Professor Elder is an expert on children's sleep problems and a member of the Family Violence Death Review Committee.
She said sleep problems were very common in children and could be due to simply worrying about something they had read in a book, or about bullying at school.
"But of the children who have had violent experiences, it's very important to consider whether they are getting enough sleep."
She said sleep was often, but not always, considered when family violence was reported.
"In the group where someone is killed, not all children get medical attention," she said.
Dr Patrick Kelly, clinical director of the child abuse unit at Auckland's Starship hospital, said all siblings were assessed when family violence involving a child under 5 was reported to his unit before someone died. "But if they die and it goes to a pathologist, maybe not."
He said family violence was the single biggest factor accounting for rapidly increasing reports of emotional abuse of children. He called for all agencies to be open-minded in the way they worked together with children who had been abused or neglected and their families.
Dr Elder said 47 per cent of all New Zealand homicides from 2009 to 2012 were the result of family violence, and 111 children lived in a house where someone died of family violence in those years.
More than 500 social workers, health workers and educationists are attending the four-day Australasian Child Abuse and Neglect Conference, which is jointly sponsored by the Australian and New Zealand governments.