the implementation of pathological autopsy practices during the pandemic of an emerging infectious disease.

Forensic entomology (FE) involves the collection and analysis of necrophagous insects and arthropods for postmortem interval estimation based on their growth and succession. In Japan, research on FE is limited, and the predominant species of necrophagous insects and their distribution have not been clarified. The present study aimed to clarify the actual situation of insects, targeting Diptera collected from human cadavers, in Chiba Prefecture. We targeted the cases for which specimens could be collected from forensic autopsies conducted at the Legal Medicine Department of Chiba University Graduate School of Medicine or from human bodies handled by the Chiba Police in 2019. We specifically chose cases from which adult insects could be bred. Fifty cases were applicable, and 47 cases were successful in rearing adult flies. Sixteen species of Diptera were identified: six species of Calliphoridae, four species of Sarcophagidae, and a few species of Fanniidae, Muscidae, Phoridae, Piophilidae, and Stratiomyidae. The most frequently observed species were Lucilia sericata (20 cases) and Chrysomya pinguis (18 cases). For the first time, globally, we recorded the presence of Fannia prisca in a human cadaver. In conclusion, this is the first report to reveal the presence of carrion flies in human death cases in Chiba Prefecture, Japan. Research in FE is important in the context of the Japanese natural and social environment since this can aid forensic investigations conducted by authorities.

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Supplementary Figures S1-S13

Estimation of age at death is important in forensic investigations of unknown remains. There have been several reports on applying the degree of osteophyte formation—an age-related change in the vertebral body—for age estimation; however, this method is not yet established. This study investigated a method for age estimation of modern Japanese individuals using osteophytes measured on CT images. The sample included 250 cadavers (125 males) aged 20–95 years. The degree of osteophyte formation was evaluated as score O (0–5 points), and the degree of fusion of the osteophytes between the upper and lower vertebrae was evaluated as score B (0–2 points). Age estimation equations were developed using regression analyses with seven variables, determined by scores O and B, and the equation with the smallest standard error of estimate (SEE) was obtained when the number of vertebrae with score O ≥ 2 was used as the explanatory variable. Age estimation with SEE of about 10 years was possible even when partial vertebrae with a high degree of osteophyte formation were used, showing its potential for practical application. The cutoff value for age estimation was established using the receiver operating characteristic curve analysis, wherein good results were obtained for all variables (area under the curve ≥ 0.8). The combination of the estimation equation and the cutoff value can narrow the range of age estimates.

Image acquisition of dead bodies, particularly using postmortem computed tomography (PMCT), has become common in forensic investigations worldwide. Meanwhile, in countries such as Japan which have an extremely low rate of autopsy, PMCT is being increasingly used in the clinical field to certify the cause of death (COD) without performing an autopsy or toxicological tests, even in cases of unnatural death. Additionally, these PMCT images are predominantly interpreted by clinical personnel such as emergency physicians or clinicians who are not trained in PMCT interpretation and who work for the police, that is, the so-called police doctors. Many potential pitfalls associated with the use of PMCT have been previously described in textbooks and published papers, including the pitfalls of not performing a complete forensic pathology investigation, and the use of physicians without appropriate PMCT training to interpret PMCT and direct death investigation and certification. We describe five examples in which apparent misdiagnosis of COD based on PMCT misinterpretation was revealed by autopsy. Here are the five examples of errors: (1) Postmortem changes were misinterpreted as COD, (2) resuscitation effects were misinterpreted as COD, (3) COD was determined after an incomplete examination, (4) fatal findings caused by external origin were wrongly interpreted as 'of internal origin' based on PMCT, and (5) non-fatal findings on PMCT were wrongly interpreted as fatal. Interpretation of PMCT by appropriately trained physicians and an accompanying complete forensic investigation, including autopsy when indicated, is necessary to prevent significant errors in COD determination and related potential adverse medicolegal consequences.

