Suicide and fatal single occupant motor vehicle collisions

Factors that influence choice of methods of suicide include availability of the material or device that is being used. Certain drivers utilise motor vehicles to deliberately self-harm, although ascertaining what percentage of these deaths were intentional is difficult. The files of Forensic Science South Australia in Adelaide, Australia were examined over a 5-year period from January 2005 to December 2009 for cases of fatal single occupant, single motor vehicle collisions involving impacts with trees, and for comparison, all cases of suicide. Tree impacts were selected as these represented the largest group of clearly defined single motor vehicle and solid object impacts. A total of 73 cases were identified, with those aged 1724 years accounting for the highest proportion of deaths, compared with suicide victims who were predominately aged 2539 years. Suicides showed little seasonal variation in incidence whereas more fatal collisions occurred in winter. A significant number of the drivers had ingested alcohol. The lack of a seasonal similarity in the occurrence of fatal collisions and suicides, and differences in the most common ages would be supportive of these groups being aetiologically different. Other factors in favour of these crashes not being intentional include intoxication and winter conditions.