At the Education and Research Center of Legal Medicine, Chiba University, we perform autopsies and various tests on the deceased, mainly from the Chiba Prefecture, in cases where a law enforcement agency has identified the need for forensic investigation, and we determine the cause of death from a medical point of view. We also perform DNA tests and dental examinations to identify a body. Furthermore, we receive requests from child consultation centers and prosecution teams regarding live individuals and then conduct forensic diagnoses.

Considering the number of autopsies, the total number increased by 72 from 2017, setting a record for Chiba University. Moreover, judicial autopsies had the highest number, but the annual increase in autopsies in compliance with the Death Investigation and Identification Act (hereafter “the Investigation Act”) contributed to the overall increase. However, the increase in autopsies has been proportional to the number of deaths, except the stagnation period from 2014 to 2016, and we cannot confirm that the autopsy rate in Chiba Prefecture is higher than that in other prefectures.

Based on the program that promotes death investigations in June 2014, a committee dedicated to the promotion of death investigations in the Chiba Prefecture was established in March 2016. However, outstanding results have not yet been obtained. On the contrary, the basic act on the promotion of death investigation is going to be enforced in April 2020. We hope that death investigation measures will progress in the future.

We not only collect relevant information on dead people, determine the exact cause of death of each individual, and identify bodies; we also clarify the death trends in Japan and help prevent accidents and disasters, as well 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 present challenges through providing information on the causes of death, and we hope to contribute to system improvements through initiating constructive discussion 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 follows: natural, accidental, suicide, homicide, undetermined external cause, and undetermined. We classify the cause of death as natural death, using the medium rank classification of the simple classification for cause of death, based on vital statistics data obtained from the Ministry of Health, Labour and Welfare. We further classify accidental deaths into traffic accidents, falls, drowning, asphyxiation, fire, and other causes, according to the results indicated on the corpse examination certificate. For cases of suicide, 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 cases of homicide, 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. Although many countries use 5 classifications for specifying the manner of death, here in Japan, where the manner of death for many unidentified bodies remains undetermined, we use the category “undetermined external death” for cases in which we do not know the manner of death but can determine the direct cause of death, such as drowning.



In 2018, the population of the Chiba Prefecture was approximately 6,270,000, and there were 59,514 deaths in this prefecture. In total, 8,681 deaths were reported to the police, 84,449 to detectives, and 232 to the traffic bureau. There were 396 judicial autopsies, indicating a 25.5% increase; 391 were handled by the police (349 by detectives and 42 by the traffic bureau), 2 by the Coast Guard (Kisarazu and Choshi), and 3 by the Chiba District Prosecution. There were 19 administrative autopsies. Seventy-two autopsies were performed in compliance with the Investigation Act. The total number of medicolegal autopsies was 487, and the autopsy rate per all deaths was approximately 0.8%. Compared to 2017, the total number of autopsies increased by 99 (25.5%).

A total of 439 medicolegal autopsies, including 350 judicial autopsies, 19 administrative autopsies, and 70 autopsies in compliance with the Investigation Act, were performed in 2018 at our center. Among the judicial autopsies, 337 were commissioned by Chiba Prefectural Police (300 by detectives and 37 by the traffic bureau), 2 by the Coast Guard (Kisarazu and Choshi), 3 by the Chiba District Prosecution, and 8 by the Ibaraki Prefectural Police. We performed 6 postmortem examinations using computed tomography (CT).

Until 2017, police general doctors, entrusted by the police, performed all death external examination services in Chiba Prefecture. However, in 2018 (fiscal year), the forensic pathologists in the center began to perform some of the services under the jurisdiction of Chiba Central Police Office instead of general doctors in 10 patients.

Regarding laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, blood biochemical tests, and other tests, as required, were performed in all corpses, and specimens were obtained. Where required, we examined the bodies for signs of carbon monoxide poisoning and the presence of plankton and sperm. First, we performed CT imaging studies; subsequently, we performed autopsy, obtained various test results, investigated the dead person’s situation, and comprehensively estimated the cause and manner of death.

With respect to the services of forensic odontology and forensic genetics, we confirmed the identity of the unidentified human remains using dental records and deoxyribonucleic acid (DNA) testing. However, as a rule, DNA type testing of corpses handled by a police was conducted at the crime laboratory, so there was no request for this service from the Chiba Prefectural Police. In addition to the requests from the Coast Guard, we incorporated in the testing of cases other than those in Chiba, according to the cooperation agreements with other universities.

