At the Education and Research Center of Legal Medicine, Chiba University, we perform autopsies and various tests on dead people, mainly from Chiba prefecture, when a law enforcement agency has identified the need for a 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 regarding live individuals and conduct forensic diagnoses.

In 2014, the number of autopsies decreased greatly. The number of medicolegal autopsies performed at Chiba University has steadily increased over the past few years. However, 31 fewer autopsies were performed this year than last year. Although the reason for this decrease is unclear, one of the reasons is a decrease in reports made to the police. We cannot imagine an unnatural decrease in the number of deaths since the death rate and number of elderly people living alone increase every year. We hope that the causes of this decrease will be clarified and that some measures will be taken. Although the autopsies based on the new law increased by six bodies, we cannot expect that they will further increase because of fiscal affairs of Chiba prefecture.

In June 2014, the cabinet of Japan's government implemented a program to promote death investigations. This board was written into the program and should be held in each prefecture. However, it has not yet been implemented in most prefectures, including Chiba. Thus, this program does not seem to have adequate support from the government officials. Thus, there is scope for further improvements in death investigations

We not only collect relevant information about dead people, determine the exact cause of death of each individual, and identify bodies, but also clarify the death trends in Japan and help prevent accidents and disasters as well prevent the recurrence of murders and suicides; our social mission is to maintain and improve the safety and health of the population. Thus, here we aim to increase awareness of the present conditions by providing information about the cause of death and hope to contribute to system improvements by initiating the discussion of and modifying the manner in which the cause of death is investigated in our country.

Methods of classifying death causes and manners

In this report, the manner of death is classified as follows: natural, accident, suicide, homicide, undetermined external death, and undetermined death. We classified the cause of death as natural death by using the medium rank classification of the cause of death simple classification from the data obtained from the population dynamics survey conducted by the Ministry of Health, Labour and Welfare. We further classified accidental deaths into traffic accident, fall, drowning, asphyxia, fire, and other according to the results indicated on the corpse examination certificate. For cases of suicide, we used the classification by the Tokyo Metropolitan Medical Examiner's Office and classified the 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 referred to the classification used by the medical examiners in the United States and classified cases as child abuse, strangulation, sharp force, GSW, fire and thermal injury, blunt force, and other. Furthermore, we added "drop from a high place" to the homicide category. These words suggest that a mother dropped her child or baby from a high place before she herself jumped. 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 2014, the population of Chiba Prefecture was approximately 6,240,000; during that year, there were 53,970 deaths. The number of bodies reported to the police was 7,563 (7,334 to detectives and 229 to the traffic bureau). There were 335 judicial autopsies: 329 handled by the police (293 by detectives and 36 by the traffic bureau), two by the Chiba Coast Guard, three by the Chiba District Prosecution, and one by the Defense Army. There were 10 administrative autopsies, and 16 autopsies were performed based on the new act. The overall medicolegal autopsy rate was approximately 0.67%. Compared with the previous year, the total of 361 autopsies decreased by 64 (15.1%).

In our center, we performed a total of 335 medicolegal autopsies, including 309 judicial autopsies, 10 administrative autopsies, and 16 autopsies based on the new act. Among the judicial autopsies, 302 were commissioned by the Chiba Prefectural Police (269 by detectives and 33 by the traffic bureau), two were commissioned by the Chiba Coast Guard, three were commissioned by the Chiba Region Prosecution, one was commissioned by Defense Army, and one was commissioned by the Ibaraki Prefectural Police. We performed 15 postmortem examinations by computed tomography (CT); of them, three were requested by Chiba Prefecture and 12 were performed based on the new act.

In addition, regarding laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, blood biochemical tests, and others were performed in 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 performed CT imaging studies; thereafter, we performed the autopsy, obtained the various test results, enquired about the dead person's situation, and comprehensively estimated the cause and manner of death. Based on the cooperation agreement between Chiba and Tokyo University, we performed some of the drug and poison tests at Tokyo University.

With respect to the services of forensic odontology and forensic genetics, we confirmed the identity of the unidentified remains using dental knowledge and DNA testing. 


Judicial autopsies

Table 1 shows the nationality of the corpses. There were seven foreign corpses from five countries.

Table 2 indicates the manner of death. There were 64 (21%) natural deaths, 101 (33%) unexpected accidents, 34 (11%) suicides, 31 (10%) homicides, 19 (6%) deaths by undetermined external causes, and 60 (19%) deaths that occurred for unknown reasons. Overall, there were approximately 2.3 times more male than female casualties. Although there was not much difference in the number of male versus female homicide victims, more males than females died by all other causes of death.