Acupuncture is practiced as a complementary medicine worldwide. Although it is considered a safe practice, pneumothorax is one of its most common serious complications. However, there have been few reports of deaths due to pneumothorax after acupuncture treatment, especially focused on electroacupuncture. We report an autopsy case of a man in his 60s who went into cardiopulmonary arrest and died immediately after receiving electroacupuncture. Postmortem computed tomography (PMCT) showed bilateral pneumothoraces, as well as the presence of numerous gold threads embedded subcutaneously. An autopsy revealed two ecchymoses in the right thoracic cavity and a pinhole injury on the lower lobe of the right lung, suggesting that the needles had penetrated the lung. There were marked emphysematous changes in the lung, suggesting that rupture of bullae might also have contributed to bilateral pneumothoraces and fatal outcome. The acupuncture needles may have been drawn deeper into the body than at the time of insertion due to electrical pulses and muscle contraction, indicating the need for careful determination of treatment indications and technical safety measures, such as fail-safe mechanisms. This is the first case report of fatal bilateral pneumothoraces after electroacupuncture reported in the English literature. This case sheds light on the safety of electroacupuncture and the need for special care when administering it to patients with pulmonary disease who may be at a higher risk of pneumothorax. This is also the first report of three-dimensional reconstructed PMCT images showing the whole-body distribution of embedded gold acupuncture threads, which is unusual.

Ropinirole is an antiparkinsonian drug and has recently been suggested to be effective in amyotrophic lateral sclerosis. It is expected that ropinirole prescriptions will increase in the near future. However, the fatal concentration in blood is unclear at this time. Therefore, we report a fatal case involving ropinirole intoxication and discuss the fatal concentrations with reference to several autopsy cases involving ropinirole. Ropinirole was quantified in femoral vein blood, cardiac blood, and urine from five autopsy cases in which ropinirole was detected by drug screening in our laboratory. One is a ropinirole intoxication case (this report) and the others were non-intoxication cases. Their ropinirole concentrations were compared and discussed. The ropinirole concentration in this case was 100 ng/mL in femoral blood, 160 ng/mL in cardiac blood, and 1840 ng/mL in urine. The ropinirole concentrations in the four non-ropinirole poisoning cases were 7–35 ng/mL (mean: 24 ng/mL) in femoral blood, 13–100 ng/mL (mean: 60 ng/mL) in cardiac blood, and 140–1090 ng/mL (mean: 640 ng/mL) in urine. Cardiac/peripheral ratios were in the range of 1.6–2.1 (mean 1.8). There were no obvious signs of overdose, and the high cardiac/peripheral blood ratio suggested that postmortem redistribution may have occurred, but the peripheral blood ropinirole concentration (100 ng/mL) was obviously higher than that reported in the previous fatal case of ropinirole poisoning (64 ng/mL). Based on these results, the cause of death in this case was considered to be shock and fatal arrhythmia due to ropinirole poisoning. This case provides important data on postmortem blood and urinary levels of ropinirole poisoning.

BackgroundThe prolonged presence of infectious severe acute respiratory syndrome coronavirus (SARS-CoV-2) in deceased coronavirus disease 2019 (COVID-19) patients has been reported. However, infectious virus titers have not been determined. Such information is important for public health, death investigation, and handling corpses.AimThe aim of this study was to assess the level of SARS-CoV-2 infectivity in COVID-19 corpses.MethodsWe collected 11 nasopharyngeal swabs and 19 lung tissue specimens from 11 autopsy cases with COVID-19 in 2021. We then investigated the viral genomic copy number by real-time reverse transcription-polymerase chain reaction and infectious titers by cell culture and virus isolation.ResultsInfectious virus was present in 6 of 11 (55%) cases, 4 of 11 (36%) nasopharyngeal swabs, and 9 of 19 (47%) lung specimens. The virus titers ranged from 6.00E + 01 plaque-forming units (PFU)/mL to 2.09E + 06 PFU/g. In all cases in which an infectious virus was found, the time from death to discovery was within 1 day and the longest postmortem interval was 13 days.ConclusionCOVID-19 corpses may have high titers of infectious virus after a long postmortem interval (up to 13 days). Therefore, appropriate infection control measures must be taken when handling corpses.

To study the quantitative effect of ethanol on the diatom test for water and lung samples.In experiment 1, we tested 20 water samples taken from natural water areas. In experiments 1-1 and 1-2, each sample was digested with sodium hypochlorite (NaClO) solution (Purelox) and fuming nitric acid (HNOIn experiments 1-1, 1-2, 1-3, 1-4, and 2, the geometric means of the ratios derived from the two methods (with/without ethanol) were 0.70 (95 % confidence interval [CI]: 0.65-0.77, P 0.001), 0.83 (95 % CI: 0.73-0.93, P = 0.005), 3.00 (95 % CI: 2.31-3.91, P 0.001), 0.91 (95 % CI: 0.79-1.04, P = 0.164), and 3.06 (95 % CI: 2.28-4.41, P 0.001), respectively.Our experiments suggest that ethanol would be useless in diatom tests of water samples or in the conventional (HNO

