Northern Territory child protection and related agencies "failed to deliver the care" an Indigenous teenager needed before she took her own life, a coroner has found.

The 17-year-old Bilinarra girl, referred to as Didbala, was under a Long Term Protection Order in the care of the Chief Executive Officer of Territory Families when she died. She had been placed in the CASPA-managed Intensive Therapeutic Residential Care (ITRC) house in Katherine (Katherine CASPA).

Coroner Elisabeth Armitage said Didbala's "young life was not an easy one". She had been diagnosed with psychosis and Foetal Alcohol Syndrome, for which she had been on medication. Territory Families had received 19 notifications concerning her welfare since she was one year old.

On the evening of 2 October 2022, Didbala left the Katherine CASPA facility and met up with friends to smoke marijuana and drink beer supplied by a man they did not previously know. Police later returned her to the facility after she asked to be taken home after her friends had noted she had been talking to herself.

Later that night, carers heard Didbala screaming that she could "hear voices and she wanted to be taken to Darwin". She struck a carer with a vase, prompting them to call police — but failed to inform officers that Didbala was "hearing voices, or was otherwise mentally unwell, or at risk of self-harm".

When police arrived, the same carer then told them Didbala was hearing voices. In her final report, Judge Armitage said: "The police understood they were attending for an assault and property damage, more so than for mental health, but in any event their 'main priority was actually [Didbala]. We were trying to locate her and speak to her and sight her'."

When they arrived, Didbala was locked in her room, and no keys could open the door. A Shift Sergeant arrived and kicked down the door 24 minutes after police had first arrived. Inside, he found Didbala had self harmed. She was declared dead one hour later.

In her findings, Judge Armitage said, "Didbala's mental health gave rise to a chronic elevated risk of suicide and self-harm. Her consumption of gunja, alcohol and the acute changes in her behaviour shortly before she took her life, pointed to an elevated risk of suicide or self-harm that day, but this was not identified by her Carers and it was not communicated to attending police".

She found "a failure to appreciate her level of risk, and a mistaken belief that she was preventing their entry, contributed to a delayed entry into her room".

"Her Carers and the attending police are devastated that they could not save her," the Coroner added.

One of the police officers told the inquest that had she "understood there were self-harm concerns, she would have called the Shift Sergeant straight away and probably forced the door open immediately." However, "no-one, including the CASPA workers, appreciated that the circumstances gave rise to an elevated risk of self-harm".

Judge Armitage said Didbala had suffered from "serious mental illness which posed significant challenges for her and those who cared for her, including [her] family, health professionals and statutory carers".

"Didbala's mental health gave rise to a chronic elevated risk of suicide and self-harm," she said, noting that while in the CEO's care, Didbala was "subjected to an array of Case Managers, when she would have benefited from consistency".

"Despite the efforts of dedicated individuals, the services and care provided by Territory Families was rarely sufficient to meet Didbala's needs, and in particular Territory Families failed to properly accommodate Didbala's drive to be with her family. In making this finding, I acknowledge that providing care and services to Didbala was highly challenging," she added.

"Didbala's determination to be with family, irrespective of the plans that were put in place for her, made it essential for Territory Families to work closely and collaboratively with her family but this was not reflected in their approach to her care."

Judge Armitage said case managers in the Big Rivers Region carried workloads so heavy they could "never hope to properly consider and address her needs," and funding models lacked flexibility to seek alternative case management.

"Consequently, she suffered from Case Management neglect," Judge Armitage said, adding that although Didbala received "high-quality mental health interventions", they were poorly coordinated.

Amongst her 16 recommendations, the Coroner called on CASPA to ensure that its workers inform first responders that a "Risk of Self Harm or Suicide" exists for all children in their care; NT Police, Territory Families and CASPA "take steps to review, update and implement the 'Protocol for Police Contact with Children Living in Intensive Therapeutic Residential Care''; and NT Police ensure all frontline police receive expert training on the circumstances, behaviours, and risks of vulnerable children in OOHC.

Furthermore, she called on Territory Families to review their funding model for Intensive Therapeutic Residential Care, and ensure Territory Families both provide each child in their care a Case Manager with a "realistically manageable case load" and address the "chronically unfilled Case Management needs in the Big Rivers Region".

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This article was updated on August 13 to note the same carer who made the phone call to police, told officers when they arrived that Didbala was hearing voices.