Officials who helped rescue a little boy from his pedophile parents have given an in-depth account of how they cracked the case.

A little boy adopted by a pedophilic Queensland couple and farmed out to an international ring of sex abusers was rescued thanks to a distinctive temporary tattoo, investigators have revealed.

Australian, New Zealand and US officials have given an in-depth account of how they brought down the two men in a Four Corners report.

Peter Truong and Mark Newton paid US$8000 for a child, adopted him, then took him on a world tour of abuse.

The report revealed the pair trained their young son not to give information to investigators by staging mock interviews.

Detective Inspector Jon Rouse from Queensland Police said the boy “withdrew completely” during police interviews.

“You know, he would hide, he wouldn’t look at the interviewer,” Det Insp Rouse told the ABC program.

“I believe one of his responses was that he didn’t want to get them into trouble.”

Images found on a hard drive in the Truong-Newton home showed the boy had been taken to 30 countries in six years, meeting unidentified men.

The young boy – named as Adam in the Four Corners report – had filled his passport by the age of three.

And it was an overseas holiday snap that helped detectives close in on his adoptive fathers.

Photos dated April 2011 showed him getting a henna tattoo at a zoo in North Carolina.

Det Insp Rouse said the tattoo proved crucial in helping identify Adam.

“The dead set immediate giveaway was the tattoo,” he said.

“There’s a henna tattoo, very, very particular.

“You put it all together, it’s definitely our boy … that was it, case closed.”

Newton was sentenced to 40 years’ jail last year, while Truong received a discount for supplying passwords to encrypted hard drives, thus helping secure the arrest of other international pedophiles, and was jailed for 30 years.

The Four Corners program comes with high-profile Florida lawyer John Rex Powell agreeing to serve at least 20 years’ jail in the US for his involvement in the ring.

In a deal with prosecutors in Indiana, Powell agreed on Monday to serve up to 30 years behind bars, and after his release be subject to supervision for the rest of his life.

An Indiana judge will decide how much time he will serve.