An Australian police officer has pleaded not guilty to manslaughter in a Sydney court - after accusations he tasered a 95-year-old woman

In May last year, Senior Constable Kristian White and his partner were called to a care home to reports an "aggressive" resident was raising a steak knife at staff.

It's alleged White tasered dementia patient Clare Nowland, after she didn't drop the knife.

She fell and fractured her skull - and died in hospital a week later.

The trial is expected to last three weeks.