At the department of legal medicine, Chiba University, we perform autopsies and various tests on dead people, mainly from the Chiba prefecture, when a law enforcement agency, such as the police, has judged the necessity of a forensic investigation, and we determine the cause of death from a medical point of view. Moreover, we also perform DNA tests and dental examinations in order to identify a body. Furthermore, we receive requests from child consultation centers etc. regarding living bodies and conducting forensic diagnoses.

In April 2013, the Act on the Investigation of Cause of Death and on Identification of Bodies Handled by the Police (hereafter referred to as the "act of death identification and investigation") was brought into force, and since then, autopsies have been conducted to comply with the act. The act of death identification and investigation prescribes that the police have a responsibility to investigate and identify causes of death, and that forensic examinations can be performed on bodies in cases where there is a low possibility of criminal involvement. As such, the number of autopsies will increase, and the presence of a medical examiner system should correct regional disparities. Although the purpose of the death identification and investigation act has not necessarily been accomplished, and we do not believe that the act is definitely applied in some prefectures, we hope that the act will change the system of death investigation in the future. Moreover, postmortem examinations by computed tomography (CT) can be performed under the new act. In our Chiba University department, although we have examined 4 bodies by CT, we were unable to identify the cause of death in 3 and so we performed autopsies.

As we commented in the last report, we not only collect relevant information about dead people, determine the exact cause of death of each individual, and identify bodies, but we also clarify the trend of deaths in the Japan and help in the prevention of accidents and disasters and in 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 regarding the cause of death, and we hope to contribute to the improvement in the system by initiating such an argument and thereby modify the manner in which the cause of death is investigated in our country.


Methods of classifying the causes and manners of death

In this report, the manner of death was 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 almost during population dynamics survey by the Ministry of Health, Labor, and Welfare. In terms of accidental deaths, we further classified them into traffic accident, fall, drowning, asphyxia, fire, and others, according to the results indicated on the corpse examination certificate. In terms 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. In terms 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 others. Although many countries use five classifications of the manner of death, in view of our country specifically, in which the manner of death of many unidentified bodies remains undetermined, we have distinguished undetermined external death, in which we do not know the manner of death but can determine the direct cause of death, such as drowning.



In 2013, the population of Chiba Prefecture was approximately 6,190,000, and during the year, there were 53,772 deaths. The number of bodies reported to the police was 7,876 (7,619 to detectives and 257 to the traffic bureau), and of these, 424 bodies were autopsied. Judicial autopsies handled by the police accounted for 395 of these cases (344 by detectives and 51 by the traffic bureau), the Chiba Coast Guard handled 4 cases, and the Chiba Region Prosecution handled 5 cases. There were 14 administrative autopsies, and 10 autopsies were performed based on the new act. The overall medicolegal autopsy rate was approximately 0.79%. In comparison with the previous year, the number of the bodies reported to the police decreased by 539 (6.6%), but the total number of autopsies increased by 17 (4.2%).

In our department, we performed a total of 366 medicolegal autopsies, including 342 judicial autopsies, 14 administrative autopsies, and 10 autopsies based on the new act. Among the judicial autopsies, 331 were commissioned by the Chiba Prefectural Police (292 by detectives and 39 by the traffic bureau), 3 were commissioned by the Chiba Coast Guard, 5 were commissioned by the Chiba Region Prosecution, and 3 were commissioned by the Ibaraki Prefectural Police. We performed 10 postmortem examinations by CT; of these, 6 were requested by Chiba Prefecture and 4 were performed based on the new act.

In addition, as for the laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, and blood biochemical tests, among others, were performed in all corpses from which a specimen could be obtained, and as needed, we examined the bodies for signs of carbon monoxide poisoning and the presence of plankton and sperm. Before performing an autopsy, we first carried out imaging studies by CT; thereafter, we performed the autopsy, obtained the various test results, enquired about situations of the dead person, and comprehensively estimated the cause and manner of death.

Concerning the identifications of the bodies, we carried out two dental exams.


Judicial autopsies

Table 1 shows the nationality of the corpses. There were 6 foreign corpses from 5 countries.

Table 2 indicates the manner of death. There were 57 (16.7%) natural deaths, 133 (38.9%) unexpected accidents, 54 (15.8%) suicides, 29 (8.5%) homicides, 19 (5.6%) deaths by undetermined external causes, and 50 (14.6%) deaths that occurred for unknown reasons. Overall, there were approximately 2.5 times more male than female casualties. Although there were more female than male homicide victims last year, in 2013, 41% of the homicide victims were female.

