Remains found believed to be WA mum killer

The remains of missing killer Samuel Mark Walsh are believed to have been found inside a car in bushland in Western Australia's Goldfields region.

A Hyundai Excel hatchback was found in bushland near the Karalee Rocks Pumping Station, off Great Eastern Highway, in Yellowdine about 12.30pm on Wednesday.

Police say formal identification is yet to be made but the remains are believed to be those of 38-year-old Walsh, who was reported missing from a care facility in Claremont in 2014.

Walsh, who was also known as Enoch Samuel Walsh, was last seen in October 2014 when he failed to return from an authorised leave of absence from Perth psychiatric facility Romily House.

He had been found not guilty on grounds of insanity in March 2007 of murdering his mother at her Kalgoorlie home two years earlier.

The court heard Walsh hit his mother with a broadsword before slitting her throat with a bread knife and burying her in the backyard with his dog.

Walsh was ruled a chronically paranoid schizophrenic and not criminally responsible for his actions, and was held at a high-security psychiatric unit.

He had been granted regular leave since 2008 and had complied with supervised release conditions until failing to return in 2014.

Police say there is no evidence of criminality with the human remains and a report will be prepared for the coroner.