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.

Compared with the total number of autopsies performed in 2018, 439, the total number of autopsies performed in 2019 was 412. The number of judicial autopsies performed was higher in 2019 than in 2018, and this number was the highest recorded number to date. However, the number of autopsies performed in compliance with the Death Investigation and Identification Act (hereafter “the Investigation Act”) and administrative autopsies contributed to the overall decline in numbers. Although several factors could have contributed to this finding, the decline in the Investigation Act could be attributed to the fact that autopsies were performed throughout the year at the International University of Health and Welfare established in Narita City in 2017, and the number of autopsies performed did not decrease in Chiba Prefecture considered in its entirety. However, based on the overall trend, we observed that the number of autopsies performed was proportional to the increase in the number of deaths; therefore, it cannot be claimed that the autopsy rate was higher than that observed in other prefectures.

Based on the program that promotes death investigations in June 2014, a committee dedicated to the promotion of death investigations in the Chiba Prefecture was established in March 2016. However, outstanding results have not yet been obtained. On the other hand, the Basic Act on the Promotion of Death Investigation was put in force in April 2020. We hope that death investigation measures will progress in the future.

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 2019, the population of Chiba Prefecture was approximately 6,280,000 with 62,164 deaths reported in this prefecture. Overall, 9,019 deaths were reported to the Police Department, 8,777 to detectives, and 242 to the Traffic Bureau. The number of judicial autopsies performed was 439, which represents a 10.9% increase over those performed during the previous year; 431 were managed by the Police Department (396 by detectives and 35 by the Traffic Bureau), 4 by the Coast Guard (Chiba and Choshi), and 4 by the Chiba District Prosecution. Among all autopsies performed during this year, 9 were administrative autopsies. Forty-six autopsies were performed in compliance with the Investigation Act. The total number of medicolegal autopsies was 494, and the autopsy rate per all deaths was approximately 0.8%. Compared with 2018, the total number of autopsies increased by 7 (1.4%).

Overall, 412 medicolegal autopsies were performed at our center in 2019, which represents a 6.2% decline compared with the previous year. These autopsies included 363 judicial autopsies, 9 administrative autopsies, and 40 autopsies performed in compliance with the Investigation Act. Among the judicial autopsies, 347 were commissioned by the Chiba Prefectural Police (322 by detectives and 25 by the Traffic Bureau), 4 by the Coast Guard (Chiba and Choshi), 4 by the Chiba District Prosecution, and 8 by the Ibaraki Prefectural Police Department. We performed 4 postmortem examinations using computed tomography (CT).

In 2018 (fiscal year), the forensic pathologists in the center began to perform some of the services under the jurisdiction of Chiba Central Police Office instead of general doctors. They performed 16 patients in 2019.

Regarding laboratory examinations, drug and poison tests, pathology organization inspection, blood typing, blood biochemical tests, and other tests, as required, were performed in all corpses, and specimens were obtained. Where required, we examined the bodies for signs of carbon monoxide poisoning and the presence of plankton and sperm. First, we performed CT imaging studies; subsequently, we performed autopsy, obtained various test results, investigated the dead person’s situation, and comprehensively estimated the cause and manner of death.

With respect to the services of forensic odontology and forensic genetics, we confirmed the identity of the unidentified human remains using dental records and deoxyribonucleic acid (DNA) testing. However, as a rule, DNA type testing of corpses handled by a police was conducted at the crime laboratory, so there was no request for this service from the Chiba Prefectural Police. In addition to the requests from the Coast Guard, we incorporated in the testing of cases other than those in Chiba, according to the cooperation agreements with other universities.

Regarding clinical forensic medicine, we received 98 requests from child consultation centers in Chiba Prefecture and Chiba City, and from Chiba Prefectural Police and Chiba District Prosecution. We established forensic diagnoses accordingly.

“Chiba Child Death Reviews (Chiba CDR)” were held three times by pediatricians, other physicians, and government and judicial officials in the prefecture organized by this center to share information on death cases of children and discuss how to prevent recurrence.


Judicial autopsies

During 2019, judicial autopsies were performed on 361 corpses. There were 363 cases in the overview, but a difference was observed because there were those who seemed to be the same person, such as a broken body.) The details are outlined below.

Table 1 shows the nationality of the corpses managed by our center in 2019. We identified 13 corpses of foreign nationals in 3 areas.