Tables 3 and 4 indicate the age distribution of the bodies. Individuals over 55 years of age accounted for 56% of all cases. The majority of suicide victims were aged around 50 years. There were no significant differences regarding the manner of death in different calendar months.

Tables 5 and 6 indicate the causes of natural deaths, which were divided into various diseases, as were the general causes of death. The 4 main causes of death, which accounted for 56% of the total deaths, were malignant neoplasms (cancer), heart trouble, pneumonia, and cerebrovascular disease. Although individuals aged more than 65 years accounted for the majority of natural deaths, individuals aged 35-54 years tended to die suddenly from either a heart attack or cerebrovascular disease.

Tables 7 and 8 indicate the causes of accidental deaths. The majority of deaths from accidents were caused by fire, which is the same as the previous year. Traffic accidents were the second most prevalent cause of accidental deaths. Deaths caused by falling and asphyxia, which account for the majority of accidental deaths in the Tokyo Metropolitan region, were relatively few. The third most prevalent cause of death was drowning. There were also accidental deaths caused by heatstroke and hypothermia, and related to labor, which do not fit into the former categories. The majority of accidental deaths occurred in people aged over 65.

Tables 9 and 10 indicate the suicide methods. The most common means of suicide was drowning, and drugs and poison were the second most common methods. Hanging, which was most common last year, was the third most common means of suicide. However, this does not indicate that there has been a reduction in the number of deaths caused by hanging; it is likely that drowned and poisoned bodies were referred for judicial autopsies at a higher rate.

Tables 11 and 12 indicate the homicide methods, which varied greatly. Generally, in our country, death by strangulation and sharp objects are thought to be most common. However, homicides involving death by a blunt object were most common (45%) in our department. However, this parameter was too small for us to be able to make any meaningful interpretations.


Among the deaths cause by undetermined external causes (19 bodies), 15 died from drowning. As for the other 4, although we determined the direct causes of death, for example asphyxiation, the manner of death (accident, suicide, or homicide) could not be determined.

Among the deaths which occurred for unknown reasons (50 bodies), it was difficult to search for the cause of death in 35 cases because of bleached bone, corpse wax, mummification, or high decomposition. There were 5 cases in which death was thought to have occurred suddenly, although we could not determine the cause. There were 4 new-born babies. In the remaining cases, we could determine neither the internal nor external cause, for example, although the cause of death was drowning in the bathtub, the underlying cause could not be found.

Administrative autopsies

Among the corpses in which autopsies were performed for administrative purposes, 8 were male and 6 were female. Their mean age was 42 years, with the lowest and highest ages being 2 weeks and 79 years, respectively.

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 10 corpses, 7 were male and 3 were female. Their mean age was 48.9 years, with the lowest and highest ages being 21 and 70 years, respectively.

There were 5 natural deaths, 2 accidental deaths, 1 suicide, and 1 undetermined death. Of the 5 natural deaths, 3 were the result of a heart attack.


CT examinations

CT examinations were performed on 10 corpses. There were 6 that were performed for administrative purposes and 4 that were based on the new act. Of these 4, 2 were judicial autopsies and 1 was a new act autopsy. As such, only 1 body was examined only by CT. Of the former 6 examinations, 5 were performed on men and 1 was performed on a woman. The mean age was 65.3 years, and the lowest and highest ages were 48 and 96 years, respectively. Among these, 1 cause of death was determined (internal cerebrovascular disease) and the causes of 4 others were inferred (3 natural deaths and 1 drowning); the cause of the remaining death was not determined, and there were several possible causes. In the case of the 1 corpse examined by CT, based on the new act, the cause of death was accidental asphyxiation.

For all of the corpses, the CT examinations were conducted prior to the autopsy.


Dental examinations

According to the request from the Chiba Prefectural Police, we carried out two dental exams in order to determine birth and parentage. In addition, we performed dental exams and DNA typing for many other corpses without formal request.


Clinical forensic medicine

At the request of child consultation centers etc., we report the incidence of child abuse and domestic violence. In this year, there were 13 cases in total. Of these, 12 cases were from the child consultation center, and 1 case was from Chiba District Public Prosecutors Office. We have submitted the report to each of these.