The only psychiatric witness in the case, Dr Jeremy O'Dea, has argued that the defendant was unlikely to have known his actions were wrong when he took three Molotov cocktails to the Brindabella Business Park last September.

Police confronted the man, and petrol from one of the Molotov cocktails spilled and caused an officer's leg to be engulfed in flames, leaving him with serious burns.

Another Molotov cocktail narrowly missed a police sergeant.

David Percival Burnett, 44, is currently facing trial on four charges, including recklessly inflicting grievous bodily harm, in the ACT Supreme Court.

Dr O'Dea, who has acted as both a forensic and treating psychiatrist for Burnett, diagnosed the man with a major depressive disorder, which was likely to have impaired him at the time of the offences.

The mental illness, he argued, would have meant he was unlikely to be able to control his actions or realise they were wrong.

The prosecution isdisputing those findings, arguing Burnett understood what he was doing.

Prosecutor Sam McLaughlin cross-examined the psychiatrist for several hours on Tuesday, culminating with an accusation that the doctor's close relationship with Burnett had "coloured" his evidence.

Mr McLaughlin put it to the doctor that his role as Burnett's treating psychiatrist made him closer to the defendant.

Dr O'Dea rejected that accusation, saying: "Yes, well I don't agree at all. Certainly that's not how I've conducted myself in this case."

Dr O'Dea noted other experts had agreed with his diagnosis.

Mr McLaughlin also questioned the psychiatrist about why he appeared to have deleted two paragraphs from one of his reports, that may have suggested Burnett was taking action to plan for his future, despite his diagnosed severe depression.

Dr O'Dea said he couldn't think why he would have done that deliberately, and or how such an action could help his client.

Acting Justice David Robinson has reserved his decision on the question of mental impairment and is expected to hand it down next month.

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