A MAN was shot dead and then his body burned and dissolved in acid because his killer feared he might "dob him in'' over a hydroponic cannabis operation, a jury heard today.

Prosecutor Mark Gibson said Leonard Borg took his victim, Peter Rule, to a factory in the Melbourne suburb of Campbellfield and shot him with a .22 semi-automatic rifle.

Mr Gibson said Mr Borg then phoned another man, who was involved in the cannabis business, and told him to buy bottles of bleach and plastic bags and bring them to the factory.

Mr Rule's body was placed in the back of Mr Borg's Volvo and when the other man arrived he was asked by the accused to clean up blood spatter in an area near some toilets.

Mr Gibson said that despite the clean up efforts forensic officers later found a blood spatter particle, and DNA testing determined it was 1.5 billion times more likely to come from Mr Rule than any other Caucasian person.

Mr Gibson said Mr Rule's body was taken to another factory in Thomastown, where Mr Borg and the other man had a cannabis crop, and there the deceased was placed in a 44 gallon drum and burned.

Mr Rule's body parts were placed in a plastic tub and dissolved in hydrochloric acid before Mr Borg and the other man took them to the Great Ocean Rd and disposed of the remains.

"The Crown says this was a calculated, planned and deliberate killing of Mr Rule in order to protect a cannabis growing business,'' Mr Gibson said.

Mr Borg, 28, of Mickleham, has pleaded not guilty in the Supreme Court to a count of murdering Mr Rule, 56, of Meadow Heights, on November 15, 2009.

Mr Gibson said Mr Borg lived in a house in Craigieburn where he grew cannabis and believed his Mr Rule was behind a police raid in August 2009 after a call was made to Crime Stoppers.

Mr Gibson said in April 2009 Mr Borg had rented the factory in Thomastown and started a hydroponic cannabis business with his younger partner who had borrowed $35,000 to help get it established.

The prosecutor said Mr Borg's belief that Mr Rule was an informer meant he was faced with the fear he would dob him in again over the Thomastown operation.

Mr Borg discussed his dilemma with another friend, Mr Gibson said, and told him: ''I've got to get rid of him to get peace of mind''.

The trial before Justice Lex Lasry is continuing.