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.

If the police and medical investigators do not work closely together on each case, the exact cause and the manner of death cannot be determined. In such cases, under the Japanese system, in approximately 90% cases of unnatural deaths, the doctor who performs the post-mortem examination on a body has to decide the cause and manner of death, even when evidence is unavailable, so that the cause of death can be included on the corpse examination certificate. Hence, in most cases, we do not know exactly who decides the cause and manner of death. Accordingly, the manner of death reported in such cases is determined from a mainly medical point of view and is determined without access to sufficient information about the dead person, and it should be noted that this system is different from those in European forensic institutes, which takes direct responsibility to determine the cause of death, and that of other organized professional groups such as coroners and medical examiners in the United Kingdom, the United States, and many other countries.

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. However, we have not necessarily been able to reach the point where forensic medicine helps the society, and such information is currently not being accumulated in our country. 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 2012, the population of the Chiba Pref. was approximately 6,200,000, and during this time, there were approximately 53,200 deaths. The number of bodies reported to the police was 8,398 (8,158 detectives, 240 traffic), and of these, 407 bodies were autopsied. Among these, judicial autopsies handled by the police accounted for 391 cases (336 detectives, 58 traffic), the Chiba Coast Guard handled 5 cases, and the Chiba Region Prosecution handled 2 cases. The other 9 autopsies were performed for administrative purposes, which required the consent of the family of the deceased. The overall medico-legal autopsy rate was approximately 0.77%.

On the other hand, in our department, we performed a total of 353 medico-legal autopsies, including 344 judicial and 9 administrative autopsies. Among the judicial autopsies, 334, 5, 2, 3 were commissioned by the Chiba Prefectural Police (292 detectives, 42 traffic), Chiba Coast Guard, Chiba Region Prosecution, and Ibaraki Prefectural Police, respectively. Moreover, we performed 17 post-mortem examinations by computed tomography (CT). Among these, 16 and 1 were requested by the Chiba Prefecture and Tokyo Metropolitan area, respectively.

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 and one DNA test.


Judicial autopsies

Table 1 shows the nationality of the corpses. There were 9 foreign corpses from 6 countries.

Table 2. As for the manner of death, there were 71 (20.6%) cases of natural death, 125 (36.3%) unexpected accidents, 56 (16.3%) suicides, 22 (6.4%) homicides, 20 (5.8%) undetermined external causes, and 50 (14.5%) unknown deaths. Overall, there were approximately 2.5 times more male than female dead bodies; however, more female than male person were homicide victims.

Tables 3 and 4. According to the age distribution of the bodies, 55-84-year-olds accounted for 51.4% of all cases, while most people who had dies because of suicide were aged around 50 years old. As for the manner of death according to the month of year, we found that there were no meaningful differences.

Tables 5 and 6. Natural deaths were divided into various diseases, as were the general causes of death. However, there were also some cases of sudden deaths, including heart attacks in this group. Moreover, there were five cases of malnutrition (death from starvation), and this was characteristic. According to the age distinction, people aged 50 to 84 years old accounted for 47.9% of all cases of natural deaths.

Tables 7 and 8. The majority of deaths from accidents were caused by fire, followed by traffic accidents. This was quite different from the report of the Tokyo Metropolitan Medical Examiner's Office, which reported that falling was the number one cause of accidental death, followed by asphyxia. According to age, people aged between 64 and 84 years old accounted for the majority of cases.

Tables 9 and 10. In the majority of cases, the means of suicide were hanging and drowning. However, in comparison with the report of the Tokyo Metropolitan Medical Examiner's Office, the differences were remarkable. For example, the rate of asphyxia in Tokyo was 64%, while that in Chiba was 32%; and the rate of jumping from a high place was only 1% in Chiba, as compared to 16% in Tokyo. However, we speculate that the number of autopsies performed may have influenced the observed differences.

Tables 11 and 12. As for the means of homicide, it varied considerably. Generally, in our country, deaths by strangulation and sharp force are thought to be the most common, but death by blunt force was observed at approximately the same ratio in our department. Moreover, many of these victims were females, although this parameter was too small for us to be able to make a meaningful interpretation.


Administrative autopsies

The nine corpses in which autopsies were performed for administrative purposes were all male. Their mean age was 62.1 years, with the lowest and highest ages being 38 and 88 years, respectively. The manners of deaths were as follows: natural, 6; accident, 1; undetermined, 2.


CT examinations

CT examinations were performed in 17 corpses; of these, 14 were male and 3 were female. The highest age was 86 years, the lowest was 33, 2 bodies were of unknown age, and the average age was 69.7 years. We could estimate the cause of death in 2 bodies (homicide by sharp force and aortic aneurysm explosion), and we suggested possible causes of death for additional 7 bodies (all were natural). In addition, as for the CT, we carry out examinations before the autopsies for all corpses.


Dental examinations

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