Although it has been 2.5 years since the COVID-19 pandemic began, the transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a dead infected body remains unclear, and often, in Japan bereaved family members are not allowed to view in-person a loved one who has died from COVID-19. In this study, we analyzed the possibility of SARS-CoV-2 transmission from a dead body by using the hamster model. We also analyzed the effect of Angel-care––in which the pharynx, nostril, and rectum are plugged––and embalming on reducing transmissibility from dead bodies. We found that SARS-CoV-2 could be transmitted from the body of animals that died within a few days of infection; however, Angel-care and embalming were effective in preventing transmission from the dead body. These results suggest that protection from infection is essential when in contact with a SARS-CoV-2-infected dead body, and that sealing the cavities of a dead body is an important infection control step if embalming is not done.ImportanceWe found that SARS-CoV-2 could be transmitted from a dead body presumably via postmortem gases. However, we also found that postmortem care, such as plugging the pharynx, nostrils, and rectum, or embalming could prevent transmission from the dead body. These results indicate that protection from infection is essential when handling infected corpses, and that appropriate care of SARS-CoV-2-infected corpses is important.

In Japan, a new cause-of-death investigation system and related new laws were enacted in the mid-2010s. These laws provided for an autopsy system for non-criminal unnatural deaths and a medical accident investigation system outside the criminal justice process for health care-related deaths. We retrospectively explored changes in the number and characteristics of medico-legal autopsy cases of health care-related deaths in Chiba Prefecture, Japan, and examined trends over time during these reforms. We found that the percentage of forensic autopsies based on the Code of Criminal Procedure for health care-related deaths had decreased significantly. The number of autopsies of accidental and unintentional deaths in nursing homes, which are not covered by the newly established medical accident investigation system, has been increasing, reflecting the ageing of society. The trend toward decriminalisation of health care-related deaths was expected to contribute more to medical safety if the scope was expanded and a system for disclosure of autopsy information was established.

Oxime-type carbamate pesticides having an oxime moiety such as aldicarb, butocarboxim, methomyl, oxamyl, and thiofanox are widely used and have been detected in many fatal cases of accidental exposure or suicide. In forensic toxicology, the accurate determination of blood pesticide concentration is obligatory to prove death by oxime-type carbamate pesticide poisoning. However, the fatal pesticide concentration in blood at autopsy differs from that at the time of death. In this study, we found that oxime-type carbamate pesticides were decomposed by Hb in a temperature-dependent fashion. The mechanism underlying methomyl, aldicarb, oxamyl, and thiofanox decomposition involves the formation of adducts with the amino acids in Hb. With regard to butocarboxim, its decomposition involves the oxidation of the free form and the formation of adducts with the amino acids in Hb. The mass spectra obtained by liquid chromatography quadrupole time-of-flight mass spectrometry revealed that carbamylated amino acid adducts such as W

Ludwig's angina is characterized by inflammation of the sublingual and submandibular spaces and is mainly caused by odontogenic infection, which leads to cellulitis of the soft tissues of the floor of the mouth and the neck. This causes asphyxia due to elevation and posterior deviation of the tissues of the floor of the mouth. We report a fatal case of airway obstruction due to Ludwig's angina. A woman in her forties who had no physical complications, but had a mental illness, was undergoing outpatient dental treatment for caries in the first premolar of the left mandible. She was admitted to a psychiatric hospital because of insomnia caused by pain, where she developed cardiopulmonary arrest while sleeping and died 14 days after onset of the dental infection. Postmortem computed tomography (PMCT) prior to autopsy showed swelling of the soft tissues-from the floor of the mouth to the oropharyngeal cavity, the supraglottic larynx, and the prevertebral tissue. Autopsy revealed a markedly swollen face and neck, an elevated tongue, and a highly edematous epiglottis and laryngopharyngeal mucosa. There was also cellulitis and abscess of the facial, suprahyoid, and neck musculature, which suggested that the cause of death was asphyxiation due to airway obstruction. This was an alarming case, with mental illness leading to risk of severe odontogenic infection, and in which obesity and use of antipsychotic medication might have acted synergistically leading to airway obstruction. This is also a case of Ludwig's angina captured by PMCT, which has rarely been reported.