Regarding clinical forensic medicine, we received 40 requests from child consultation centers in Chiba Prefecture and Chiba City, and from Chiba Prefectural Police and Chiba District Prosecution. We established forensic diagnoses accordingly.

“Chiba Child Death Reviews” were held three times by pediatricians, other physicians, and government and judicial officials in the prefecture organized by this center to share information on death cases of children and discuss how to prevent recurrence.


Judicial autopsies

Judicial autopsies were performed on 345 bodies this year. (There were 350 cases in the overview, but a difference was observed because there were those who seemed to be the same person, such as a broken body.) The contents are outlined below.

Table 1 shows the nationality of corpses handled by our center in 2018. There were 10 foreign corpses from 3 areas.

Table 2 indicates the manner of death of all corpses handled by our center. There were 43 (13%) natural deaths, 108 (31%) accidents, 45 (13%) suicides, 25 (7%) homicides, 45 (13%) deaths from undetermined external causes, and 79 (23%) deaths that occurred for unknown reasons. In 2018, the tendencies were similar to the averages in the previous years. Overall, there were approximately 2.2 times more male than female fatalities. Many more males than females died due to the above-classified causes of death except homicides.

Table 3 indicates the age distribution of the corpses handled by our center. Individuals greater than 64 years old accounted for 44% of all deaths, which was less than that in the previous years. The average age was 59 years, and the median age was 60 years. For the manner of death, overall, the average age for suicide was 53 years, and that for homicidal deaths was 49 years, both of which were comparatively lower. However, in 1918, the average age for natural deaths and accidents was greater than 60 years.

Table 4 indicates the monthly distribution of deaths by manner and number of deaths. Although there were no significant differences in the manners of death by calendar month, in 2018, it was unusual that the number of deaths in March was the highest.

Tables 5 and 6 indicate the causes of natural death. Although the number of deaths was too small to describe general results, circulatory diseases, including heart disease, cerebrovascular disease, and aortic dissection, were predominant. Deaths among individuals aged greater than 65 years accounted for 50% of deaths from natural causes. However, younger people tended to die suddenly from circulatory diseases. In the case of judicial autopsy, people who would normally receive medical treatment died alone because they were not being referred. Although not listed, there were several deaths each year due to malnutrition and dehydration.

Tables 7 and 8 indicate the causes of accidental death. In 2018, the leading cause of death was related to fire, and traffic accidents and drugs and poisoning were the second. Most accidental deaths due to drugs and poisoning were related to amphetamine, similar to the previous year. There were also a number of accidental deaths due to heatstroke and hypothermia and work-related deaths, which do not fit within the precisely specified categories. Approximately 70% of deaths due to fire were observed among people greater than 65 years old because they were unable to escape the fire danger in time.

Tables 9 and 10 indicate the methods of suicide. The most common means of suicide was hanging, similar to the national statistics of Japan. However, hanging was closely followed by drowning. There were some cases of drowning due to an undetermined external manner, which could not be clearly classified as suicide. In 2018, people who died due to suicide were distributed across all age groups.

Tables 11 and 12 indicate homicide deaths and methods. Although in the previous year, the number of homicides was less, in 2018, it returned to the average level. Homicides involving death through strangulation, sharp force trauma, and blunt force trauma were common in 2018. Regarding age, homicide victims were distributed across all age groups. The average age was lower than that in 2017, but elderly victims aged greater than 75 years were significantly predominant this year.


Among the 45 deaths due to undetermined external causes, 13 died from drowning and 6 from fire. Regarding the other cases, although we determined the direct causes of death, the manner of death (whether accident, suicide, or homicide) could not be determined.

Among the 79 deaths that occurred for unknown reasons, it was difficult to identify the cause of death in 50 cases due to bleached bones, corpse wax, mummification, or a high degree of decomposition of the body. In the remaining cases, we could not determine either the internal or external causes of death.

In 2018, autopsies were performed in 13 children (less than 18 years old) or infants. Among whom, 1 died of suicide, 4 due to homicide, 1 from undetermined external causes, and 7 from undetermined causes. Two out of the 4 cases of homicides were considered homicide-suicide (the murderer killed oneself after the homicide), and 1 case of homicide was considered infanticide. Among those who died from undetermined causes, 3 died due to sudden infant death and 4 died as an unborn or newborn infant.

