"They never told me when I would be getting out": A former detainee tells the royal commission into the Don Dale Youth Detention Centre. (AAP)

"They never told me when I would be getting out": A former detainee tells the royal commission into the Don Dale Youth Detention Centre. (AAP) Source: AAP

Procedures for dealing with kids at risk of self-harm were not being followed more than a decade after a death in custody at Don Dale Youth Detention Centre, a royal commission has been told.

The 15-year-old Aboriginal boy who died at Don Dale in 2000 had been sent there for 28 days under the Northern Territory's controversial mandatory sentencing laws, after stealing stationery worth less than $100.

Barrister John Lawrence QC, who acted for the boy's family during a 2001 coronial inquest into the death, told the NT juvenile justice royal commission the teenager had taken his own life after being locked down in a room on his

own.

Officers were meant to check on him every 30 minutes but the inquest found they shrugged off clear symptoms of mental disturbance.

Mr Lawrence, who is now representing a teenager tear gassed at Don Dale in August 2014, told the inquiry staff working at Don Dale in 2012 did not follow the at-risk guidelines recommended by the coronial inquest into the boy's suicide.

Former Don Dale assistant general manager Michael Yaxley, who was involved in reforming "at risk" policies in the aftermath, disagreed.

"From that coronial (inquest), a lot of the staff that worked there continued on for many years and we took with us the seriousness of at-risk procedures in the Don Dale Centre," he told the inquiry on Thursday.

The CLP government introduced mandatory sentencing for property crimes in 1997, but they were repealed by the Martin Labor government in 2001.

Since then, both Labor and CLP governments have introduced mandatory sentencing law for serious assaults.

In 2012, a girl with a history of self-harm when placed in isolation was put in a high dependency at-risk unit at Don Dale.

The inquiry heard the inmate was only let out of her cell for 30 minutes each day, except for times when she was sufficiently well behaved to attend school.

In March 2015, the girl self-harmed six times over five days after being locked down yet again.

She was hospitalised three times during that period after trying to kill herself, yet wasn't seen by a mental health expert for four days.

The girl, known as AN, repeatedly pleaded to be let out of her cell and told the inquiry that she felt "dying was better than staying in isolation".

MORE ON DON DALE Don Dale girl's self harm 'out of control' More harrowing stories emerge from former Don Dale corrections facility. Young Aboriginal girl hospitalised for weeks after Don Dale ‘incident’ EXCLUSIVE: A Northern Territory family says the system has failed in its duty of care after their child was hospitalised and held for more than three weeks following an incident in Darwin's Don Dale Youth Detention Centre.

NT govt won't pay costs in Don Dale suit

The Northern Territory government will not have to pay some court costs of a civil lawsuit filed by a group of former Don Dale Youth Detention Centre inmates who were tear-gassed.

Four teenagers from Darwin's youth prison were last week awarded $53,000 in compensation after they were spit-hooded and shackled, but the judge ruled tear- gassing them was both "reasonable and necessary".

The boys, who cannot be named, sued the NT government over their August 2014 treatment, arguing it amounted to assault and battery, however Justice Judith Kelly found mostly in favour of the defendant.

In the NT Supreme Court on Thursday, Master Vince Luppino also dismissed the plaintiffs' application for court costs of a settlement conference.

In November 2015, the NT government rejected the plaintiffs' offer of a $95,000 settlement plus court costs and made no counter offer, so the matter proceeded to court.

Master Luppino said the government had a "very strong defence" and isn't compelled to make an offer where it considers its opponent's position as "unlikely to succeed or having little merit".

Lawyers for the former inmates were only successful in one claim, and last week Justice Kelly ordered the government to pay three of the boys $12,000 each in damages, while the fourth received $17,000.

They were among six teens who were gassed after one inmate, Jake Roper, escaped from his solitary confinement cell and began trashing an exercise yard.

Justice Kelly did not award damages for the use of gas, police dogs or guards in riot gear as she ruled they were reasonable and necessary to "temporarily incapacitate Jake Roper and so bring the crisis to a close before it escalated even further".

Five of the six boys had been held in isolation for up to 17 days straight after earlier escaping from the centre.

In handycam footage captured moments before the gas was sprayed, one guard can be heard saying, "I'll pulverise the little f*****."

Footage of the incident was aired on national television last year, prompting Prime Minister Malcolm Turnbull to call a royal commission into the juvenile justice system.

The detainees were later transferred to Berrimah adult prison and subjected to "acts of battery", Justice Kelly said.

"In addition to handcuffing the plaintiffs behind rather than in front, the defendant wrongfully applied shackles and a spit hood to each plaintiff," she said.

"I have no doubt that this would have caused the plaintiffs considerable distress and humiliation, especially as youths being marched past adult prisoners."

But Justice Kelly said the guards' conduct was not "knowingly malicious, violent, cruel... an abuse of power or indeed knowingly wrongful at all".