Mr Suhadi said Mr Roberts had "contradicted the Indonesian government's program to eradicate narcotics and illegal drugs" and his actions had "ruined his own health".

But the mitigating factors in Mr Roberts' case, Mr Suhadi said, included the fact that he was "honest and admitted fully what he did during the trial".

"The defendant has never been convicted and has promised to undergo therapy for his narcotics addiction," Mr Suhadi said.

In addition, assessments by Indonesian and Australian doctors found Mr Roberts was an addict and that he had been a user of multiple narcotics, including ice, methamphetamine, cocaine, ecstasy and marijuana since the year 2000.

When admitted to Bhayangkara hospital, he had been diagnosed with mental health and behavioral issues due to the methamphetamines, as well as depression and anxiety disorders.

Mr Roberts sat emotionless during the proceedings in the court on Thursday and did not speak afterwards.

In February, Mr Roberts said that he was in rehabilitation and that he had been clean for 10 weeks.

"Given that I am in rehabilitation and I have the support of the authorities, I suspect [the death penalty] is not likely," he told reporters at the time.

His legal team has emphasised his history as a drug user with a history of depression, past trauma and suicidal tendencies.

Chief judge I.G.N.Putra Atmaja adjourned the trial to April 4, when lawyers for Mr Roberts will present their defence.