At the Education and Research Center of Legal Medicine, Chiba University, we perform autopsies and various tests on the deceased, mainly from Chiba Prefecture, when 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. Further, we receive requests from child consultation centers and prosecution teams regarding live individuals and then conduct forensic diagnoses.

In 2015, the number of autopsies was as large as in the previous year. Although the number of medicolegal autopsies performed at Chiba University had increased over the last several years, 2014 saw a great reduction, further reduced by one case in 2015. This trend of decrease has continued. Autopsy statistics in Japan from 2014 to 2015 show a decrease in judicial autopsies, replaced by autopsies on the Act of Death Investigation and Identification (the new act). The number of autopsies based on the new act depends on prefectural finances because each prefecture has to pay the greater part of this type of autopsy. In Chiba Prefecture, as we cannot expect a large increase in the budget, we are afraid that, in consequence, the number of medicolegal autopsies will decrease. From the perspective of progress in death investigation, we are extremely anxious about the current trends.

In June 2014, the Cabinet of Japan implemented a program to promote death investigations. Based on this program, the committee on the promotion of death investigations in Chiba Prefecture was established in March 2016. However, we cannot expect the committee to discuss innovative and positive issues because the officials of Chiba Prefecture seem unwilling to do so. Thus, the problems related to death investigations are not easy to solve.

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. Thus, we aim to increase awareness of the present conditions by providing information on causes of death and hope to contribute to system improvements by initiating the discussion of and modifying the manner in which cause of death is investigated in our country.

Methods of classifying causes and manners of death

In this report, the manner of death is classified as follows: natural, accident, 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 data obtained from vital statistics conducted by the Ministry of Health, Labour and Welfare. We further classify accidental deaths into traffic accident, fall, drowning, asphyxiation, fire, and other according to the results indicated on the corpse examination certificate. For cases of suicide, we use the classification by the Tokyo Metropolitan Medical Examiner’s Office and classify cases as hanging, sharp force, gunshot wound (GSW), drugs and poisoning, drowning, means of moving vehicle, thermal injury, jumping from a high place, and others. For cases of homicide, we refer to the classification used by the medical examiners in the United States and classify cases as child abuse, strangulation, sharp force, GSW, fire and thermal injury, blunt force, drop from a high place, and other. Although many countries use five classifications for the manner of death, here in Japan, where the manner of death of 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 2015, the population of Chiba Prefecture was approximately 6,224,000; in the same year, there were 56,073 deaths. The number of bodies reported to the police was 7,883 (7,652 to detectives and 231 to the traffic bureau). There were 327 judicial autopsies: 321 handled by the police (275 by detectives and 46 by the traffic bureau), three by the Chiba Coast Guard, and three by the Chiba District Prosecution. There were twelve administrative autopsies. Eighteen autopsies were performed based on the new act. The overall medicolegal autopsy rate was approximately 0.6%. Compared with the previous year, the total number of autopsies (357) decreased by 4 (1.1%).

In our Center, we performed a total of 334 medicolegal autopsies in 2015, including 304 judicial autopsies, 12 administrative autopsies, and 18 autopsies based on the new act. Of the judicial autopsies, 292 were commissioned by the Chiba Prefectural Police (252 by detectives and 40 by the traffic bureau), three by the Chiba Coast Guard, three by the Chiba District Prosecution, and six by the Ibaraki Prefectural Police. We performed 10 postmortem examinations by computed tomography (CT). 

Regarding laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, blood biochemical tests, and others are performed on all corpses from which a specimen could be obtained; as needed, we examined the bodies for signs of carbon monoxide poisoning and the presence of plankton and sperm. We first perform CT imaging studies; thereafter, we perform the autopsy, obtain the various test results, investigate the dead person’s situation, and comprehensively estimate the cause and manner of death. Based on the 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. 

Regarding clinical forensic medicine, this was the third year since implementation began. We received 26 requests from child consultation centers in Chiba Prefecture and Chiba City, Chiba, Chiba Prefectural Police, and Chiba District Prosecution, and then conducted forensic diagnoses.


Judicial autopsies

Table 1 shows the nationality of the corpses. There were 11 foreign corpses from six countries.

Table 2 indicates the manner of death. There were 46 (15%) natural deaths, 122 (40%) unexpected accidents, 27 (9%) suicides, 27 (9%) homicides, 26 (8%) deaths by undetermined external causes, and 46 (15%) deaths that occurred for unknown reasons. In the current year, the number of unexpected accidents is larger than the average in the last three years in common years. Overall, there were approximately 2.1 times more male than female casualties. More males than females died by all other causes of death except homicide, which claimed more female victims than males.

