Women are more likely than men to plan the murder of a partner before they act, a university study suggests.

Griffith University's Australian Homicide Project interviewed 211 killers from Queensland, NSW and Western Australia to find out why they committed the crime.

Professor Paul Mazerolle says one of the study's aims is to understand why people kill their partners.

Of the 55 people interviewed who had killed their spouses, only about one in seven were women, he said.

But about half of those women had plotted their partner's murder.

He said only a quarter of the men had intended to kill.

Often, they had intended only to hurt their spouse but went too far.

Prof Mazerolle says men are more likely to lash out after feeling helpless in a relationship.

Getting sacked from a job, alcohol and drug abuse, suspecting a partner of cheating, or a partner threatening to leave could all contribute to such feelings, he says.

"When men are under those strains, it sets a context that makes violent incidents more likely to occur," Prof Mazerolle told AAP.

He said understanding why people killed their partners was important so support agencies could help before a death occurred.

Most of the inmates in the study were happy to share their story, he said.

"Many of them have said the main reason they want to speak is they hope it helps somebody else in the future," he said.

The findings were presented at a symposium in Brisbane today.