A man has confessed to murdering a Melbourne woman found bleeding to death by her 11-year-old twin daughters six years ago, and to an attack which broke the spine of a 73-year-old widow months earlier.

Scott Alan Murdoch, 41, pleaded guilty on Thursday to murdering Kylie Blackwood and intentionally causing serious injury to Ilona Prohaska during robberies.

His confessions came as the supreme court prepared to assemble a jury for his criminal trial.

In May 2013, Murdoch broke into Prohaska’s home, knocking the 73-year-old to the ground, cutting her throat, breaking her spine and shoulder and stealing $70 cash and a debit card.

In August the same year, Murdoch struck again, stabbing Blackwood, 42, repeatedly and leaving her with multiple wounds to her neck and chest. She was discovered bleeding to death on a couch by her 11-year-old twin daughters.

Murdoch had previously denied the murder.

But he pleaded guilty at the last chance and also confessed to the attack on Prohaska after the latter charge was downgraded from attempted murder.

Advances in technology helped police pin Murdoch to his crimes years later when he was identified as a strong potential match to DNA found on Blackwood’s jeans and Prohaska’s jumper.

Blackwood was unresponsive when discovered by her daughters, who had walked home from school after their mother failed to collect them.

Prohaska, a widow originally from Hungary, had opened her door to Murdoch, believing he was a tradesman she had been expecting.

She later told police he used a hammer to pound a knife into each side of her neck as she screamed for help.

Murdoch faced court dressed in a cotton T-shirt, jeans and sneakers. He is due to appear before Justice Jane Dixon again on 16 August for a further mention before sentencing.