"Continue the holy struggle, get rid of Zionists, get rid of the Christian filth. God is great, this is my song," he sang, smiling broadly from behind a prison compound's bars.
It was not the first time Amrozi's behaviour had created surprise.
After his arrest in November 2002, his seeming good humour earned him the sobriquet of "the smiling bomber", as well as the vitriol of the press in Australia, where many of the Bali attack's victims lived.
And he surprised police by saying Americans were their intended victims, when Australians were far more likely visitors to the island.
Amrozi bin Nurhasyim was born in 1962 in the sleepy village of Tenggulun, a few miles inland from the coast of East Java, the fifth of 13 children.
Described as something of a black sheep, Amrozi did not do well at school, appearing more interested in motorbikes and girls.
The Bali blasts killed more than 200 people
Villagers in Tenggulun have said that Amrozi left for Malaysia in the late 1980s in search of work, and returned in 1991 with much stronger Islamic beliefs.
While in Malaysia, police said he was reunited with his elder brother, Mukhlas, a deeply religious man and also on trial for the Bali attack.
Amrozi has described Mukhlas as an inspiration to him.
Police said that when Mukhlas returned to Tenggulun, he became more involved in the village's Al Islam boarding school, founded by another of Amrozi's brothers, where about 150 students follow a strictly religious curriculum.
Amrozi is said to have admitted meeting the Muslim preacher Abu Bakar Ba'asyir on several occasions - while Mr Ba'asyir was in exile in Malaysia in the 1990s and more recently after the preacher's return in 1998, when he was invited to speak at the Al Islam school.
Mr Ba'asyir is thought to be the founder and spiritual leader of Jemaah Islamiah, a shadowy, regional network of militants thought to have carried out a number of attacks across South East Asia.
Amrozi angered families of the Bali bombing victims when he was paraded before the media in November waving and laughing, and was quoted as saying that he was "delighted" by the attack because they had destroyed "places of sin".
"With this incident, God willing, many people realised that they had forgotten God and neglected their worship and avoided places of worship," he said.
"Often things we don't like are in fact good for us," he added.
General I Made Mangku Pastika, chief of the investigation, said Amrozi showed no remorse for his involvement.
"He's very calm, very cool... proud of his activities," he said.
Mr Pastika said Amrozi's only regret about the bombing was the fact that most of the dead were Australians rather than Americans.
"He doesn't regret it but he is just unhappy," Mr Pastika added.