She arrived home at lunch with her groceries and a coffee and went into the family’s study to browse a cosmetics website.
Prosecutor Nick Papas, QC, told the court that a neighbour heard screams and disturbances in the house that tell a story of a confrontation that led from the study to the sunroom where Ms Blackwood was repeatedly stabbed in the neck and chest.
Her body was discovered by her then-11-year-old twins.
Murdoch left the house and went to a bank where he tried use her debit card but failed.
Mr Papas described Murdoch’s behaviour later as “extraordinarily cold” and “almost removes from any sense of what had happened”.
Three months later, Murdoch broke into Ms Prohaska’s Endeavour Hills home, knocking the 73-year-old to the ground and cutting her throat.
He took $70 and a debit card from her, forced her down a flight of stairs and hammered a knife into each side of her neck, causing significant blood loss.
Despite her severe and life-threatening injuries, Ms Prohaska was able to crawl to her medical alert button and call for help.
She recovered physically and celebrated her 80th birthday this week but was too traumatised to return to her home.
Murdoch withdrew $490 from Ms Prohaska’s bank account before going to an appointment with Corrections Victoria.
The hearing before Justice Jane Dixon is continuing.