The man who authorised the tear gassing of Northern Territory boys in youth detention says a "tough on crime" political agenda has no chance of reducing reoffending.
Former corrections commissioner Ken Middlebrook ordered six Don Dale Detention Centre detainees to be gassed after one escaped his isolation cell and began trashing property in 2014, a scandal which sparked the NT juvenile justice royal commission.
He told the inquiry that NT incarceration rates are among the worst in the world, but heavy handed punishments have no benefits for rehabilitating youngsters in jail.
"Tough on crime means more numbers, more overcrowding and stress on the system... building prisons is not the answer," Mr Middlebrook said on Wednesday.
"I think we live in a very punitive society where people want their pound of flesh... I often wonder what it's going to be like in another five years here."
Mr Middlebrook said he was embarrassed to be in charge of a system rampantly locking up people, yet he couldn't control government policy.
He said he tried to shift the focus from custody to indigenous community policing support, and said NT prisons struggled with inadequate infrastructure, spiking detainee numbers and a poorly trained and casualised workforce.
Former corrections minister John Elferink and ex chief minister Adam Giles will also give evidence this week.