Youth workers, cops, judges face NT probe

The Northern Territory juvenile justice royal commission is set to hear from police, social workers, judges and lawyers as Darwin hearings continue.

On Tuesday the inquiry heard NT police didn't charge Don Dale Detention Centre guard Conan Zamolo with assault because he believed he was just "goofing around".

"His maturity level was only one notch above the children he was working with," Detective Sergeant Kirsten Engels said.

An inmate identified as AT told police he was "clotheslined" by one guard and then chased into his cell by Mr Zamolo, who hit him on the kneecaps with a torch.

Three separate detainees also told police Mr Zamolo recorded one child masturbating in the shower and then posted the footage to social media app Snapchat in 2014.

Police investigated the claims, including allegations he'd bribed kids to fight each other for junk food, but the bodybuilder was only charged with steroid possession.

Det Sgt Engels told the inquiry she didn't press any charges because she didn't think the boys' evidence was strong enough to win a criminal court case.

She also believed the intent to assault wasn't there, based on an unsubstantiated theory that Mr Zamolo thought he was playing a game with the detainee he hit with the torch.

This week the commission is slated to hear from 31 witnesses including police officers, judges, lawyers and academics.