Understanding the actual conditions of methamphetamine (MA)-related death is important from the perspectives of criminal justice and public health. In this report, we review 104 cases of MA-related death handled by our departments between January 2014 and December 2020. Based on information from police and autopsy examinations, we classified the cases into the following categories: "accidental intoxication" ("MA only" and "multiple drugs or alcohol"), "fatal disease" ("definitively MA-related," "possibly MA-related," and "unlikely MA-related"), "accident," "suicide," "homicide," and "undetermined." The total number and annual trends for each category and their respective femoral blood concentrations were investigated. "Fatal disease" was the most common category (48 cases), followed by "suicide" (25 cases), "accidental intoxication" (14 cases), and "accident" (11 cases). "Definitively MA-related" in which MA may have played a role in their onset or exacerbation accounted for the majority of "fatal disease": 12 cases of heart disease, 4 cases of aortic dissection, 12 cases of cerebral hemorrhage, and 4 cases of subarachnoid hemorrhage. Cases classified as "definitively MA-related" died with lower femoral blood concentrations of MA compared with "MA only." Cases with "fatal disease" might have been misdiagnosed as "death by natural causes" if a proper autopsy and toxicology examinations were not performed. In death investigations, it is necessary to keep in mind that there are some MA-related deaths, and efforts should be made to increase awareness about the risk of death in using this drug.

A man and a woman were found dead in the same car with a burned coal briquette. The cause of death of the woman was assigned to acute carbon monoxide (CO) poisoning without difficulty based on typical findings associated with this condition, including elevation of carboxyhaemoglobin (COHb). However, the man had an unremarkable elevation of COHb and a higher rectal temperature compared to that of the woman. Postmortem computed tomography (PMCT) revealed ambiguous low-density areas in the bilateral globi pallidi. Further analysis by postmortem magnetic resonance (PMMR) imaging showed these lesions more clearly; the lesions appeared as marked high signal intensity areas on both the T2-weighted images and the fluid-attenuated inversion recovery sequences. A subsequent autopsy revealed signs of pneumonia, dehydration, starvation, and hypothermia, suggesting that the man died from prolonged CO poisoning. Both globi pallidi contained grossly ambiguous lesions, and a detailed neuropathologic investigation revealed these lesions to be coagulative necrotic areas; this finding was compatible with a diagnosis of prolonged CO poisoning. This case report shows that postmortem imaging, especially PMMR, is useful for detecting necrotic lesions associated with prolonged CO poisoning. This report further exemplifies the utility of PMMR for detecting brain lesions, which may be difficult to detect by macroscopic analysis.

To statistically clarify the prevalence and risk factors of infections in forensic autopsy cases in Chiba Prefecture, Japan. The aim was to improve preventive measures against infection in forensic autopsies.We retrospectively investigated the positive detection rates of five infections (hepatitis B, HBV; hepatitis C, HCV; human immunodeficiency virus, HIV; human T-lymphotropic virus, HTLV; Treponema pallidum, TP) using 1491 samples obtained in forensic autopsy at our facility from 2014 to 2018. In addition, risk factors related to infection such as methamphetamine and tattoos were analyzed. Pearson's chi-square test was used for statistical analysis, and the difference was judged to be significant at p 0.05.Among our samples, 9.0% of cadavers tested positive for infection, and the prevalence rates for HBV, HCV, HIV, HTLV, and TP were 1.0%, 6.7%, 0.3%, 0.7%, and 1.1% respectively. Statistically, cadavers linked to information about methamphetamine use had a 7.2 times higher rate of infection, and those with tattoos had a 5.6 times higher rate of infection, with HCV being the predominant cause.To limit the risk of infection among autopsy workers, cadavers and samples should be handled on the presupposition that the bodies are at risk of infections. It is also important to obtain as much information as possible about the medical history and potential illegal drug use to help assess the risk of infection in a patient during forensic autopsy. We propose that all autopsy cases should be screened for infections whenever possible.

Purpose Lisdexamfetamine (LDX), which is used for the treatment of attention-deficit/hyperactivity disorder and narcolepsy, is composed of l-lysine attached to dextroamphetamine (d-amphetamine). In this article, we report a forensic autopsy case in which prescription drugs were unknown at autopsy. While amphetamine was detected, methamphetamine could not be detected by liquid chromatography–tandem mass spectrometry (LC–MS/MS) in any of samples collected. Thus, we aimed to quantify LDX concentrations in autopsy samples and to prove that the amphetamine detected in this case was due to metabolized LDX. Methods Femoral vein blood, cardiac whole blood, urine, and gastric content samples were taken at autopsy for toxicological analysis. Qualitative and quantitative analyses were performed using LC–MS/MS. In addition, optical isomer separation for the amphetamine detected was conducted. The stability of LDX in whole blood and urine was also examined at three different temperatures. Results The concentrations of LDX were d-amphetamine by optical isomer separation. The d-amphetamine detected was considered to be derived from LDX. Stability experiments revealed that LDX in whole blood decreased at ambient temperature. Conclusions The results in the present case report may be useful in interpreting whether or not the amphetamine detected in a cadaver is a metabolite of LDX.

