千葉 文子

In this study, we assessed the sexual dimorphism of the contemporary Japanese skull and established sex discriminant function equations based on cranial measurements using three-dimensional (3D) computed tomography (CT) images. The CT images of 263 corpses (142 males, 121 females) that underwent postmortem CT scanning and subsequent forensic autopsy were evaluated. Twenty-one cranial measurements were obtained from 3D CT reconstructed images, which extracted only bone data. We performed descriptive statistics and discriminant function analyses for the measurements. Nineteen measurements were significantly larger in males, suggesting sexual dimorphism of the Japanese skulls. Univariate discriminant function analyses using these measurements showed a sex classification accuracy of 57.8-88.2%, and bizygomatic breadth provided the highest correct prediction rate. Multivariate discriminant function analyses offered the most accurate model using seven variables with an estimation rate of 93.9%. Our results suggest that cranial measurements based on 3D CT images may help in the sex estimation of unidentified bodies in a contemporary Japanese population.

The mechanical properties and thickness of adult temporal and occipital bones were examined in modern Japanese forensic samples. Cranial bones were obtained from 293 Japanese corpses (179 men and 114 women). During autopsy, left temporal (LT), right temporal (RT), and occipital (O) bone samples were extracted from each skull. Sample thickness (ST) was measured using multidetector computed tomographic imaging. The fracture load (FL) of each sample was measured by a bending test, in which the flexural strength (FS) was calculated. The FL and ST values for O were significantly greater compared with those of the LT and RT bones. The temporal bones were thinner compared with other parts of the skull and at greater risk for fracture. There is a need to take precautions to prevent temporal bone fractures. There were no significant differences in any of the values between LT and RT, indicating bilateral symmetry of the temporal bones. There were significant negative correlations between age and the FL and FS values for all sites in both sexes, except for O in the male samples, suggesting that older individuals are at increased risk for fractures. No significant correlations were observed between age and ST values in any of the samples. There were significantly positive correlations between FL and ST values at all sites regardless of sex.

In forensic medicine, hypothermia is a frequently encountered cause of death, and this characteristic provides public health information to prevent similar deaths in the future. Previous studies revealed regional differences in hypothermia occurrence (indoors or outdoors). However, to our knowledge, no recent studies in Japan have directly compared the characteristics of indoor- and outdoor-onset cases based on forensic autopsy reports. Hence, this study aimed to determine the characteristics and risks of unexpected hypothermia-related death. It included 218 cases from the Chiba Prefecture, Japan, wherein forensic autopsies were performed and hypothermia was diagnosed; these cases were categorized into indoor- and outdoor-onset cases, and their characteristics were examined. The results showed no significant differences between the two groups in relation to the age of onset or residential environment (i.e., the presence or absence of cohabitants). The outdoor-onset group tended to have a higher incidence of dementia. Regarding the causes of hypothermia, the indoor group had more internal causes (p < 0.0001), whereas the outdoor group had more primary and external causes (p < 0.0001 and p = 0.0029, respectively). The indoor group was more undressed than the outdoor group. Atypical antipsychotic components were predominantly detected in the blood in the outdoor group (p = 0.0077). The body mass index tended to be lower in the indoor group than in the outdoor group. Broadening public awareness of the present study findings may aid in developing preventative strategies for hypothermia based on the location of onset.