Police have admitted that officers in Canterbury got it wrong when they left a woman alone despite her threats to hurt herself.
The Independent Police Conduct Authority said a woman told officers she was planning on self-harming.
The officers told staff at the station, but no-one stayed with the woman, the authority said.
While waiting to be admitted to a cell, the woman tried to hurt herself.
"This was noticed immediately and appropriate steps were taken to ensure she was safe.
"The authority worked with police to ensure involved staff engaged in a formal debrief with senior officers to reconfirm expectations regarding oversight of distressed people," the authority said.
Canterbury district commander Superintendent John Price said police accepted the officers involved did not follow proper procedures.
He said there were robust policies in place, the officers have received extra training and a refresher training course was being prepared for district-wide staff.
"In this particular incident we accept the officers involved did not follow the proper procedures, and they have been dealt with through professional discussions and reinforced training," Mr Price said.
"Work has also been done to engage wider staff in Canterbury with refresher training, to reinforce the expectations and obligations around dealing with distressed people."
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