A 130-kilogram teenager who allegedly stomped a diminutive 64-year-old woman to death in her western Sydney driveway dealt the fatal blows because "God" told him to, court documents suggest.
Imanueli Jone Degei - who would later allegedly tell police he was on a "bad high" at the time - had been discharged from a mental health facility two weeks earlier.
Court documents detail how Zivan Gajic watched from the driveway of the Carramar unit he shared with flatmate Kristina Kalnic as then 18-year-old Degei staggered down the street in an apparent stupor on August 25.
Degei appeared to have passed out in a flower bed when Mr Gajic called Ms Kalnic to come and see if the young man was OK about 1pm.
Degei had taken off his shoes when the 40-kilogram Ms Kalnic followed him down the driveway.
Witnesses have said that, without warning, Degei lashed out once, punching Ms Kalnic in the head causing her to drop to the ground.
"I got out of the car and started screaming 'No, no, no don't, please don't do it'," a witness said according to the court documents.
But Degei allegedly stomped on Ms Kalnic's head three times. She did not survive her "massive head injuries".
Degei was arrested at the scene and allegedly told police he had not taken his medication that day but had smoked two "cones" of cannabis and was on a "bad high".
"The suspect also informed the custody sergeant he had taken some drugs that day as well as 'Jesus'," police documents state.
Degei told investigators he attacked Ms Kalnic "because God told me to ... because she had killed her husband".
The documents state the now 19-year-old is a diagnosed schizophrenic, who was discharged from Birunji Mental Health Facility on August 8.
Degei's matter is due back in Fairfield Local Court on Tuesday for a forensic procedure application.
Defence lawyer Omar Juweinat wants the court to understand many lives were affected by the "tragic events" including Degei's.
"There should have been serious reservations about his fitness to be discharged from a mental hospital in light of what occurred days later," the lawyer told AAP.
"Many lives have been affected by these tragic events."
