Rosemary Davies was on her way to her regular cafe the Trading Post when she saw the "sporty" car at an intersection on Salisbury Road at Mount Macedon.

"It had no indicator on. It almost hesitated," she told Melbourne Magistrates Court on Wednesday.

"I'm thinking to myself, I wonder if they know where they're going."

Ms Davies, a journalist and landscaper, testified at a committal hearing for Borce Ristevski, who is accused of murdering his wife in June 2016.

Ms Ristevski was missing for eight months before her remains were found at Macedon Regional Park by two horticulturists in February 2017.

Ms Davies saw the black car at an intersection of a road leading to the park.

She said it wasn't tourist season so it was particularly quiet on the roads at that time.

She didn't think the Mercedes belonged to a local because it was so clean and urban-looking.

Ms Davies called Crime Stoppers in mid-2017, prompted by a story in the local paper about Ms Ristevski's death.

Detectives allege Borce drove his wife's black Mercedes-Benz roadster to dump her body, killing the signal on his mobile phone along the way.

The car plays an important part in the prosecution case as detectives allege it was also spotted by CCTV cameras in several places that day.

Mercedes-Benz expert Gordon Jones was called in to help identify cars in the footage.

"It has sports suspension," he told the court of the model. "It's as low as a car can be in this country."

Another witness, Glenn Golfis, said he spotted a black Mercedes stopped on the wrong side of the road in a grassy area at Mt Macedon around the same time.

"I don't know why it caught my eye, but it did," he said in a police statement, tendered to court.

"I thought to myself, 'What's going on here?'"

Ms Ristevski owned a dress store called Bella Bleu and one of her former employees also testified on Wednesday.

Diana Nastoska was working at the boutique the day her manager went missing.

When the always-punctual Karen didn't arrive to take over the store that afternoon she spoke to Borce.

"And he seemed surprised when you told him she wasn't there?" Borce's lawyer Sam Norton asked.

"Yes. He assumed she was already there. He wasn't sure what was gong on," Ms Nastoska replied.

The business was losing money at the time and the Ristevskis had significant loans and credit card debt, the court has been told.

Their daughter Sarah Ristevski said her mother sometimes became frustrated, letting it out by slamming the kitchen drawers and cleaning.

But she said her parents rarely argued and her father was never aggressive to her mother.

Borce claimed Karen walked out of the house to clear her mind the day she went missing and never returned, but police say he lied.

The committal hearing continues on Thursday.

Australian Associated Press