Study looks at link to illness

Four out of five female killers and one in three male killers in Victoria had a mental disorder, research shows.

The unpublished study of homicide and mental illness, reported by the Melbourne Age, is part of a doctoral degree by a detective, Senior Sergeant Debra Bennett, and covered 380 men and 55 women who committed homicides in the state from 1997 to 2005.

The most common disorder was schizophrenia, which affected 38 of the 435 killers. Men with schizophrenia were eight times more likely to kill than non-schizophrenics, and women were 29 times more likely.

The study said the "vast majority" of schizophrenics were not a risk to others but sufferers were more likely than other killers to plan their actions and be motivated by revenge.