However, the death penalty was still "on the table", Mr Tuck said.
"Although the prosecution are now only seeking 18 years, in reality the death penalty is still very much on the table."
The prosecution argued British grandmother Lindsay Sandiford should only get 15 years in prison, but she was sentenced to death in Bali in 2013 after she was convicted of trafficking cocaine worth an estimated $3.2 million, Mr Tuck said.
"We will wait and see the decision and reasoning......then go from there. Hopefully he will be home in Wanganui at weeks end."
Throughout his trial at Denpasar court, the defence has argued de Malmanche had been effectively brainwashed by hours of online chat with someone identifying as 'Jessy Smith', whom he had fallen in love with.
They said the disability pensioner from Whanganui - who had a history of mental illness - was tricked into the Bali journey after developing an online dating relationship with her.
'Jessy' claimed to be a successful businesswoman and paid for his passport to travel to Hong Kong so they could meet.
It was the first time de Malmanche had travelled overseas.
After three days in Hong Kong, Jessy's assistant 'Larry' asked de Malmanche to buy a bus ticket to Guangzhou, where Jessie would meet him in a few days.
De Malmanche met Larry in Guangzhou, and after two days he was told Jessie was having visa problems and would now meet him in Bali.
They returned to Hong Kong, where Larry took him to a market to buy a bag for Jessie, which Larry put into de Malmanche's backpack.
He then flew to Bali, where he was stopped at the airport and detained by Customs for drug smuggling.
De Malmanche's trial began in February.
