Phil Walsh and (inset) Cy Walsh.

The 27-year-old was previously found not guilty of murder because he was mentally incompetent when he fatally stabbed his father at the family home in Adelaide in July 2015.

In the Supreme Court on Tuesday, Justice Anne Bampton formally detained Walsh, who is subject to a supervision order for life.

The judge could have released Walsh on licence but after reviewing psychiatric and next-of-kin reports she accepted the request of prosecutors and detained him until further notice.

Walsh was suffering a psychotic episode as a result of undiagnosed schizophrenia when he stabbed the 55-year-old AFL coach 20 times, the Supreme Court ruled in September.

He heard voices he believed were from another dimension, and at times believed his father was the devil, court documents revealed.

His mother Meredith said she was left heartbroken but will continue to love and support her son.

THE CY WALSH CASE:

• July 3, 2015 — Cy Walsh stabs his father, Adelaide Crows coach Phil Walsh, to death on at their Adelaide beachside home

• Phil Walsh’s wife Meredith hospitalised with leg injuries

• A knife used in the attack is found at the scene

• Cy Walsh taken to Flinders Medical Centre for psychiatric assessment

• Held in custody at secure psychiatric facility James Nash House in Adelaide

• Extensive forensic, psychiatric and psychological reports presented to court as hearings continue through late 2015

• December 2015 — pleads not guilty due to mental incompetence in Adelaide Magistrates Court; committed to stand trial in Supreme Court

• August 2016 — prosecutors say they will accept Walsh was mentally incompetent at time of the killing

• September 28 — Supreme Court rules Walsh is not guilty of murder because of mental incompetence.

AAP