"[The] cultural awareness course taught at the academy didn't provide cultural competence," Mr Bell testified Thursday - the final day of the inquest into the death in custody of Ms Dhu, 22, in August 2014.
Ms Dhu, whose first name is not used for cultural reasons, died two days after being locked up at South Hedland Police Station for unpaid fines totalling $3622, stemming from offences including assaulting an officer.
Mr Bell also said detainees should not be detained at the station in WA "for more than 24 hours".
"It's our strong desire not to hold anyone for longer than 24 hours," he said.
She died during her third visit in as many days to the Hedland Health Campus from staphylococcal septicaemia and pneumonia, following an infection in her fractured ribs that spread to her lungs.
West Australian coroner Ros Fogliani has refused to publicly release footage of the dying Aboriginal woman in custody despite her family supporting the idea.
Ms Dhu's family initially opposed media requests to obtain the security footage from the lock-up, which was repeatedly played in court, but their lawyers said on Thursday the family had reconsidered their position and believed it was in the public interest.
However, Coroner Ros Fogliani dismissed the application.
Lawyers for relevant parties in the inquest, including Ms Dhu's family and the police and medical staff who had contact with her, will now provide written submissions to the coroner.
Ms Fogliani is expected to deliver her findings later this year.