A Perth man has been remanded to a maximum-security psychiatric ward after being charged with his mother's murder.

Police allege Samuel Ashby attacked his 68-year-old mother, Deann, in her home at Mosman Park, in the city's west, on Sunday night.

Major Crime Squad detectives charged the 39-year-old Wembley man with murder on Monday.

Defence lawyer Bill Harris said his client needed treatment for mental illness.

"He's just not very well," Mr Harris told reporters outside court.

Mr Ashby has been referred to the Frankland Centre at Graylands Hospital and is expected to appear in the Perth Magistrates Court on June 10.

AAP