Tables 3 and 4 indicate the age distribution of the corpses. Individuals older than 55 years of age accounted for 62% of all cases, and the average age was 58 years. Of all the manners of death, the average age of homicide victims was the youngest, at 46 years. This is because many of the victims were babies or children. The average age of suicide was the next youngest at 50 years, because relatively young people around 40 years died by suicide. There were no significant differences in manner of death among the different calendar months, but fewer autopsies were required in July, August, and November.

Tables 5 and 6 indicate the causes of natural deaths divided into various diseases that were the general causes of death. The four main causes of death, which accounted for 50% of the total deaths, were malignant neoplasms (cancer), heart trouble, pneumonia, and cerebrovascular disease. Although individuals aged 55 years and older accounted for the majority of natural deaths, those aged 35?54 years tended to die suddenly from a heart attack.

Tables 7 and 8 indicate the causes of accidental deaths. In 2015, the leading cause was traffic accidents, followed by fires, a trend that was seen in the previous year as well. There were also accidental deaths caused by heatstroke and hypothermia, and labor, which do not fit into the former categories. The majority of accidental deaths occurred in people > 65 years old. In the current year, the number of labor-related deaths of foreigners was remarkable.

Tables 9 and 10 indicate the suicide methods. The most common means of suicide was drowning, followed by drugs and poisoning and thermal injury. The number of hangings, which is the most common method in suicide statistics, was not as large as that of the previous year. The suicide rate among people aged 35 to 44 years was higher compared with other age groups.

Tables 11 and 12 indicate the homicide methods. Homicides involving death by strangulation, sharp force, and blunt force were common in the current year. Children aged 0 to 4 years became victims in suicide-homicide cases. In the current year, many of relatively older people, or those aged 55 to 74 years, were killed.


Among deaths due to undetermined external causes (26 bodies), 16 died of drowning and four, of fire. Regarding the other six, although we determined the direct causes of death, the manner of death (accident, suicide, or homicide) could not be determined.

Among the deaths that occurred for unknown reasons (46 bodies), it was difficult to identify the cause of death in 30 because of their bleached bone, corpse wax, mummification, or high degree of decomposition. In the remaining cases, we could determine neither internal nor external causes. For example, if a pregnant woman suddenly drops her baby, it is often hard to distinguish natural death from external death.

In terms of the deaths in detective facilities in the current year, there were three cases, all of which occurred in police cells in detentions.

In the current year, 14 children or babies (18 years old and younger) were autopsied, among whom one died of natural causes, one from an accident, four from a homicide, and seven from undetermined causes. Four babies’ deaths with undetermined causes occurred before or soon after childbirth.

Administrative autopsies

Among the corpses on which autopsies were performed for administrative purposes, nine were male and three were female. Their mean age was 55 years (range, three months to 86 years). There were nine cases of natural, two accidental, and one undetermined cause of death.


Autopsies based on the Act of Death Investigation and Identification (the new act)

Among the 18 corpses, 12 were male and one was female, who was a foreigner. Their mean age was 47 years (range, 13 days to 85 years). There were seven natural deaths, ten accidental deaths, and one death from an undetermined cause.


CT examinations

CT examinations were performed on 10 corpses. However, eight corpses were autopsied after. The manners of death of bodies not autopsied were internal and undetermined.

CT examinations were conducted prior to the autopsy in all cases.


Forensic odontology

On the request of the Chiba Coast Guard, we carried out seven dental exams to identify bodies. We also performed dental exams for many other corpses without a formal request.


Forensic genetics

As the National Police Agency decided to test DNA typing in crime laboratories, we were not requested to perform DNA typing tests by the Chiba Prefectural Police. However, we performed DNA typing tests on the request of law courts and nonofficial organizations. Moreover, based on the cooperation agreement between Chiba and Tokyo University, we performed DNA typing tests that the Tokyo District Public Prosecutors Office requested of Tokyo University.


Clinical forensic medicine

Upon request from child consultation centers, we report the incidence of child abuse and domestic violence. In the current year, there were a total of 26 cases: 15 from child consultation centers and 11 from the Chiba District Public Prosecutors Office. We have submitted a report to or answered the inquiries of each organization.