David Green, who was superintendent between 1968-70, told the commission: "I depended upon the trust, and trusted – had to trust – the integrity of the officers who were on duty at the time."

The commission has heard from four former inmates who were sexually abused at Turana. Two said they had been raped by officers.

Mr Green said he had been more concerned about boys engaging in sexual activity with each other, and assaulting other boys.

"On a hot, humid night in a secure section with boys or young men sleeping in confined quarters, the tensions and problems which would arise from that were complex and real, and that could not be denied," he said.

"I was focused on the child-to-child behaviour of boys or young men being locked together in different types of nightly sleeping arrangements. I tried to take some measures with respect to dealing with those situations. but some of them were impossible to deal with."

Mr Green said up to 11 officers were on duty at night to monitor boys in 12 sections, with about 16 or 17 boys in each section, a situation he described as "precarious".

A former employee of Turana told the commission that the Department of Health and Human Services had no policies to deal with the sexual abuse of children in its care.

The public gallery broke into spontaneous applause when an emotional Ashley Cadd said the department had failed in its duty of care to boys incarcerated at the now notorious youth correctional facility.

"They may have been offenders but they're human beings starting on the journey of life," he said.

"I'm near the end of mine, but so help me God I hope someone puts the proverbial rocket under the department and make them take responsibility for what they've undertaken and sworn to do but never carried out."

Mr Cadd, an officer who worked at Turana between 1968 and 1990, said complaints from boys about sexual abuse went "nowhere".

"It didn't exist," he said of the abuse.

"You had suspicions about different things that you couldn't prove, and you definitely knew a lot of the staff that were there shouldn't have been employed in the first place," he said.

"You don't have to be an Einstein to work that out, you only have to talk to some of them."

He added: "I think some people saw the kids there as prey.

"I think there were quite a few that saw bullying as a way of life."

Mr Cadd said he had seen staff destroying files at the centre, but had only become aware of the extent of sexual abuse at Turana after he left.

"Now the commission has opened the tin of worms they're going to have a lot of cases to deal with."

Mr Cadd said the testimony of Robert Cummings on Tuesday, who told the commission he had been subjected to electric shock treatment after reporting a rape, had shocked him.

" I felt ashamed," Mr Cadd said.

As a new employee he had been surprised to see a colleague destroying files, he said. "I was horrified," said Mr Cadd. "I was only new and I knew files were like bibles.

"I said, 'You can't do that'. And he said, 'I was given this stack, they're over 21s'.

"I said, 'They've got to be kept, they've got to go to head office'. He said, 'Nope, this is what I was told to do'. Rip, rip, rip."

Mr Cadd revealed to the commission he had been motivated to speak out after becoming friends through stamp collecting with a man who used to be a Turana inmate.

"You can't rectify what was done in the past but you can damn well make sure it doesn't happen in the future," he said passionately.