A bystander who suffered significant injuries when police knocked her to the ground at a Sydney Invasion Day rally has won $800,000 in damages after a judge found the officer breached his duty of care.
Lauren Cullen developed retrograde amnesia after her head struck the ground during the protest at Broadway in the city's CBD, leaving her with no memory of the incident.
NSW Supreme Court Justice Michael Elkaim ordered the state of NSW to pay the Irish national the damages in a judgment published on Thursday.
He found police were negligent when attempting to apprehend a protester, amounting to "a reckless exercise of the power of arrest".
The January 2017 incident kicked off after police saw a man preparing to light an Australian flag on fire and rushed forward to stop him.
Hayden Williams, a protester in the crowd, saw a police officer filming the unfolding events with a handheld camera and knocked it out of her hand, causing Sergeant Damian Livermore to rush over in an attempt to arrest Mx Williams.
In doing so, officer and protester were sent tumbling through the air, knocking the bystanding Ms Cullen to the ground.
The judge found the actions of police were causally responsible for Ms Cullen's injury as their decision to rush the man with the flag was the catalyst for the subsequent panic.
"The officers initiated a domino effect, culminating in the injury to the plaintiff," Justice Elkaim said
As police are only entitled to use such force as is "reasonably necessary", the judge found Sgt Livermore had a duty of care to not use excessive force.
Video footage of the incident was enough to find police actions were "reckless and out of proportion" to the danger posed and to the risk of injuring members of the crowd through the panic and confusion likely to ensue, Justice Elkaim found.
"I think the conclusion that the officers acted recklessly or unreasonably ... is easily reached," he said.
"Thus far I have found that the officers owed the plaintiff a duty of care, that the duty was breached, and the breach caused the injury to the plaintiff."
The judge did find that the arrest of Mx Williams was lawful as Sgt Livermore suspected on reasonable grounds that they had committed an offence, negating allegations of assault and battery.
The state was ordered to pay Ms Cullen's legal costs, subject to further order.