Tables 3 and 4 indicate the age distribution of the corpses. Individuals > 55 years of age accounted for 58% of all cases, and the average age was 57 years. Of all the manners of death, the average age of homicide victims was the youngest at 40 years. This is because many of the victims were babies or children. There were no significant differences in manner of death among the different calendar months, but fewer autopsies were required in April, July, and August.

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 58% of the total deaths, were malignant neoplasms (cancer), heart trouble, pneumonia, and cerebrovascular disease. Although individuals aged > 65 years accounted for the majority of natural deaths, those aged 35-54 years tended to die suddenly from either a heart attack or a cerebrovascular disease. Two deaths of drugs and poison were caused or presumed caused by new psychoactive substances (NPS), which became an object of public concern. We detected α-pyrrolidinovalerophenone in one body and 251NBOMe in another. Although two more cases were suspected to be caused by NPS, we could not confirm this.

Tables 7 and 8 indicate the causes of accidental deaths. In terms of accidental deaths, the leading cause in 2014 was traffic accidents, followed by fires, whereas in 2013, fires were the most common, followed by traffic accidents. The next most common causes of accidental death were falls, drugs and poisoning, and drowning. 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 of age.

Tables 9 and 10 indicate the suicide methods. The most common means of suicide was hanging, followed by drowning and then drugs and poisoning. The suicide rate of elderly individuals was strikingly higher than that in the previous year.

Tables 11 and 12 indicate the homicide methods. Homicides involving death by a blunt object were most common in the current and previous year. In this report, we newly added a method, drop from a high place. In this year, two mothers dropped their sons and daughters from high places before killing themselves. This is a means of homicide with suicide. In this year, including dropped cases, seven people killed a total of nine people before he or she killed him- or herself. In the current year, the ages of the killed persons spanned the generations.


Among the deaths cause by undetermined external causes (19 bodies), 11 died of drowning and two died 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 (60 bodies), it was difficult to identify the cause of death in 51 because of bleached bone, corpse wax, mummification, or a high degree of decomposition. In the remaining cases, we could determine neither the internal nor the external cause. For example, if someone collapsed from a heart attack in the bathtub and got drowned, although the cause of death was drowning in the bathtub, the underlying cause could not be found.

In terms 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, 15 children or babies < 18 years were autopsied, among whom one died of natural causes, one of an accident, eight were killed, and four died of undetermined causes. The number of homicidal deaths was remarkable (four in the last year). Four children were dropped from high places by their two mothers as mentioned above, one was killed in the car of carbon monoxide poisoning by his mother who killed herself at the same time, one was asphyxiated by her mother who intended to die with her but failed, and the other two died of abuse. Three of the undetermined deaths were newborn babies, the bodies of whom featured bleached bones or a high degree of decomposition.

Administrative autopsies

Among the corpses in which autopsies were performed for administrative purposes, seven were male and three were female. Their mean age was 51 years (range, 21-80 years). There were eight natural, one accidental, and one undetermined cause of death. Of the eight natural deaths, five resulted from a heart attack.

There were 10 natural and 4 accidental deaths. Of the 10 natural deaths, 3 were the result of a heart attack.


Autopsies based on the act of death identification and investigation (the new act)

Among the 16 corpses, 10 were male and six were female. One was Chinese. Their mean age was 47 years (range, 9 months to 87 years). There were 10 natural deaths, three accidental deaths, one suicide, one undetermined external cause, and one undetermined death.


CT examinations

CT examinations were performed on 15 corpses: three for administrative purposes and 12 based on the new act. Of the former three examinations, two were performed on men and one was performed on a woman. Among these, one cause of natural death was determined.

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


Forensic odontology

On request from the Chiba Prefectural Police and the Chiba Coast Guard, we carried out two dental exams to identify the bodies. We also performed dental exams for many other corpses without formal request.


Forensic genetics

Because the National Police Agency decided to test DNA typing in crime laboratories, we were not requested to do DNA typing tests by the Chiba Prefectural Police. However, we performed DNA typing tests on request by 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 the child consultation centers, we report the incidence of child abuse and domestic violence. In the current year, there were a total of 19 cases: 16 from the child consultation centers and three from the Chiba District Public Prosecutors Office, the Chiba Prefectural Police, and a city in Chiba Prefecture. We have submitted a report to or answered each organization.