A child should never be held in a police cell no matter what they're accused of doing, a doctor specialising in children's health says.
A 13-year-old boy was detained overnight before being transferred to a court cell, where RNZ understands he was held along with violent offenders. Hours later the charges were withdrawn but he was not released until lawyers intervened.
The boy had been charged with endangering transport, which carries a jail term of 14 years.
The police said the he was driving a stolen car extremely dangerously, and that he failed to stop.
By law, police can only hold a 12- or 13 year-old child if they are charged with an offence which has a penalty of 14 years or more.
Otago University paediatrics lecturer Sue Bagshaw, who specialises in young people's health and development, said punishment did not help the root cause of a child's trauma or behaviour.
Putting a child in a cell reinforced their negative feelings, she said.
"It should never be an option."
Dr Bagshaw said it did not help young people learn, deal with traumatic experiences, or with their ability to be part of the community.
Better ways to keep people out of the youth justice system would include paying more attention to school-aged children, she said.
Former children's commissioner and children's advocate, Ian Hassall, said police shouldn't be keeping children in cells.
"It's important that young people not be exposed to that sort of thing because they need to believe they're cared for by the state and its agencies and that they have dignity and the ability to do well as time goes by."
He said while it shouldn't happen he accepted that sometimes the police had no other option.