Administrative autopsies

Among the 19 corpses on which autopsies were performed for administrative purposes, 15 were male and 4 were female. Both the average age and the median age were 59 years (range, 17?95 years). There were 10 cases of natural death, 4 accidental deaths, 2 suicides, 1 undetermined external death, and 2 undetermined cause of death. Similar with the previous years, most corpses autopsied in this category were classified as having natural cause of death, and in many cases, the bereaved requested the body to be autopsied.


Autopsies performed in compliance with the Investigation Act

The number of cases in this category significantly increased compared to that in 2017, from 36 to 70. Among the 70 corpses autopsied, 51 were male and 19 were female. The average age was 50 years, and the median age was 56 years (range, 25 days to 88 years). Regarding manner of deaths, greater than half had natural deaths, and the ratio was relatively close to administrative autopsy (Table 13). Among the natural deaths, there were 12 cardiovascular diseases, 10 cerebrovascular diseases, and 3 malignant neoplasms. All seven cases of suicide involved drug poisoning or carbon monoxide poisoning. The distribution of age (Table 14) was also not significantly different from other categories, except for the sudden deaths of the infants.

There were 9 deaths of children or infants less than 18 years old, with 1 natural death (pneumonia), 1 accidental death (drowning in the bathtub), and 7 unknown deaths. All unknown deaths were sudden deaths of less than 1-year-old infants.


Computed tomography examinations

CT examinations were performed on 6 corpses, and we performed a subsequent autopsy (judicial) on 5 of these 6 corpses. CT examinations were performed prior to the autopsies, including judicial autopsies, administrative autopsies, and autopsies under the new Act, in all corpses. Radiologists in our center read the CT images. Moreover, although it is still at the research stage, magnetic resonance imaging was also performed.


Forensic odontology

Based on the request of Chiba Prefectural Police and the Coast Guard, we conducted dental examinations to identify the bodies. With the absence of formal request, we examined the teeth of all other unidentified bodies. And, because of the cooperation agreement between Chiba University and Tokyo Medical and Dental University (TMDU), we worked together with the TMDU staff in this regard to conduct dental examinations of the bodies autopsied in the University of Tokyo (UT) and the International University of Health and Welfare (IUHW). Moreover, we conducted dental examinations of almost all cases requested by child consultation centers to our center.


Forensic genetics

We performed DNA typing tests based on the request of the Coast Guard, courts of law, and nonofficial organizations. Moreover, because of the cooperation agreement between Chiba University and the UT, we performed DNA typing tests as requested by the UT, the Tokyo District Public Prosecutors Office, or the Metropolitan Police Department.


Forensic toxicology

In our center, toxic substance tests using mass spectrometers(Gas Chromatography and Mass Spectroscopy [GC/MS], Liquid Chromatography-Tandem Mass Spectrometry [LC/MS/MS], Liquid Chromatography-Quadruple Time of Flight Mass Spectrometry [LC/QTOF-MS]) were performed for all bodies, and specimens were obtained. Furthermore, we performed toxic substance tests as requested by the UT and the IUHW according to the cooperation agreement. The main drugs detected in 2018 are mentioned in the table (Table 15).


Clinical forensic medicine

Based on the request of child consultation centers, our center was involved in reporting the incidence of child abuse and domestic violence. In 2018, there were 23 cases of child abuse and domestic violence. Additionally, the Chiba District Public Prosecutors Office and Chiba Prefectural Police referred a total of 17 injury cases in our center. We have submitted reports or responded to the inquiries of each organization.


Chiba Child Death Reviews

In the 8th meeting in January, three cases that had already been examined for medical diagnosis in the past workshop were reviewed from the viewpoint of preventing recurrence.

In the 9th meeting in May, Matsudo City Hospital delivered a lecture on the outpatient behavior. Three case studies were conducted to discuss the medical and social background.

In the 10th meeting in September, a lecture on Child Death Review initiatives in Yokohama was delivered. Four case studies were conducted to discuss mainly the social background.  

Disaster victim identification training

Although we planned to conduct disaster victim identification training to prepare for large-scale disasters in September 2018, we had to cancel it due to bad weather.