This paper describes a retrospective analysis dealing with the sudden natural or unnatural death of psychiatric patients using actual autopsy findings, clinical information and demographic status. More than 70% of the 141 patients had schizophrenia, mood disorders or substance-related disorders. Accidental deaths were the most common (34.8%) and followed by natural deaths (28.4%), suicide (22.7%) and homicide (9.2%). Nearly half of mentally retarded patients died natural deaths, whereas two-thirds of patients with substance-related disorders died accidental deaths and about one-third of patients with schizophrenia and mood disorders committed suicide. Furthermore, patients with substance-related disorders were significantly more likely to live alone than were patients with schizophrenia or mood disorders. Twenty-five cases died in hospitals or other healthcare facilities; it is noteworthy that in the 12 patients who died natural deaths the reported symptoms had been less severe than might be expected and correct clinical diagnosis was not made before death. The present findings should be useful for both forensic pathologists and clinical psychologists.

To clarify the characteristics of injuries of motorcyclists dying in accidents in relation to helmet type, we retrospectively analyzed forensic autopsies of 36 helmeted motorcycle riders. The presence of major injuries and injury severity were evaluated with the injury severity score and the 1990 revision of the Abbreviated Injury Scale. Persons with open-face helmets (19 cases) were significantly more likely to have sustained severe head and neck injuries, especially brain contusions, than were persons with full-face helmets (17 cases). Furthermore, major injuries of the chest or abdomen, rib fractures, lung injuries, and liver injuries were each present in more than one quarter of all cases (26.3% to 70.6%), but their prevalences did not differ significantly between riders with different types of helmet. Because many types of head and neck injuries cannot be prevented and fatal chest and abdominal injuries occur despite the use of full-face helmets, more effective helmets and devices for protecting the chest and abdomen are needed to decrease deaths from motorcycle accidents.

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Biomechanical analysis was performed to evaluate the effectiveness of mastering ukemi in preventing severe head injury in judo. One judo expert (tori) threw another judo expert (uke) with a skilled breakfall (ukemi) four times. We obtained kinematic data of uke with a digital video camera. Both translational and rotational accelerations were measured with a six-degree-of-freedom sensor affixed to uke's forehead. When Osoto-gari was performed, uke fell backward and his arm made contact with the tatami; the translational and rotational accelerations rose to peak values. The peak resultant translational and rotational accelerations were respectively 10.3 ± 1.6 G and 679.4 ± 173.6 rad/s 2 (mean ± standard deviation). Furthermore, when comparing the values obtained for the judo experts with those obtained using an anthropomorphic test device (ATD: the POLAR dummy) that did not perform ukemi, both the peak resultant translational (P = 0.021) and rotational (P = 0.021) accelerations of uke were significantly lower than those for the ATD, whose head struck the tatami. Additionally, there was no significant difference among the three axis directions for either translational (a x : 7.4 ± 0.2, a y : 8.5 ± 2.1, a z : 7.2 ± 0.8 G) or rotational (`x: 576.7 ± 132.7, `y: 401.0 ± 101.6, `z: 487.8 ± 66.6 rad/s 2 ) acceleration. We confirmed that performing correct ukemi prevented the elevation of head acceleration by avoiding head contact with the tatami when a judoka is thrown by Osoto-gari. Judoka should therefore undertake intensive practice after they have acquired ukemi skills.