Accused 'baited' SA murder victim: court

An Adelaide man was lured into a car by his ex-girlfriend before being fatally shot by her new partner, who was hiding in the boot, a jury has been told.

Jason Bucca, 25, and Tristan Kaye Castle, 37, have denied murdering 39-year-old Adrian Paul MacDonald, from Hope Valley, at the Big Bucket Car Wash in Parafield on the morning of February 3, 2013.

In the Supreme Court of South Australia on Friday, Crown Prosecutor Jim Pearce SC said Mr MacDonald was unaware that Bucca was lying in wait with a gun when Castle enticed him into the front passenger seat.

Mr MacDonald was shot in the hip before a close-range "coup de grace" was fired into his head while he was on his knees or lying down, Mr Pearce said.

His injuries were consistent with him having been shot from the boot of the car or the back seat, while trying to escape from the car, the prosecutor said.

Mr Pearce said Castle persuaded Mr MacDonald to meet with her at the car wash under the pretext of discussing their relationship, which had ended acrimoniously.

He said text messages between the pair earlier that morning showed Mr MacDonald was suspicious about Castle's motives for wanting to meet with him.

"How can I trust you're not setting me up?," Mr MacDonald wrote in one text.

"I wouldn't do that," Castle replied.

CCTV footage showed a silver Ford Futura at the car wash at the time of the crime, which Mr Pearce said was indistinguishable from a car owned by Castle's mother.

Text messages showed Castle had arranged to borrow the car from her mother in the hours before the shooting, Mr Pearce said.

The car was seized by police after the shooting, and a forensic examination revealed traces of lead, barium and antimony, which Mr Pearce said was consistent with gunshot residue.

Traces of gunshot residue were also found on Castle's clothing, he said.

The court heard Bucca had accused MacDonald of theft, calling him a "dog" in a text message.

The trial continues.