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.

Looking at the number of autopsies, the total number increased by 63 from last year, exceeding the record number of 2013, which was the highest number ever, and it was the most record as Chiba University. Regarding judicial autopsy, although it does not reach past figures, the fact that the autopsies in compliance with the Death Investigation and Identification Act (the new Act) annually increases contributes to the overall increase. However, as described later, the number of deaths has also increased, and the autopsy rate is not rising.

In June 2014, the Government of Japan implemented a program to promote death investigations. Prompted to act as result of this program, a committee dedicated to the promotion of death investigations in the Chiba Prefecture was established in March 2016, and the third meeting was held in March 2018. However, we had to wait a year for another meeting. Thus far, addressing issues related to death investigations has not been easy.

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 2017, the population of the Chiba Prefecture was approximately 6,256,000; there were 56,396 deaths. The number of bodies reported to the police was 8,277 (8,048 to detectives and 229 to the traffic bureau). There were 337 judicial autopsies (increased by 18.1%): 326 handled by the police (286 by detectives and 40 by the traffic bureau), 5 by the Coast Guard (Chiba and Choshi), and 6 by the Chiba District Prosecution. There were 15 administrative autopsies. Thirty-six autopsies were performed in compliance with the new Act. The total number of medicolegal autopsy was 388, and autopsy rate per all the dead people was approximately 0.6%. Compared with the previous year, there was an increase of 64 (19.8%) in the total number.

In our Center, we performed a total of 367 medicolegal autopsies in 2017, including 317 judicial autopsies, 14 administrative autopsies, and 32 autopsies in compliance with the new Act. Of the judicial autopsies, 295 were commissioned by the Chiba Prefectural Police (259 by detectives and 36 by the traffic bureau), 5 by the Coast Guard (Chiba and Choshi), 6 by the Chiba District Prosecution, and 11 by the Ibaraki Prefectural Police. We performed 8 postmortem examinations using computed tomography (CT).

Regarding laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, blood biochemical tests, and other tests as may be needed are performed on all corpses from which a specimen can be obtained. Where needed, we examine bodies for signs of carbon monoxide poisoning and the presence of plankton and sperm. We first perform CT imaging studies, after which we perform the autopsy, obtain the various test results, investigate the dead person’s situation, and comprehensively estimate the cause and manner of death. Following a cooperation agreement between Chiba and Tokyo University, we perform drug and poison tests at Tokyo University.

With respect to the services of forensic odontology and forensic genetics, we confirm the identity of unidentified remains using dental records and DNA testing. However, as a rule, the DNA type testing of police handled corpses is conducted at the crime laboratory, so there was no request from the Chiba prefectural police. In addition to the request from the Coast Guard, we are also cooperating in the testing of cases other than Chiba based on cooperation agreements with other universities.

Regarding clinical forensic medicine, we received 37 requests from child consultation centers in Chiba Prefecture and Chiba City, Chiba Prefectural Police, and Chiba District Prosecution, and conducted forensic diagnoses accordingly.


Judicial autopsies

Table 1. shows the nationality of the corpses. There were 7 foreign corpses from 6 countries.

Table 2. indicates the manner of death. There were 44 (14%) natural deaths, 93 (29%) unexpected accidents, 53 (17%) suicides, 19 (6%) homicides, 30 (9%) deaths through undetermined external causes, and 78 (25%) deaths that occurred for unknown reasons. In 2017, the rates of accidental deaths and homicidal death were less than the averages in comparable years. Overall, there were approximately 2.3 times more male than female fatalities. Many more males than females died due to the classified causes of death.

Tables 3. indicates the age distribution of the corpses. Individuals older than 64 years of age accounted for 50% of all deaths, and the average age was 61 years. For the manner of death overall, in comparable years, the average ages of suicides and homicide victims were lower. However, in 1917 average ages of all the manners were similar. the lower, at 46 years.

Table 4. indicates the month distribution. Although there were no significant differences in the manner of death among the different calendar months, in the winter months we had more corpses than in the other seasons.

Tables 5. and 6. indicate the causes of natural deaths. Although the number of deaths was too small to describe general tendencies, circulatory diseases including heart disease and aortic dissection were prominent. Individuals aged 65 years and older accounted for 50%. However, younger aged tended to die suddenly from circulatory diseases.

