Sydney  - Sue Aldred knows the adrenalin rush when the sky is crimson, fireballs leap from tree to tree and it's either your house turned to ash or the narrowest of escapes.

"I did fear for my life at one point," said Aldred, who saved her house when fire rushed through her township of Kinglake on Saturday night. "All of a sudden, we were in a raging inferno, there was coloured smoke and the noise was indescribable."

This week 19-year-old former volunteer firefighter Jarrad Brewer will appear in court in Melbourne on charges of deliberately starting forest fires not far from Kinglake.

He's likely to be asked about the thrill of seeing flames four storeys high and battling to keep them at bay.

Over half of forest fires are the work of arsonists. Few are caught because it takes only a moment and a match to start a conflagration that can kill people, reduce forests to ash and blight thousands of lives.

"The deliberate lighting of bushfires is essentially an Australian phenomenon," said former justice minister Chris Ellison.

The motivation of arsonists is difficult to fathom precisely because so few are caught. The forensics are improving - police will allege that Brewer's fingerprints were on a fuel container found near a fire he himself reported - but it's a difficult crime to detect and prosecute.

Psychologist Rebekah Doley says arson is a simple crime but culprits are complex. "They also tend to be serial offenders and, in my experience, will not stop until caught," she said.

Forest fires to Melbourne's north are likely to have killed more than 40 people, razed hundreds of houses and been the death of tens of thousands of domesticated animals. But the televised carnage hasn't curbed the appetite for more arson.

Deputy fire chief Steve Warrington said arsonists were still at work - some relighting fires that 30,000 volunteer firefighters had risked their lives putting out.

One estimate is that 20 per cent of arson attacks are the work of firefighters. Dozens have been prosecuted in the past five years. Some had moved from state brigade to state brigade to avoid suspicion.

Ted Baillieu, leader of the opposition Liberal Party in Victoria, wants tougher sentencing and keener monitoring.

"We need a register of arsonists in this country and we need mandatory minimum sentences for people found to have deliberately lit bushfires," he said.

Damon Muller, the author of an Institute of Criminology report released last month, says that arsonists are likely to engage in other sorts of crime - and be poor, male and live in areas with low incomes and high unemployment.

Muller recommends that police focus their attention on these areas, especially those near national parks.

Muller praised fire brigades for rigorous testing of recruits to try and weed out firebugs. "Just as paedophiles will be attracted to work in child-care centres, people who are into fire will be attracted to working in the fire services," he said.

Recent deadly fires will generate more pressure for very tough measures. When the fire season comes round at the height of the southern hemisphere summer, police already keep watch over convicted arsonists or those who are suspected of being firebugs.

There are calls for convicted arsonists to be put in protective custody on weekends like the last one when roaring winds and intense heat combine to create conditions for the perfect firestorm.

Magistrate Tom Hassard, who will preside over Brewer's trial, was widely applauded last week when he denied bail and kept the former firefighter in custody over the weekend.

"The community interest must be dominant," Hassard said. "The activity of starting bushfires is at the apex of community concern and it's unfathomable as to why a person would be motivated to start such fires." (dpa)