In her closing address to a Supreme Court jury yesterday, Crown prosecutor Michele Williams, SC, said the three men had taken part in a joint criminal enterprise to kill Gordon Hamm.

"The motive was money, drugs. It was greed," Ms Williams said. "They were involved in the drug trade."

Mark Moreland, Christopher Tippins and Tai Thorp have pleaded not guilty to murdering Mr Hamm on July 17, 2013.

Mr Hamm, 34, from Mount Gambier, was believed to have been in Portland to buy drugs after earlier winning more than $5000 on the pokies.

The Crown case was that just before 4am on July 17, 2013, a four-wheel drive being driven by Mr Moreland approached a car in which Mr Hamm was a passenger on the bridge over the Glenelg River at Nelson, near the Victoria-South Australia border.

Another car, being driven by Mr Thorp, was then used to box Mr Hamm's car in.

Mr Moreland and Mr Tippins, who had been in Mr Thorp's car, then allegedly dragged Mr Hamm out of the trapped car.

"It was the dead of night on a bridge with no escape and the inference, we say, is that they knew (Mr Hamm) had gone to Portland to 'reload', that is, to get more drugs. They were part of the drug trade, that's what they wanted, all three, and (Mr Hamm) was cashed up.

"There is communication between all three ... leading up to the events, meaning they were planning it together and they lay in wait for him."

Mr Hamm was repeatedly bashed with a rifle butt and was on his hands and knees when Mr Tippins told Mr Hamm's driver to "get out of here". The driver claimed Mr Hamm was "squealing like a pig" at the time.

Ms Williams said the fact Mr Hamm was shot and bashed and pursued when he tried to get away down an embankment showed what was on the minds of the three accused men.

The prosecutor said Mr Hamm's screams stopped or trailed off after he had been bundled into a car and the three men immediately drove off to get rid of the body.

"So, they race off in the two cars towards the pine plantation, immediately, we say, and there mightn't have been much blood at the scene, but it doesn't take much blood sometimes to kill someone either."

Mr Hamm's body has never been found.

Barrister Theo Kassimatis said Mr Moreland was part of the ambush but he was not a party to any agreement to kill Mr Hamm.

"There is no evidence that anyone was shot. There is evidence that a shot was fired. That's it," he said.

"(Mr Hamm) is supposed to have been shot on that bridge, and there is a few droplets of blood. Where's the blood - where is the blood consistent with murderous intent?"

The trial, before Justice Michael Croucher, continues.