Shalvin Prasad's fiery death was likely to have been carefully planned by a killer who wanted to leave no evidence behind, says an expert in clinical psychology.

The 21-year-old supermarket worker was alive when he was set alight on January 31 and police believe his death could be linked to the sudden withdrawal from the bank of tens of thousands of dollars he had saved.

Dr Ian Lambie, associate professor of clinical psychology at the University of Auckland, said the manner of death was cruel and unusual - and premeditated.

Although he was unable to comment specifically on the case, he told the Herald many murders were the result of a random action like a fight.


However, in this case it appeared someone took Mr Prasad to McRobbie Rd in Kingseat, south of urban Auckland, knowing exactly what they were going to do.

"In situations like this it's quite different [from a random act]. There was sufficient accelerant [to kill] - you know what the outcome will be. For whatever reason, that's what they decided to do."

A fire often left no evidence trail because many clues were destroyed. "Unless they leave footprints around the site it makes it hard for the police to determine who did what when, and that's the challenge of it."

Professor Lambie believed police were right to keep an open mind as to the motive, but on the face of it the money seemed crucial.

"You have to know the motive for the crime but you obviously have to look at the amount of money he took out prior to that."

His view was that any crime where the victim was made to suffer set it aside from other violent acts.

"I think any sort of crime where a person is killed is horrendous [but] I think a killing when a victim suffers after some period [of] time is absolutely horrendous. They are all awful but that takes it into another category as well."

Asked about the psychology of anyone doing such an act, Professor Lambie said it was cold, hard and callous.

"It allows them to step over the line and not actually have any empathy and any sort of feeling for the impact on the victim."

Despite popular belief that anyone who committed such a crime would be in the grip of psychosis, Professor Lambie said the person, or persons, would not necessarily display those traits.

But it would be a very difficult secret to keep.

"It would be unusual to do something like this and [it] not have some effect on them at least internally. Their physical appearance [may] not change but there might be some psychological effect on them about the way they committed this."

Police have been speaking to criminal profilers to see if there is any link between the way Mr Prasad was killed and the motive.