Footage of boys being tear-gassed, spit-hooded and shackled last year at the Don Dale Detention Centre in Darwin launched the inquiry.
Now, a former detainee, Jamal Turner, has alleged a former Alice Springs detention centre guard, Derek Tasker, choked him at the age of 14 when he tried to pat a dog.
"Because I went to pat the dog, and he was holding me at the time, and he thought I was trying to escape, escape custody. He grabbed me by the throat and choked me up against the wall."
He says prison guards at the Aranda Youth Detention Centre regularly assaulted him and other inmates as young as 13.
"Like a knee in the back. Putting the handcuffs on the ground to restrain them, putting their knee in their back, just putting all their weight on the kids, seemed too much force really."
A former Don Dale shift supervisor, Trevor Hansen, was questioned about what he called a "one person escort."
Mr Hansen told the commission the manoeuvre involved picking the youths up with one hand on their shorts and the other on their arm, and forcing them in a "forward direction."
He acknowledged other officers referred to it as a "wedgie".
Questioning him was Senior Counsel Assisting, Peter Callaghan SC.
(Hansen:) "I had heard other officers use that term, yes."
(Callaghan:) "Was it a source of amusement?"
(Hansen:) "I never laughed at it."
(Callaghan:) "Did you see others laughing at it?"
(Hansen:) "Um ... I obviously can't answer that. I don't know what they were laughing at. I mean, if they said something, it could have been (about) something else. I don't ... don't recall."
The commission was instigated in September after footage of the treatment of young inmates aired on national television.
Among them was 19-year-old Dylan Voller, granted bail last month to begin a rehabilitation program, months ahead of his planned release in October.
Speaking outside the hearings in Alice Springs, Mr Voller says he wants to show support to other vulnerable witnesses giving evidence at the commission.
"To support all the other young people giving their evidence, because everyone else around the country and around the world supported me so it's my turn to give back while I've got an open voice."
At a directions hearing last week, the commissioners demanded to know how the media acquired a document appearing to show a list of people Mr Voller once wanted to kill.
Commissioner Margaret White has asked Northern Territory government counsel Sonia Brownhill to provide further information on the leak this week.