Table 2 shows the manner of death of all corpses managed by our center. We recorded 57 (16%) natural deaths, 101 (28%) accidents, 61 (17%) suicides, 19 (5%) homicides, 36 (10%) deaths associated with undetermined external causes, and 87 (24%) deaths associated with an unknown cause. In 2019, we observed a lower rate of homicidal but higher rate of suicidal deaths than the averages in previous years. Overall, the fatality rate was approximately 2.2-fold higher in men than in women. The death rate secondary to the aforementioned causes (except homicides) was higher in men than in women.

Table 3 shows the age distribution of corpses managed by our center. The total number of individuals aged >65 years was 57%, which represents a significant percentage of elderly individuals. The mean and median ages were 60 and 67 years, respectively. The mean age based on the cause of death was 53 years in cases of suicidal deaths and 58 years in cases of homicidal deaths (which were relatively low), 66 years in cases of natural death, and 62 years in cases of accidental deaths.

Table 4 shows the monthly distribution of deaths based on the manner and number of deaths. Evaluation of the number of cases by month showed that most deaths occurred between January and April.

Tables 5 and 6 show the causes of natural death. Although the number of deaths was too low to accurately describe results, causes of natural death were similar to those contributing to the overall mortality statistics of the population (heart disease, cerebrovascular disease, malignant neoplasm, and pneumonia). We observed that 50% of deaths attributable to natural causes occurred in those aged >64 years. However, sudden death associated with circulatory diseases was a trend observed in younger individuals. Some deaths were attributable to undernutrition and dehydration.

Tables 7 and 8 show the causes of accidental death. In 2019, fires were observed to be the leading cause of death, followed by traffic accidents and drowning. A large number of accidental deaths were attributed to heat stroke, hypothermia, and work-related deaths, which did not meet the criteria for specific categories. Approximately two-thirds of deaths associated with fires occurred in individuals aged >65 years, primarily because they were unable to escape in time.

Tables 9 and 10 indicate the methods of suicide. The most common means of suicide was hanging, similar to the statistics of National Police agency. However, hanging was closely followed by drowning. We identified some cases of drowning associated with an undetermined external manner, which could not clearly be classified as suicide. In 2019, we observed that suicidal deaths were distributed across all age groups.

Tables 11 and 12 list the homicidal deaths recorded in this year and the methods used. Although the number of homicidal deaths was lesser than those recorded in the previous year, the percentage of women who died by homicide was higher than the average in previous years. Homicides involving sharp and blunt force injuries, as well as strangulation were common in 2019. Homicidal deaths were distributed across all age groups.


Among the 36 deaths that occurred secondary to undetermined external causes, 16 were attributed to drowning and 1 to a fire. With regard to the other cases, although we could determine the direct cause of death, the manner of death (accident, suicide, or homicide) remained undetermined.

Among the 86 deaths that occurred secondary to unknown causes, it was difficult to identify the cause of death in 64 cases owing to bleached bones, corpse wax, mummification, or significantly decomposed corpses. In the remaining cases, we could not accurately attribute the cause of death to internal or external factors.

Administrative autopsies

Among the 9 corpses on which autopsies were performed for administrative purposes, 6 were men and 3 were women. The mean and median ages were 55 and 53 years, respectively. We observed 6 cases of natural death, 1 case of accidental death, 1 case of death attributed to an undetermined external cause, and 1 case of death attributed to an undetermined cause. Most deaths in this category were classified as natural deaths, and in many cases, the bereaved families requested that an autopsy be performed. These data were similar to those recorded during the previous year.


Autopsies performed in compliance with the Investigation Act

Compared with the 70 autopsies performed during the previous year, the number of autopsies performed during 2019 was 40. Among the 40 corpses that underwent autopsies, 24 were men and 16 were women. The mean and median ages were 55 and 51 years, respectively. With regard to the manner of death, most deaths were attributed to natural causes, followed by deaths secondary to undetermined causes (Table 13). Among the natural deaths, 3, 3, and 4 were attributable to cardiovascular, cerebrovascular, and gastrointestinal diseases, respectively. Among deaths secondary to undetermined causes, 5 deaths were categorized as sudden deaths that occurred in young and middle-aged adults. Five of the 6 suicidal deaths involved drug or carbon monoxide poisoning. Compared with the age distribution of corpses that underwent judicial autopsies (Table 14), corpses that underwent administrative autopsies were usually aged 35?54 years. We speculate that middle-aged individuals who were not involved in crimes but in whom causes of death remained undetermined underwent autopsies under this category. Based on statistical data showing the number of autopsies performed per month (Table 15), we observed a significant difference between the early and latter months of this year (2019). Among the cases of natural death, 16 of 30 (53%) occurred in the first half of the year and only 1 of 10 (10%) in the second half.


