The role of mental illness in homicide-suicide in New Zealand, 1991 - 2000.

Prior studies of homicide-suicide (H-S) have largely glossed over the relevance of mental illness (MI), either ignoring the issue outright or defining H-S cases as intrinsically related to MI or not. While such positions have methodological or theoretical justifications, it was felt that a finer-grained analysis was possible and might prove fruitful. As part of a large population study on homicide and MI in New Zealand, all H-S cases over a 10-year period were identified through a police database and their Coronial Services files reviewed. Thirty-three H-S cases (0.08 per 100,000 prevalence) were identified. Fourteen perpetrators (42.4%) were classified as MI; among these were all five of the female perpetrators and 32% of the male; 20% had not previously been in treatment. Most of the MI perpetrators killed their children and then themselves. In contrast, only a few of the H-S perpetrators who killed a current or former partner were MI. It is concluded that H-S events in New Zealand appear broadly similar to such events in other countries, and that MI plays a significant role in some forms of H-S. However, the relationship between gender, H-S motivation, and mental illness is clearly complex and in need of further study.