Methidathion [3-(dimethoxyphosphinothioylsulfanylmethyl)-5-methoxy-1,3,4-thiadiazol-2-one; hereinafter DMTP], one of the most widely used organophosphorus pesticides, has been detected in some clinical cases of accidental exposure and suicide in Japan. It has been reported that DMTP concentration is decreased in blood. In this study, it is difficult to recover DMTP in the free form because DMTP is bound to human serum albumin (HSA). We detected DMTP adducts in HSA by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q/TOF-MS). The mass spectra showed that DMTP was preferably bound to the lysine (K), tyrosine (Y), and cysteinylproline (CP) residues of HSA. The concentrations of K-adduct, DMTP-Y-adduct and DMTP-CP-adduct were increased in vitro in a dose-dependent fashion when DMTP concentration was lower than the lethal dose. Furthermore, the DMTP-Y-adduct and DMTP-CP-adduct were also detected in post-mortem blood of an autopsied subject who died by intentional DMTP ingestion. The results suggested that the DMTP-Y-adduct and DMTP-CP-adduct could be used as a biomarker of DMTP poisoning, and the decrease concentration of DMTP in blood after death could be determined on the basis of the concentration of the DMTP-CP-adduct in blood.

A man in his seventies who lived alone was found dead in his home. Postmortem computed tomography (CT) performed prior to autopsy showed right-sided tension pneumothorax. Autopsy revealed an active pulmonary tuberculosis (TB) lesion. Macroscopic and histopathological findings showed pleural infiltration by TB lesions, suggesting that tension pneumothorax developed in association with TB infection. Routine postmortem CT performed prior to autopsy is useful in screening for TB because the presence of TB lesions can be confirmed from characteristic pulmonary findings. However, it may be difficult to identify tuberculous pulmonary lesions on CT if pneumothorax occurs and the lung collapses completely as in this case. Thus, forensic pathologists and radiologists should be cognizant of this rare complication of TB.

The autopsy rate in Japan is lower than that in other countries, and most death investigations have historically been conducted by police officers through external inspection. Although medicolegal autopsy was not performed during the samurai administration, the European death investigation system was adopted in the second half of the 19th century and judicial autopsy began in universities’ forensic medicine departments. After World War II, the medical examiner system was introduced under US influence, but it was only adopted in certain areas. Further reforms were introduced in the 21st century—in 2012, two laws relating to death investigation were enacted: The Act on Promotion of Death Investigation (Promotion Act), which provided foundational principles and included measures for investigating the causes of death and identification of bodies, and the Act on the Investigation of Cause of Death and on Identification of Bodies Handled by the Police, which recommended a procedure for death investigation, including a new autopsy system. The Death Investigation Promotion Program was to meant to be decided by the government in 2014. However, the relevant Act expired after it ran out of time. Later, in 2019, the Basic Act for Promotion of Death Investigation, the successor to the Promotion Act, was passed. This Act is significant because it sets the basic foundational principle and imposes plans created by the government. However, it remains unclear how these measures can be implemented, so further discussion and financial investment are now required.

The diatom test method using sodium hypochlorite (NaClO) was equivalent to the conventional method in water samples. However, the method using NaClO was inferior to the conventional method in lung samples, in which ethanol was used and the reaction with NaClO was longer compared with the method in water samples. Using water samples, we aimed to clarify whether these differences affect the diatom test result.Thirteen water samples from natural water sources were each divided into four parts corresponding to four (2 × 2) digestion methods: 3 "digestion" vs. 1 "digestion" and with ethanol vs. without ethanol. After the base-2 logarithmic transformation, the diatom counts were analyzed using three-way analysis of variance (ANOVA); factor 1 was "digestion times," factor 2 was "ethanol," and factor 3 was "sample number," and the interaction between factors 1 and 2 was also analyzed.The geometric means of the diatoms from the 3 "digestion" with ethanol method, the 3 "digestion" without ethanol method, the 1 "digestion" with ethanol method, and the 1 "digestion" without ethanol method were 373.5, 551.8, 436.6, and 522.0, respectively. ANOVA showed a significant difference in factor 2 (P = 1.7 × 10Ethanol may decrease the diatom count in the diatom test using NaClO. In contrast, the diatom frustules do not dissolve through three-times digestion using NaClO.

