The 49-year-old walked out of her home in Melbourne's north-west at around 10am after an argument with her husband over money.
The last thing Karen reportedly told her husband, Borse Ristevski, was "I’m going to go and clear my head."
Now police are investigating a new lead, following a witness telling detectives they saw a man standing alone with Karen's car in the Mt Macedon area - close to where her body was eventually found.
The significance of this sighting before the body was discovered “cannot be overstated”, a police statement said, according to News.com.au.
Police will today head to the area to continue to search for clues.
They will focus on roads the killer likely took both before dumping the body and upon leaving the area, the Herald Sun reports.
Though Mr Ristevski denys having any involvement in the disappearance of his wife, both his and Karen's phones “pinged” off transmission towers on the Calder Freeway on the day of her disappearance and Mr Ristevski's phone was then switched off for two hours.
This article first published on Marie Claire.