Figures obtained by RNZ have revealed New Zealand police used spit hoods on 117 children and young people between 2016 and 2020.
Police used the hoods 129 times in total, with seven young people placed in them more than once.
Almost 70 uses were on tamariki and rangatahi Māori, including a child aged just 9 years old in 2018.
Made up of two sections, spit hoods are a one-size-fits-all device designed to stop people biting and spitting at officers.
Children's Commissioner Judge Andrew Becroft described them as a "Guantanamo Bay type invention" and said their use would be highly traumatising.
"Just imagine a 9-year-old ... imagine that sort of technique and that sort of device being strapped to your 9-year-old's head."
Becroft wanted them scrapped for tamariki immediately.
"Frankly, it's profoundly concerning, utterly unacceptable in my view," he said.
"It's morally wrong and the use of spit hoods on young children should be abolished and abolished forthwith."
Justice advocate Julia Whaipooti thought the figures were devastating but was unsurprised at the over-representation of Māori.
"This factually highlights again that there is structural racism in how police police, where they police, and who they police," Whaipooti said.
"We know that with guns, with tasers, with dogs ... with the use of pepper spray, police are more likely to use that on Māori and Pacific than non-Māori."
University of Waikato senior psychology lecturer Armon Tamatea said children coming into contact with police often had difficult upbringings.
"Most likely to have experienced neglect, abuse, been in foster care for example," Tamatea said.
"Maybe even have language or learning difficulties, mental health challenges, and maybe other vulnerabilities as well so that's a likelihood."
Placing a child in a spit hood would likely cause degree of trauma, he said.
"Whether it's psychological trauma because of the frightening experience of having a hood applied over your face, and physical trauma, possibly, with the potential for suffocation.
"What few studies that seem to be out there about the use of this are typically being with healthy adults, I've [seen] nothing done with children probably because there will be ethical issues around doing this kind of research with young people. So those would be the foreseeable issues, in the absence of any hard evidence on this."
The Independent Police Conduct Authority had not received any complaints or police referrals about the young people behind these figures.
Investigations manager Stu Graham said in cases of young children it would be desirable for police to refer them for review.
"So we have a memorandum of understanding with police where we expect certain things to be referred to us. This referral is at the discretion of the commissioner. The situation you've described, the use on a 9, 10-year-old, would be desirable for it to be referred to review. That would depend on the circumstances and ultimately is a matter for police."
Police Association president Chris Cahill said officers dealt with thousands of young offenders every year, meaning the number ending up in hoods was low.
It was not just saliva being spat at officers; some people also spat blood, and the risk was even higher with Covid-19, he said.
"Spitting at a police officer in 2021 could literally be a death sentence with Covid-19 and that's the reality police have to deal with."
Officers who were spat at would worry about diseases they may have caught and the risk it posed to their families.
They may have to undergo testing for a variety of diseases such as hepatitis, and some could take months to return a result.
Police director of community partnerships and prevention Eric Tibbott said spit hoods were a last resort and he was comfortable with how police used them.
Officers would always fill out a tactical options report explaining the rationale behind any decision to use a spit hood, he said.
There would also be oversight from a supervisor, and a third party could check to see whether the hood had been applied in line with legislation and policy.
Tibbott said he could understand the Children's Commissioner's point of view, but he struggled to see any other option.
"So then if you've got concerns over the spitting and biting, and potential for the transmission of diseases that are transmitted by saliva and biting, what alternative measures have we got in play? I'm not sure if there is one."
Spit hoods and Covid-19
It was not known how effective spit hoods are at preventing the spread of Covid-19 as it had not been tested by police.
Tibbott said that was because the hoods were not considered PPE, rather, an option to prevent saliva being spat at someone.
However, spit hoods did have some potential health benefits in terms of stopping the transfer of disease through spit.
Covid-19 would require specialised PPE, and if there was any indication of a Covid-19 risk, the appropriate face covering would be an N95 mask, Tibbott said.
These were available in all custody units for both staff and offenders.