Preface

At the Education and Research Center of Legal Medicine (Chiba University), we perform autopsies and various tests on deceased individuals, mainly from Chiba Prefecture, when law enforcement agencies identify the need for forensic investigation. Our objective is to determine the cause of death from a medical perspective. We perform DNA analyses and dental examinations for the purpose of body identification, furthermore, we receive requests for forensic diagnoses from child consultation centers, prosecution teams, and prefectural police regarding living individuals.

In 2023, the total number of autopsies conducted was 420, marking an increase of 30 compared to the 390 autopsies performed at Chiba University in 2022. Compared to the previous year, the number of administrative autopsies decreased and the number of judicial autopsies increased, reaching a record high at Chiba University. The number of CT examinations and clinical forensic cases had also increased; making 2023 a busy year for our department.

The Basic Act for the Promotion of Death Investigation came into effect in April 2020. Although the second round of discussions is underway at the Promotion Council to promote the policy, we cannot expect any new projects requiring budgetary measures, and discussions on system reforms are at a standstill. In addition, with regard to Child Death Review, the model project does not cover autopsy cases, so there is a strong possibility that appropriate consideration will not be given to cases of abuse, accidents, or suicides.

Notably, we not only collect relevant information on dead people, determine the exact cause of death of each individual, and identify bodies, but also determine the death trends in Japan and help prevent accidents and disasters as well as the recurrence of murders and suicides. Our social mission is to maintain and improve the safety and health of the population. Given this context, we aim to increase awareness of the present challenges by providing information on the causes of death, and hope to contribute to system improvements by initiating constructive discussions leading to modifications in how causes of death are investigated in our country.

Classifying the manner and causes of death

In this report, the manner of death is classified as natural, accidental, suicide, homicide, undetermined external cause, and undetermined. For the cause of death deemed as “natural,” we employ the medium rank classification from the simple classification of causes, drawing on vital statistics data obtained from the Ministry of Health, Labour, and Welfare. Accidental deaths are further subdivided based on the results indicated on the corpse examination certificate, such as traffic accidents, falls, drowning, asphyxiation, fire, and other causes. For suicide cases, we use the classification of the Tokyo Metropolitan Medical Examiner’s Office and classify cases as hanging, sharp force, gunshot wound (GSW), drugs and poisoning, drowning, use of a moving vehicle, thermal injury, jumping from a high place, and other causes. For homicide cases, we refer to the classification used by medical examiners in the United States and classify cases as child abuse, strangulation, sharp force, GSW, fire and thermal injury, blunt force, and other causes. However, in 2023, we only had three measures. While many countries use five classifications to specify the manner of death, in Japan, owing to a significant proportion of unidentified bodies with undetermined manners of death, we introduce the “undetermined external death” category. This is reserved for cases in which the manner of death is unknown, but its direct cause can be determined, such as drowning.

　

Overview

In 2023, the population of Chiba Prefecture was approximately 6,270,000. A total of 73,721 deaths were reported in this prefecture; 10,941 deaths were reported to the police department, 10,756 to detectives, and 185 to the Traffic Bureau. In total, 629 judicial autopsies were performed, representing a 21.4% increase from the previous year. Overall, 615 deaths were managed by the police department, 12 by the Coast Guard, and 3 by the Chiba District Prosecution. Among all autopsies performed during the year, five were administrative autopsies. A total of 84 autopsies were performed in accordance with the Investigation Act, 719 medicolegal autopsies were performed, and the autopsy rate per death was approximately 1.1% (the rate in Japan was approximately 1.2%).

Overall, 430 medicolegal autopsies were performed at our center in 2023, representing a 10.3% increase over the previous year. These autopsies included 408 judicial autopsies, 5 administrative autopsies, and 17 autopsies performed in compliance with the Investigation Act. Among the judicial autopsies, 403 were commissioned by the Chiba Prefectural Police (393 by detectives and 10 by the Traffic Bureau), 3 by the Chiba District Prosecution, and 3 by the Ibaraki Prefectural Police Department. The Traffic Bureau handled the five administrative autopsies.

In the fiscal year 2018, forensic pathologists in the center, instead of physicians, began to perform some services under the jurisdiction of the Chiba Central Police Office. They performed 22 postmortem examinations in 2023. Apart from autopsies, forensic radiologists performed 46 postmortem examinations using computed tomography (CT).

Laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, blood biochemical tests, and other tests were performed on all corpses as required, and specimens were obtained. Where required, the bodies were examined for signs of carbon monoxide poisoning and for the presence of plankton and sperm. First, we performed CT imaging studies; subsequently, we performed autopsies, obtained various test results, investigated the condition of the deceased, and comprehensively estimated the cause and manner of death.

