NEW SOUTH WALES — Biddy Porter, 10, died from multiple injuries on July 8, 2020, at a rural property in New South Wales during school holidays. A 14-year-old girl killed Porter in a farmhouse while they were alone.

The Supreme Court of NSW ruled in 2021 that the teenager was not criminally responsible due to a diagnosed mental illness. Two psychiatrists determined she had schizophrenia and was experiencing acute psychosis at the time of Porter's death. She has remained in custody under the supervision of a mental health review tribunal since her arrest.

An inquest is investigating potential systemic failures and early warning signs related to the death of Porter. Counsel assisting Peggy Dwyer SC testified at the Lidcombe coroner's court that the teenager likely experienced delusions and a loss of contact with reality. Dwyer outlined that she engaged in self-harm and developed an interest in knives prior to the death.

In June 2019, the teenager killed six chickens on her family's property. Her parents responded by removing her bedroom door and breaking a video game in half. The teenager's mother testified about the incident: "The chickens were to be culled, so that was what was happening to them anyway."

Two weeks before Porter's death, the teenager told her mother she thought about killing people frequently. She also reported intrusive thoughts about killing her parents and sibling. Her mother consulted a naturopathic herbalist about her daughter's behavior before the death, and the herbalist advised her to schedule an appointment with a general practitioner.

A general practitioner issued a medical referral for a psychiatrist in Sydney. The teenager killed Porter one week after this medical appointment. Her mother located the psychiatrist referral in an email spam folder after the first day of the inquest. She testified: "Mental health was never on my radar. I never believed in mental health, I didn’t understand mental health so it didn’t come up to me as something I needed to do." She also stated: "I don’t understand why that was such a big red flag." NSW state coroner Teresa O’Sullivan is presiding over the proceedings.