An investigation into the Cairns couple - dubbed Operation Juliet Conduit - began after they claimed to have adopted a baby from a Russian surrogate mother.
Detective Inspector Jon Rouse of Taskforce Argos - a highly specialised branch of the Queensland Police responsible for investigating online child exploitation and abuse - said it soon emerged the pair were lying.
His team discovered that Truong and Newton had actually "procured the child for the intent of sexual exploitation and had facilitated the abuse of the child as part of an international network of child sex offenders".
Truong, 46, and Newton, 39, were arrested and charged during a trip to the United States in February 2012.
Both were convicted of conspiracy to sexually exploit a child and the sexual exploitation of a child.
Truong was sentenced to 30 years in a US prison and his partner was put away for 40 years.
"During the examination of devices belonging to the men, chat logs, images and video were obtained by investigators identifying the 42-year-old New Zealand man had engaged in the sexual abuse of the child and taken hundreds of indecent images," Rouse said today.
"This arrest closes the final chapter on a protracted and difficult investigation that has resulted in the arrest of members of a child sex offender network that spanned the globe.
"It is testimony to the dedication and commitment of Queensland Police child protection investigators."
Rouse and his task force worked closely with the New Zealand Department of Internal Affairs.
The Herald can reveal that a senior DIA investigator arrested the 42-year-old, and had been involved in the Operation Juliet Conduit from the beginning.
DIA spokesman Trevor Henry could not answer questions about the case while it was before the courts.
"As this is a Queensland Police investigation before the court we are unable to comment," he said.
A Queensland Police spokeswoman said no further arrests were likely.
"From a Queensland perspective, there are no further arrests expected and no other victims," she told the Herald.
"It is the closure of a very long investigation and this is the final piece."
