Custody issues are not the main reason estranged fathers kill their children.
They kill to punish their wives for leaving them.
'Please God not again'
A mother whose two children were murdered by their father seven years ago says she 'can't believe this keeps happening'.
Obsessive love lost: why some fathers kill
That is the conclusion of Australia's foremost expert on murder-suicide, Carolyn Johnson of Curtin University.
''Of the cases I studied, all the men had access to their kids and they used the access time to murder them,'' said Dr Johnson, whose book Come with Daddy, explored murder-suicides after marital separation.
A police hunt for five-year-old Kyla Rogers ended on Monday night near Casino with the discovery of her body in a car beside that of her father, Paul.
Earlier, the bodies of his former partner, Tania Simpson, and a ''family friend'', Anthony Way, were found in a flat on the Gold Coast.
Dr Johnson said the kind of men who kill in these situations are those with a proprietorial attitude towards women and children.
They will not relinquish control, they are used to calling the shots in the family, and are often pathologically jealous. When they finally realise their wives are not coming back, they turn lethal.
''Homicide-suicide is their final act of control,'' she said. ''Very often they let their wives survive to experience the extreme pain of losing their children.''
Several recent high-profile cases have thrown the spotlight on estranged fathers who have resorted to murder.
Last month, Arthur Freeman was jailed for 30 years for throwing his daughter Darcey, 4, to her death off the West Gate Bridge in Melbourne.
The judge concluded he had used his daughter in an attempt to hurt his former wife ''as profoundly as possible''.
And last year another estranged father, Robert Farquharson, was jailed for a minimum of 33 years for deliberately driving his car into a dam and drowning his three sons near Geelong.
The judge said Farquharson had resented that his estranged wife had started a new relationship.
He has lodged an appeal.
Lesley Laing, a leading expert on family violence from Sydney University, said a history of controlling and violent behaviour was behind most cases of family homicide but too many people ignored or dismissed women's fears.
Her husband, Phithak ''Neung'' Kongsom, had been violent, controlling and she had taken out an apprehended violence order, but she did not think he would ever kill the children.
Yesterday she said women had to be ''hyper-alert'' to signs that men were putting the children's welfare at risk.
Several recent cases have thrown the spotlight on estranged partners who resort to drastic acts of revenge, writes Adele Horin.
