Aussie bomb-maker appears in court

A man who said a bomb he built would "make a big bang" should have known it had the potential to seriously injure, a court has been told.

Prominent animal research scientist Lionel Barry Lowe, known as Barry, was killed in an explosion just after going out to mow the lawn at his property at Dural, in Sydney's northwest, in May last year.

Police initially thought the 67-year-old's ride-on lawnmower had blown up, but later said a home-made bomb found in a skip on the property was the source of the blast.

Ashley Glenn Wright, a friend of Barry's son Jonathan Burton Lowe, has been charged with manslaughter after admitting he built the improvised explosive device that killed the father of five.

On the first day of his trial in the Downing Centre District Court in Sydney on Monday, crown prosecutor Craig Emerson said Wright and Jonathan Lowe had built the bomb "on commission" for a third party and had been paid A$3000 (NZ$3826) for it.

Wright had told police he hadn't built the bomb with the intention of hurting anyone, but that he knew it would "make a pretty big bang", Mr Emerson said.

When the man to whom the pair had sold the bomb returned it, it was discovered by Barry.

"What happened after that was not all that clear - it seems that Barry Lowe took it with a view to in some way getting rid of it," Mr Emerson said in his opening address.

He said that even if ultimately Barry Lowe's actions in trying to dispose of the bomb were the cause of his death, the very act of making the bomb was manslaughter.

"The crown is setting out to prove that the making of the improvised explosive device was unlawful," he said.

"A reasonable person in the position of Ashley Glenn Wright would have realised that by that act other persons, including the deceased, were being exposed to an appreciable risk of serious injury."

Jonathan Lowe and his mother Diana Lowe, Barry's wife, are expected to give evidence against Wright on Tuesday.

- AAP