Child deaths

In 2019, autopsies were performed in 21 children (aged <18 years) or in infants. Among these, 20 were judicial and 1 was in compliance with the Investigation Act. One, 4, 2, 3, and 11 deaths were attributed to natural, accidental, homicidal, undetermined external causes, and undetermined causes. Nine of the deaths attributed to undetermined causes were categorized as sudden infant deaths.


Computed tomography examinations

CT examinations were performed on 4 corpses, and we performed a subsequent autopsy (judicial) on 3 of these 4 corpses. CT examinations were performed prior to the autopsies, including judicial autopsies, administrative autopsies, and autopsies under the new Act, in all corpses. Radiologists in our center read the CT images. Moreover, although it is still at the research stage, magnetic resonance imaging was also performed.


Forensic odontology

Based on the request of Chiba Prefectural Police and the Coast Guard, we conducted dental examinations to identify the bodies. With the absence of formal request, we examined the teeth of all other unidentified bodies. And, because of the cooperation agreement between Chiba University and Tokyo Medical and Dental University (TMDU), we worked together with the TMDU staff in this regard to conduct dental examinations of the bodies autopsied in the University of Tokyo (UT) and the International University of Health and Welfare (IUHW). Moreover, we conducted dental examinations of almost all cases requested by child consultation centers to our center.


Forensic genetics

We performed DNA typing tests based on the request of the Coast Guard, courts of law, and nonofficial organizations. Moreover, because of the cooperation agreement between Chiba University and the UT, we performed DNA typing tests as requested by the UT, the Tokyo District Public Prosecutors Office, or the Metropolitan Police Department.


Forensic toxicology

In our center, toxic substance tests using mass spectrometers(Gas Chromatography and Mass Spectroscopy [GC/MS], Liquid Chromatography-Tandem Mass Spectrometry [LC/MS/MS], Liquid Chromatography-Quadruple Time of Flight Mass Spectrometry [LC/QTOF-MS]) were performed for all bodies, and specimens were obtained. Furthermore, we performed toxic substance tests as requested by the UT and the IUHW according to the cooperation agreement. The main drugs detected in 2019 are mentioned in the table (Table 16).


Clinical forensic medicine

Based on requests from child consultation centers, our center was involved in reporting child abuse and domestic violence. In 2019, we recorded 68 cases of child abuse and domestic violence. Additionally, the Chiba District Public Prosecutor’s Office and the Chiba Prefectural Police Department referred a total of 30 cases with injuries to our center. We submitted reports or responded to the inquiries of each organization that approached us. We established a Clinical Forensic Medicine Outpatient Department for pediatric patients at Chiba University Hospital in July 2018. We have improved our evaluation system in collaboration with the Department of Forensic Medicine and the Department of Pediatrics at the University Hospital. Moreover, we have upgraded our evaluation system, and in collaboration with other specialized divisions, we are involved in investigation of abuse-induced injuries.


Chiba Child Death Reviews

At the 11th meeting in January, in addition to two case studies, we introduced a case of administrative autopsy, before which the forensic pathologist explained the need for the autopsy and the procedure to the bereaved family We sponsored a case study group of participating facilities in Chiba Prefecture for research regarding feasibility verification for the establishment of a registration and CDR system for child death cases, by the Japan Pediatric Society Child Death Registration Review Committee.

At the 12th meeting in May, we organized a study session on the Basic Act on the Promotion of Death Investigation and homicide-suicide (homicidal death followed by suicide). Additionally, in three autopsy cases, death was attributed to the actions of a perpetrator with a suspected psychiatric illness. Medical and social backgrounds were discussed in these cases.

At the 13th meeting in September, we delivered a lecture discussing the role of the CDR performed by the Department of Forensic Medicine, Kyoto University. We performed a study of three cases of homicide-suicide involving parents with childcare neurosis, improper parenting skills, and mental illness and primarily focused on the social background of these individuals.

Disaster victim identification training

In June 2019, we organized an emergency preparedness training program for large-scale disasters (the Disaster Victim Identification drill), at the School of Medicine, International Medical and Welfare University newly established in Narita City. Considering flood damage including landslides and inundation, we arranged bereaved family training that included local government staff (which was implemented for the first time). Approximately 100 participants attended this program and received training regarding disaster preparedness and response activities.