William Rodney Swan, 31, and Thompson Kimura, 53, broke into Alexander Kormilets' Redfern apartment in the early hours of April 15 in 2013 and bashed and robbed the 78-year-old.

The attack left the elderly man with severe injuries to his brain, face, kidneys and chest and his mental condition became so poor he was unable to undertake or comprehend daily living activities.

After being in hospital for nearly four months, he was transferred to a high-level care facility and in December 2013 was found on the floor next to his bed moaning.

He was transferred to hospital where an X-ray showed he had fractured femur.

A decision was made not to operate and Mr Kormilets died in hospital a few days later.

A NSW Supreme Court jury in 2016 found Swan and Kimura guilty of murder.

Swan was jailed for a minimum 19 years and six months while Kimura was handed a slightly shorter sentence.

Swan unsuccessfully appealed to the NSW Court of Criminal Appeal which found there was sufficient evidence a decision not to treat Mr Kormilets' fractured femur was the result of the prior injuries sustained during the home invasion.

Swan then appealed that decision in the High Court which on Wednesday dismissed the appeal and upheld Swan's murder conviction.

Swan had challenged the ruling that the low quality of life Mr Kormilets suffered as a result of the assault substantially or significantly contributed to the decision not to operate on his femur which then resulted in his death.

In dismissing Swan's appeal, the High Court found the cognitive decline suffered by Mr Kormilets as a result of the assault led to his inability to communicate properly.

"The inference is irresistible that the decision was taken to treat palliatively rather than surgically based substantially or significantly upon the persistent, long-term, and catastrophic effects of the assault," the court said in its judgment.

Australian Associated Press