Stature estimation is one of the most basic and important methods of personal identification. The long bones of the limbs provide the most accurate stature estimation, with the femur being one of the most useful. In all the previously reported methods of stature estimation using computed tomography (CT) images of the femur, laborious manual measurement was necessary. A semi-automatic bone measuring method can simplify this process, so we firstly reported a stature estimation process using semi-automatic bone measurement software equipped with artificial intelligence. Multiple measurements of femurs of adult Japanese cadavers were performed using automatic three-dimensional reconstructed CT images of femurs. After manually setting four points on the femur, an automatic measurement was acquired. The relationships between stature and five femoral measurements, with acceptable intraobserver and interobserver errors, were analyzed with single regression analysis using the standard error of the estimate (SEE) and the coefficient of determination (R2). The maximum length of the femur (MLF) provided the lowest SEE and the highest R2; the SEE and R2 in all cadavers, males and females, respectively, were 3.913 cm (R2 = 0.842), 3.664 cm (R2 = 0.705), and 3.456 cm (R2 = 0.686) for MLF on the right femur, and 3.837 cm (R2 = 0.848), 3.667 cm (R2 = 0.705), and 3.384 cm (R2 = 0.699) for MLF on the left femur. These results were non-inferior to those of previous reports regarding stature estimation using the MLF. Stature estimation with this simple and time-saving method would be useful in forensic medical practice.

In recent years, Child Death Review (CDR) has attracted attention in Japan. It is necessary to consider not only hospital deaths but also out-of-hospital deaths. However, recommending preventive measures may be difficult because statistics on Japanese child mortality are limited. We examined cause of death (COD) and its application in preventive medicine based on death certificates (DCs) in the Chiba Prefecture. Death documents (DDs) and death slips (DSs) were created for individuals aged under 20 years who died between January 2012 and December 2016. They were based on DCs submitted to the Chiba Prefecture. We examined the trend of COD, occurrence of extrinsic mortality, and characteristics of doctors and compared CODs mentioned in DCs with autopsy results. For 1149 cases, the descriptions of DSs and DDs matched. Half of the extrinsic and undetermined deaths, which were examined by police doctors, occurred out-of-hospital. The autopsy rate was 13.5%. The COD mentioned in DCs did not match the autopsy results for 26 out of 69 autopsies performed at our institute. Approximately 70% of sudden infant death syndromes were diagnosed without autopsy. Low autopsy rate, incorrect writings, and errors during the death diagnosis cannot be ignored while conducting CDR. As more than half of the preventable deaths occurred out-of-hospital and there is no system to collect detailed information on them, the Japanese CDR system may not be reliable. It is necessary to improve the death investigation system by promoting autopsies for children and constructing a comprehensive database.

Postmortem computed tomography (PMCT) images help identify individuals and extract information from corpses. PMCT may substitute for a standard examination when bodies are severely damaged or when resources are limited in a mass fatality incident. In such situations, the dental information revealed by PMCT has the potential to narrow down candidates for identification further. However, the validity of the dental findings obtained from PMCT images remains unclear. In this study, we investigated the validity of dental findings on PMCT images compared to regular dental examinations as the reference standard. We routinely collected PMCT images of 148 unidentified corpses and compared the dental findings of each tooth obtained from PMCT with those of a regular dental examination. The validity of dental findings of PMCT was measured by sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). We also evaluated the accuracy of dental findings per corpse using 32 teeth as the denominator. The dental findings with high sensitivity and high specificity were a present tooth (0.96 and 0.97), a missing tooth (0.97 and 0.97), pontic (0.92 and 1.00), a dental implant (1.00 and 1.00), and a root filling (0.94 and 0.99). The mean accuracy of the dental findings per corpse in PMCT was 95.6% (standard deviation: 6.9, minimum ≤ median ≤ maximum: 65.6 ≤ 100 ≤ 100). The number of corpses with 100% accuracy in the dental findings was 81 (54.7%). The information obtained in this study highlights the potential use of PMCT during human identification in several settings with limited resources, such as the number of specialists present and the condition of the corpses.