Shane John Mason, 50, on Thursday again denied he was responsible for lighting two fires in Yarralumla in January 2014.

One was lit during a total fire ban and both prompted calls to triple-0 and the attendance of ACT firefighters and police.

Mason was homeless at the time, and was camping in bushland near the two fires.

He was found hiding in long grass and in possession of a lighter after the first, and laying in water near a bridge following the second.

Mason had sustained serious burns and was flown to hospital in Sydney for treatment.

His ACT Supreme Court trial neared a close on Thursday, but was adjourned until next month.

Mason claimed no knowledge of how either fire started, and denies lighting them.

He said he tried to put them both out after passers-by alerted him.

The court is also considering whether Mason, who has a lengthy history of mental health issues, was mentally impaired at the time and could not have known his actions were wrong.

The Crown continued its cross-examination of Mason on Thursday morning, and accused him of exaggerating his mental illness while talking to a psychiatrist to aid his defence.

Mason rejected that, saying, "If anything, I was under-emphasising it because I'm embarrassed and not proud of being unwell.

"I prefer not to talk about being unwell because it's very hard to get on with my life because of the crazy, stupid things that I've done."

He said he was very unwell at the time of the fires, but that it took six months of talking to friends and family before he realised.

The case will come back before Justice Hilary Penfold on November 5.