The Department of Internal Affairs says the long prison sentence handed out to an Australian man for sexually abusing a young boy was the direct result of one of its staff noticing something suspicious about a series of photos.
The man has been jailed for 40 years in the United States after he and his male partner bought the newborn for $US8000 in an undisclosed country, abused him and then handed him off to other paedophiles to abuse.
Internal Affairs investigator, Jon Peacock, noticed something suspicious about a series of photos of a six-year-old boy stored on the computer of a New Zealand man in a separate investigation.
The images were of the boy with the man being investigated and two other adult men.
Mr Peacock said while there was nothing illegal about the photos, the way the boy looked into the camera was unusual.
He used car registration plate numbers from the photos to track the men to Queensland.
The 42-year-old man was arrested in California last year. The boy's other Australian guardian has entered a guilty plea and is awaiting sentencing and two other American men have been charged.
Police say the boy, now eight, had been living with the men in Cairns for several years when, in 2011, New Zealand authorities discovered that the child had been used in child pornography.
Queensland police raided the couple's house in 2011, just after the men and the boy had left for the United States, the ABC reports.
The 42-year-old was sentenced in the US District Court in Indianapolis on Friday.
Judge Sarah Evans Barker said he deserved a harsher punishment but accepted the plea deal because she did not want to subject jurors to the disturbing evidence.
Prosecutors discovered videos and photos of the man, his partner, also an Australian, and other men in Australia, the US, Germany and France abusing the child from the age of two to six, AAP reports.
"For more than one year and across three continents, these men submitted this young child to some of the most heinous acts of exploitation that this office has ever seen," Indiana US Attorney Joe Hogsett said after the sentencing.
The 40-year sentence was the maximum available for the conspiracy to sexually exploit a minor and conspiracy to possess child pornography charges the man entered guilty pleas to.
His partner has also entered guilty pleas and will be sentenced later this year.
The court heard the two men, who had been living in California, bought the newborn boy in an undisclosed country and used falsified documents in Los Angeles to claim legal guardianship.
The boy was rescued by US authorities and is being cared for in California.