Brendan James Sokaluk, 42, is alleged to have deliberately started the fire near Churchill, in Victoria's east, which destroyed more than 150 houses and killed 10 people on February 7, 2009.
Sokaluk's car broke down on a road next to where the fire allegedly started, the Victorian Supreme Court heard on Monday.
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Prosecutor Ray Elston SC said investigations showed there were two points of ignition for the blaze.
Sokaluk had told police he accidentally started it by throwing a burning piece of paper from his car, which had caught alight after he dropped a cigarette inside the vehicle, the court heard.
Sokaluk had also said he was upset by the fire because he had caused it, Mr Elston said.
Sokaluk had claimed he was in the area because he was attending a wedding, but had also told people he was visiting a friend.
Mr Elston said Sokaluk had told lies and had no legitimate reason to be in the area that day.
A few days after the blaze, Sokaluk called Crime Stoppers to report that he saw a Department of Sustainability and Environment firefighter light the fire.
Sokaluk's barrister Jane Dixon SC said it was natural for people to want to blame someone for the fire and her client was an easy target.
She said he had even made himself believe that he started the fire.
Ms Dixon said a defence expert would say there were no telltale signs the fire was deliberately lit and that there were a number of possible causes for the blaze including rubbish spontaneously combusting in the hot weather.
"The question for you is,'Was this a case of arson at all?'," Ms Dixon said.
She said her client has autism.
Sokaluk allegedly watched the fire from the roof of his house.
The fire began at about 1.30pm in a bluegum plantation near Churchill in 44-degree conditions and on a day of total fire ban.
Fanned by winds at times gusting to over 60km/h, it spread quickly.
Mr Elston said the wind changed about 6pm and the fire hit several towns, killing 10 people.
Sokaluk, who was a CFA volunteer from 1987 to 1988, has pleaded not guilty to 10 counts of arson causing death.
The trial before Justice Paul Coghlan is continuing.