With respect to forensic odontology and genetics, we confirmed the identity of unidentified human remains using dental records and DNA testing. However, as a rule, DNA-type testing of corpses handled by the police had to be conducted at a crime laboratory. Therefore, the Chiba Prefectural Police did not request this service. We incorporated testing of cases other than those in Chiba according to cooperative agreements with other universities.

Regarding clinical forensic medicine, we received 107 requests from child consultation centers in Chiba Prefecture, Chiba City, Chiba Prefectural Police, and Chiba District Prosecution. Accordingly, we established the forensic diagnosis.

　

Nationalities

Table 1 shows the nationalities of the corpses managed by our center in 2023. Fourteen participants were foreign nationals from six regions (Southeast Asia 4, East Asia 4, North America 2, South America 2, South Asia 1, and Africa 1).

Judicial autopsies

In 2023, judicial autopsies were performed on 408 corpses. The details are outlined in the following tables.

Table 2 shows the manner of death of all the corpses managed by our center. We recorded 78 (19%) natural deaths, 121 (30%) accidents, 95 (23%) suicides, 8 (2%) homicides, 28 (7%) deaths associated with undetermined external causes, and 78 (19%) deaths due to unknown causes. It is noteworthy that the number of homicides has decreased significantly compared to previous years. The fatality rate was approximately 2.2 times higher in men than in women, and men outnumbered women in all manners of death except for homicides and deaths associated with undetermined external causes.

Table 3 shows the age distribution of the corpses managed at our center. The mean and median ages were 58 and 70 years, respectively, showing little difference from the previous years. The mean ages based on the cause of death were 48 years for suicide, 66 years for homicide, 64 years for natural death, and 65 years for accidental death.

Table 4 shows the monthly distribution of deaths based on type and number of deaths. Although the number was slightly higher in March, no significant difference was observed.

Tables 5 and 6 show the causes of the natural deaths. Although the number of deaths was too low to describe the results accurately, the causes of natural deaths were similar to those that contributed to the overall mortality statistics of the population (heart disease, malignant neoplasm, and cerebrovascular disease). In addition, many behavioral disorders are caused by malnutrition and dehydration. We observed that two-thirds of the deaths attributable to natural causes occurred in patients aged >64 years old.

Tables 7 and 8 list the causes of accidental deaths. In 2023, fires were observed to be the leading cause of death, as in previous years, followed by other accidental deaths, drownings, and falls. Many other accidental deaths were attributed to heat stroke, hypothermia, work-related deaths which did not meet the criteria for a specific category, and medical accidents. In terms of drugs and poisoning, eight of the 14 cases involved stimulants. By age group, the average age in fire incidents was 76 years, and the damage caused by elderly people’s delay in evacuation was conspicuous. Furthermore, 2023 witnessed a relatively higher number of falls, with a mean age of 73 years.

Tables 9 and 10 list suicide methods. There were more suicide cases than the previous years. As there has not been a sharp increase in suicides nationwide, this increase is likely due to a change in the judgment of the prefectural police. The most common means of suicide were hanging, followed by drugs and poisoning, with 17 out of 26 cases being carbon monoxide poisoning using charcoal briquettes. This was followed by drowning and jumping. In terms of sex distribution, men were the majority in Chiba Prefecture. National statistics show an increase in the percentage of female suicides. Age-wise, the deceased were widely distributed, ranging from teenagers to people in their 80s.

Tables 11 and 12 list the homicidal deaths recorded in 2023 and the methods used. The number of homicide cases dropped significantly from 21 cases in the previous year to 8 cases. This is a welcome result of the improved public safety situation in the Chiba Prefecture. However, this may be only a temporary phenomenon. Regarding the means of homicides, blunt force was the most common, and the number of victims of men and women was the same, but it was not enough to judge anything, including the age distribution.

Among the 28 deaths due to undetermined external causes, 11 were attributed to drowning and two to fire. Regarding the other cases, although we could determine the direct cause of death, the manner of death (accident, suicide, or homicide) remained undetermined.

Among the 78 deaths due to unknown causes, the cause of death was difficult to identify in 66 cases due to bleached bones, corpse wax, mummification, or significantly decomposed corpses, including one case suspected to be suicide.

　

Administrative autopsies

All five bodies examined in this year were male. Their ages ranged from 49 to 96 years, with a mean and median age of 70 and 72 years, respectively. We observed 1 case of natural death, 2 cases of accidental death, and 1 case of unknown death. This differs from the usual trend of more internal causes. As the number of autopsies performed in compliance with the Investigation Act increases, bereaved families requested more bodies be sent for administrative autopsies. Although the number of autopsies this year was low, all were cases in which the bereaved families requested an autopsy to determine the cause of death.

