Frank Harton had pleaded not guilty in the South Australian Supreme Court to the attempted murder of 47-year-old Christopher Harton in February last year.

It had been alleged that Harton shot his mentally disabled son in the face at close range while they were on holiday on the River Murray, east of Adelaide.

Harton had feared he was dying at the time and was concerned that there would be no one left to care for his son after he was gone, the court was told.

After receiving several psychiatric reports and taking evidence earlier this week, the court yesterday concluded that Harton was not competent to stand trial over the incident and declared him not guilty by way of mental incompetence.

It must now decide whether to keep him in custody at a secure mental health facility or release him into the community under supervision.