A judge has overturned a jail sentence handed to a climate change activist who blocked a lane of traffic on the Sydney Harbour Bridge. 

Deanna "Violet" Coco was last year handed a 15-month sentence with a non-parole period of eight months by a magistrate in the Local Court.

In April, Ms Coco and fellow activist Alan Russell Glover climbed onto the roof of a small truck parked in the southbound Cahill Expressway lane of the bridge during peak hour.

The pair lit a flare as they live-streamed the stunt, which lasted about 30 minutes and was part of action by the group Fireproof Australia.

The 32-year-old pleaded guilty to charges including disrupting vehicles on the Sydney Harbour Bridge, possessing a distress signal in a public place, using an authorised explosive not as prescribed, and resisting or hindering a police officer.

Mr Glover, a volunteer firefighter with the Rural Fire Service, was last week convicted and handed an 18-month community corrections order with a $3,000 fine, after also pleading guilty to one charge.

During an appeal hearing in Sydney's Downing Centre District Court, the prosecutor today said the incident caused "Massive inconvenience" and there were no extenuating circumstances to necessitate or rationalise it.

"This was not, on that day, an emergency," the Crown Prosecutor said.

"This was not a dire and unavoidable set of circumstances."

The court was played a short video showing helicopter shots of the bridge and the Crown argued at least three lanes of traffic were affected.

"The evidence doesn't show that at all," Judge Mark Williams said, after also commenting that it appeared like a normal morning.

'Overt and deliberate disruption of the peace in Sydney':

The prosecutor said the incident was not a peaceful protest, but "An overt and deliberate disruption of the peace in Sydney that morning with the normal flow of traffic on a main arterial road, during peak hour, brought to a standstill".

Judge Williams rejected the Crown's suggestion Ms Coco was a "Danger to the community" and had "No insight into her offending".

He set aside the jail sentence and placed Ms Coco on a 12-month conditional release order.

Convictions for two of her three charges will remain, while the charge of possessing a distress signal was withdrawn.

Mr Glover, who has been a firefighter for some 40 years and was at risk of being terminated due to his conviction, was also placed on a 12-month conditional release order and his conviction was set aside.

The court heard Ms Coco was sentenced on a "False factual basis" after a set of police facts claimed an ambulance under lights and sirens was prevented from attending an emergency due to the incident.

But that claim has since been retracted and Judge Williams asked how it found its way into the matter.

"That's something the police will have to answer to," Ms Coco's lawyer, Michael Blair, said.

The court heard Ms Coco had engaged in nine separate incidents of similar offending across three states in the two years leading up to the bridge protest and the Crown argued her behaviour had "Escalated in extremity".

But Mr Blair said her history was being "Blown out of proportion" and there could be no doubt she was motivated by genuine beliefs about climate change.

Original Story By | Jamie McKinnell