Tables 7. and 8. indicate the causes of accidental deaths. In 2017, the leading cause was fire, and traffic accidents were fewer than in comparable years. Most of the accidental deaths owing to drugs and poisoning were related to amphetamine. There were also accidental deaths due to heatstroke and hypothermia, and work-relate deaths, which do not fit within the precisely specified categories. More than 70% of deaths through fire occurred among people 65 years of age and older, because they could not escape from the fire danger in time.

Tables 9. and 10. indicate the suicide methods. The most common means of suicide was hanging similar to that of national statistics. However, drowning was following closely. There were some drowning cases in undetermined external manner which could not be classified to suicide clearly. We might say it is because of a particular reason that Chiba Prefecture is surrounded by the sea. In 2017, in terms of age, the people who died due to suicide were spread across all age groups, and most elderly people aged 65 to 75 years old.

Tables 11. and 12. indicate the homicide and its methods. Nineteen was the smallest number of homicides these six years. It is possible that the decreasing trend of homicide reflects this result. Homicides involving death through strangulation, blunt force, and sharp force were common in 2017. In terms of age, homicide victims were spread across all age groups and the average of age had risen, partly because dead children including victims of homicide-suicide by mothers (only one case in 2017) were less than in comparable years.


Among deaths due to undetermined external causes (30 bodies), 16 died of drowning. Regarding the other cases including death of fire, although we determined the direct causes of death, the manner of death (whether accident, suicide, or homicide) could not be determined.

Among the deaths that occurred for unknown reasons (78 bodies), it was difficult to identify the cause of death in 48 cases because of their bleached bones, corpse wax, mummification, or high degree of decomposition. In the remaining cases, we could determine neither internal nor external causes of death.

In 2017, autopsies were performed on 20 children or babies (under 18 years old), among whom 5 died of natural causes, 1 from accident, 2 from homicide, and 9 from undetermined causes. Among the 9 who died from undetermined causes, 5 died by infant sudden death and 3 were killed as an unborn baby or a new-born.

Administrative autopsies

Among the 14 corpses on which autopsies were performed for administrative purposes, 7 were male and also 7 were female. Their average age was 37 years (range, 1 month to 91 years), which was smaller than that of other types of autopsies, and ages were spread. There were 9 cases of natural death, 2 accidental deaths, and 3 undetermined cause of death. As in comparable years, most of the corpses autopsied in this category died from natural causes, but all the deaths of undetermined cause were infant sudden deaths.


Autopsies performed in compliance with the Death Investigation and Identification Act (the new act)

Among the 36 corpses autopsied, 24 were male and 12 were female. Their average age was 55 years (range, 5 months to 88 years). There were 17 natural deaths, 8 accidental deaths, 3 suicidal deaths, 2 undetermined external causes of death, and 6 deaths from an undetermined cause. All the three suicidal deaths were related to drugs and poisoning.


CT examinations

CT examinations were performed on 8 corpses and we performed a subsequent autopsy (judicial) on 5 of the corpses. CT examinations were conducted prior to the autopsy in all cases, including judicial, administrative autopsies, and autopsies under the new act, and the radiologists belonging to the center read the medical images.


Forensic odontology

On the request of the Coast Guard, we carried out dental examinations to identify bodies. And we examined the teeth of all other unidentified bodies (78 cases) without a formal request. Moreover because of the cooperation agreement between Chiba and Tokyo Medical and Dental University, we are cooperative with the staff of the university in this regard.


Forensic genetics

We performed DNA typing tests at the request of the Coast Guard, law courts and nonofficial organizations. Moreover, because of the cooperation agreement between Chiba and Tokyo University, we performed DNA typing tests that the Tokyo District Public Prosecutors Office requested of Tokyo University.


Forensic Toxicology

For all the bodies that can collect specimens, a toxic substance test using a mass spectrometer is carried out. The main drugs detected this year are as follows.


Clinical forensic medicine

At the request of child consultation centers, we report the incidence of child abuse and domestic violence. In 2017, there were 18 cases. Additionally, the Chiba District Public Prosecutors Office and the Chiba Prefectural Police consulted us concerning 19 injury cases. We have submitted reports or answered the inquiries of each organization.


DVI training

In November 2017 we conducted training to prepare for large-scale disasters (DVI [Disaster victim identification] training). Under the assumption that the airplane failed to land at the airport and flames up, observation / examination, dentistry findings, DNA / fingerprints etc. were taken by police officers, medical doctors, dentists, public servants, and forensic pathologists.