　

Autopsies performed in compliance with the Investigation Act

In 2023, 17 autopsies were performed in compliance with the Investigation Act, which is a relatively modest number. One reason for this is that the number of autopsies has increased in the International University of Health and Welfare and Nippon Medical School, which was relocated to Chiba Prefecture. Eleven of the 17 autopsies were on men and six on women; their ages ranged from 0 to 90 years, and the mean and median ages were 56 and 55 years, respectively. Regarding the manner of death, most deaths were attributed to natural causes, followed by accidental death (Table 13). Although these cases did not require judicial autopsies, we assumed the autopsies had been performed in certain instances to confirm the cause of death.

　

Child deaths

In 2023, autopsies were performed on 13 children (aged <18 years) or infants. Among these, 12 autopsies were judicial, and one was under the Investigation Act; 3 deaths were attributed to natural causes, 3 to accidents, 5 to suicides, and 1 to an unknown cause. All five suicides were committed by people aged 15 years or older, out of which four were women.

　

CT examinations

CT examinations without autopsies were performed on 46 corpses in 2023. However, in all corpses, CT examinations were performed prior to autopsies, including judicial, administrative, and autopsies under the Investigation Act. In addition, approximately 80 readings were performed, including individual identification by imaging, readings of biomedical images related to clinical forensics, and readings of CT images acquired at other institutions. Magnetic resonance imaging (MRI) has also been adopted, although it is still in the research stage.

　

Forensic odontology

Dental findings were collected and recorded in appraisal reports for almost all forensic autopsies of unidentified bodies. In addition, based on a partnership agreement, we collected dental findings from unidentified corpses that had undergone forensic autopsies at the University of Tokyo (UT) and the International University of Health and Welfare, together with the Department of Forensic Dentistry, Tokyo Medical and Dental University (which was changed to the Institute of Science, Tokyo). A case study meeting was held twice a year under a comprehensive partnership agreement with the Chiba Dental Association. In the child guidance center cases requested by our center, we performed intraoral evaluations in cases that required intraoral findings, such as multiple dental caries and bite marks.

　

Forensic genetics

DNA testing is performed for personal identification and paternity testing at the request of courts and non-official organizations. Moreover, because of the cooperation agreement between Chiba University and the UT, we performed DNA typing tests as requested by the UT, Tokyo District Public Prosecutors Office, and the Metropolitan Police Department.

　

Forensic toxicology

In addition to simple tests conducted on all bodies from which samples can be collected, drug toxicology tests using mass spectrometers (GC/MS, LC/MS/MS, LC/QTOF-MS) were also implemented (qualitative and quantitative analyses when necessary). Moreover, based on this cooperation agreement, we have been conducting drug and toxicology tests associated with autopsies performed at the UT. The primary drugs detected at Chiba University in 2023 are listed in Table 14. Amphetamine and methamphetamine were both detected in 14 stimulant-related cases, returning to the top 10.

　

Clinical forensic medicine

At the request of the child consultation centers in Chiba Prefecture, Chiba City, and Edogawa Ward, we submitted 81 written opinions related to child abuse and domestic violence. In addition, we received and responded to 26 consultations on injury cases from the Chiba District Prosecution and Chiba Prefectural Police, among others. In July 2018, a clinical forensic outpatient department was opened within the Pediatric Division of Chiba University Hospital. The hospital’s pediatric and forensic departments cooperated to enhance the examination system. With the cooperation of other specialized departments, we aim to ascertain injuries caused by abuse, among other causes.

　

Chiba CDR

Every year, we hold the Chiba Child Death Review (CCDR), and experts in Chiba Prefecture, including pediatricians, government officials, and the judiciary, share information on child death cases and hold discussions on how to prevent their recurrence. On July 15, 2023, we hosted the 16th meeting at the School of Medicine, Chiba University. After a lecture on CDR from the perspective of a legal scholar and an examination of cases of infant and fetal deaths in Chiba Prefecture, a limited number of participants heard a report and discussed a case involving a girl who died due to refusing medical treatment for religious reason. Approximately 70 people, including members of the Chiba District Public Prosecutors Office and the Chiba Prefectural Police, participated in this meeting.

　

Disaster victim identification training

The fifth Chiba Large-Scale Disaster (DVI [Disaster victim identification] drill) training was held at the School of Medicine, Chiba University, in February 2023. Assuming flooding and landslides caused by heavy rain, in cooperation with the Department of Legal Medicine of the International University of Health and Welfare and co-hosted by the Chiba Prefectural Medical Association and the Chiba Prefectural Dental Association, training was conducted using dolls to check autopsy examinations and identification procedures during disasters, together with the Chiba Prefectural Police, Chiba Prefectural Disaster Prevention and Crisis Management Department, neighboring municipalities, and Chiba Coast Guard.