An expert witness called by Australia in its case against Japan at the International Court of Justice says he does not believe Japan's whaling program is for scientific purposes.

The hearing at The Hague is the latest step in years of attempts by governments and environmental groups to stop the Japanese whaling fleet's annual trips.

Professor Marc Mangel from the University of California, a specialist in applied mathematics and statistics, told the court that Japan's research programs - known as Jarpa 1 and 2 - have only considered lethal means to collect data.

"Lethal take can only make sense if we have a question that needs to be answered... a meaningful question," Professor Mangel said.

Australia is arguing Japan's practice of catching and killing nearly 1,000 whales a year for research disguises commercial whaling and contravenes international law.

Japan and Australia have both agreed to be bound by court's verdict and activists are hoping for a ruling against Tokyo that they believe will put an end to whaling in the Southern Ocean.

One of only a handful of countries that continues to hunt whales, Japan says the whales it kills each year contribute to research designed to establish if whale stocks are recovering from previous over-hunting.

The meat is eaten by the many Japanese consumers who consider it a delicacy.

Sorry, this video has expired Professor Marc Mangel delivers his testimony

Japan says its whaling is no threat to the survival of any species, but environmentalists and animal rights activists say whale hunting should be stopped completely.

Under a 1946 treaty on whaling, to which Japan is a signatory, countries can catch unlimited numbers of whales if they are needed for scientific purposes, regardless of the moratorium agreed in 1986.

The treaty does not address what counts as science, but lawyers for Australia said the collection of raw data without having in mind a specific question did not count.

"What you have before you is not a scientific research program. It is a heap of body parts taken from a pile of dead whales," said Phillippe Sands, a lawyer for Australia.

Japan will start presenting its case to judges on Tuesday.

ABC/Reuters