A teenager who was tear-gassed, spit hooded and shackled to a restraint chair in the Northern Territory's youth prison system says he was regularly "punished" by not being given access to food, water and toilets.
Dylan Voller, whose treatment sparked the NT's royal commission into juvenile justice, came out of adult jail to give evidence on Monday.
The 19-year-old said he was forced to defecate in his pillow slip after an Alice Springs Youth Detention Centre officer refused to take him to the toilet.
"I had been asking for at least four or five hours ... I was busting," he told the NT Supreme Court.
Voller described the regular practice of strip searching boys as young as 11 or 12, without explaination, he said.
"Only when I got older I realised why it was happening but the first year of me going in and out, I didn't really know what it was for, why," he said.
"They would come in, tell you to strip all your clothes off, take all your clothes off, then they wouldn't let you cover your private parts, they'd tell you you have to put your arms up in the air, turn your arms up and down, show under your armpits, like pull your ears back, put your finger in your mouth and run your finger around your gums and poke your tongue out.
"Then run your fingers through your hair and then turn around, lift one foot up, lift the other foot up, then squat and cough."
He recalled one night when he was left "with no clothes, no mattress, no sheets, no nothing, for the period of the whole night" in a cell with the air conditioning turned up.
"I was freezing all night," Voller said.
"I was pressing the button, actually crying asking for a blanket, asking for a sheet. I was that cold, my skin was going all wrinkly and shivering.
"I remember one more clearly where they left me with just the mattress, nothing else. No clothes, no jocks.
"I ended up trying to wrap myself up in the foam mattress, because it was a foam mattress, I was trying to wrap myself up with the mattress."
Voller told the commission it was not uncommon for him to be deprived of food and water as a punishment.
"There was a time in the BMU, not far from the tear gas incident where an officer walked in and gave everyone else water, because that officer didn't really like me, he said 'Do you want water, Voller?' I said yes," he said.
A still from the ABC Four Corners episode showing Don Dale detainee Dylan Voller strapped into a mechanical restraint chair. Source: ABC Australia
"As he was walking out, he threw water on to the ground and said 'There you go' and walked off.
"Because I was swearing, they'd punish me and wouldn't give me dinner.
"I'd have to wait until the next day or they wouldn't give me breakfast or lunch depending on what time of day it was.
"There was one instance where an officer seen how hungry I was in the middle of the night, he was on night-shift, come around at 1, 2 o'clock in the morning, chuck muesli bars through the hatch and said 'Here, eat' and make me toast because he could see how hungry I was.
"He didn't agree with what they did by starving me, I guess."
Voller said the inmates at Don Dale were charged "rent" which was taken out of the money they could earn each day for good behaviour.
This money went towards buying everything from underpants, shampoo and deoderant to CDs and shoes.
"If you don't buy your own underwear, the only other underwear you have the choice of wearing is the underwear everyone else wears, it gets washed, you pick out another pair, it gets washed and it goes through all of the males in Don Dale," he said.
The inquiry comes after footage screened in July showed Voller and five other boys being tear-gassed at Darwin's notorious Don Dale detention centre two years ago.
Voller was jailed in 2014 for a violent drug-fuelled binge. He will not be cross-examined despite making allegations against 31 guards.
He is concerned about giving evidence while still in custody, and fears repercussions from prison guards.
A youth identified as AD gave confidential evidence on Friday after the NT government last week lost a bid to delay further witnesses.
Last week the commission tried to exclude local reporters from a tour of the old and new Don Dale centres with co-commissioners Margaret White and Mick Gooda, prompting the press to walk out of the hearings in protest.
Complaints from Chief Minister Michael Gunner's office eventually reversed the decision and allowed press access.
It comes as Sky News reports the commission is paying a private spin doctor more than $1100 a day amid rumblings about the need for a 12-month extension beyond the March 31 deadline.
The extension would lead to a budget blowout for the inquiry, which is being jointly funded by the NT and federal governments and is so far estimated to cost $50 million.
