Cy Walsh pleads not guilty to murdering father Phil Walsh.

Cy Walsh has pleaded not guilty by reason of mental incompetence to murdering his father, former Adelaide Crows coach Phil Walsh.

The 55-year-old died from multiple stab wounds at his Somerton Park home in July.

His wife, Meredith, was also taken to hospital and treated for a leg injury.

Their 26-year-old son was charged with murder and has been detained at the secure psychiatric facility James Nash House.

Walsh today appeared in Adelaide Magistrates Court through a video link and entered his plea through his lawyer.

Walsh did not speak during the hearing.

He was dressed in a green tracksuit, was clean shaven and his hair had been cut short and was slicked back.

He will now face the Supreme Court in February.

This post originally appeared on ABC News.