The trial of a man accused of murdering a woman and her son more than four decades ago has heard he told a car dealership that he had burned part of his car’s boot.

William MacDowell, 80, denies murdering his son, Andrew MacRae, three, and the child’s 36-year-old mother, Renee MacRae, on November 12 1976.

He is also accused of disposing of their bodies and also disposing a boot hatch from a Volvo car to defeat the ends of justice.

On Wednesday, the High Court at Inverness heard from Ian Cattanach, who worked for Volvo dealership Autosales at the time of the alleged incident, who told defence KC Alex Prentice that MacDowell had wanted a replacement floor for the cargo area.

“The floor was removed. I asked him where the floor was, he said that he burnt it,” the 76-year-old told the court.

“He said he was building a house and throwing building material in the back had ruined the floor.”

Mr Cattanach told the jury that he “couldn’t understand” why he wanted it the same day, and that he told MacDowell him they didn’t have the parts which would take a month to arrive.

The car dealer told the court that MacDowell later came back in “a better frame of mind” and they did the work for him, removing the part from another vehicle in stock to fit onto his as he was a good customer.

Giving evidence earlier, MacDowell’s wife, Rosemary, told the court that the accused’s poor health meant he is a “walking dead man”.

The 80-year-old told MacDowell’s defence lawyer, Murray Macara KC, about her husband’s health, including his poor mobility and the medication he is on.

“He has a very sick liver, very sick kidneys and his heart is trying very hard to keep him alive,” she said.

“He’s actually a walking dead man, and he has a DNR (do not resuscitate) set up already.”

MacDowell denies all three charges and has lodged a special defence of incrimination and alibi.

Retired officer Peter Black, now 80, told the court of an “agitated” and “volatile” interview in the 1980s after Mrs MacDowell was detained at the couple’s former coaching house, the Crook Inn in Peeblesshire, and taken to the police station in Peebles.

During the interview, he challenged discrepancies in her story as to when her husband arrived home, which she said was about 8.30pm. She said: “Well, that must have been right at the time. I didn’t cover up anything.”

And, the court heard, when told that television programme The Quest finished after 10pm, and this did not fit with the 8.30pm arrival, Mrs MacDowell did not have an explanation.

In the interview, Mrs MacDowell told the officer: “I don’t know what you are getting on at me for. I never stabbed her or whatever happened to her.”

Christine Tuach, 81, told Mr Prentice that she had known the accused from school and that her husband John later worked at the MacRae factory as a manager.

On the evening that Mrs MacRae went missing, she told the court, she had seen a Volvo which looked similar to MacDowell’s company car on the A9. Inside, she saw a white man with heavy-framed glasses.

“I thought it was Mr MacDowell,” she said. “If it wasn’t him, it was somebody who looked like him.”

The trial, before Lord Armstrong, continues.