Girl acquitted of murdering Jason Galleghan due to mental health

A laughing teen girl said to have exhibited “evil inhumanity” as she joined in a vicious gang bashing that claimed a teen’s life has been found not guilty of murder on mental health grounds.

A girl has been found not guilty of the murder of Jason Galleghan (pictured) due to mental health.

A teenage girl has been found not guilty of murdering a defenceless teen in a vicious gang bashing on mental health grounds, despite a judge finding her conduct was “chilling in its evil inhumanity”.

Jason Galleghan, 16, lost his life in a horrific assault meted out by Richard Sione and multiple children who cannot be legally identified at Kayla Dawson’s Doonside home on August 4 2021.

The NSW Supreme Court found Dawson had set Jason up to punish him over her mistaken belief he had stolen her AirPods.

A court has found the murder proven, but ruled the teenage girl was not criminally responsible due to a significant mental impairment.

She was the last defendant charged over Jason’s death to learn her fate after Sione, Dawson, and four other children were earlier jailed.

Richard Sione.

Kayla Dawson.

Chilling video captured by those present shows the relentless assault which left Jason with unsurvivable injuries.

In the video, the teenage girl screams “go hard, stomp on his f--king head” and “finish him off, go go go”.

NSW Supreme Court Justice Robert Hulme remarked on the “sustained and gratuitous savagery” meted out to Jason.

“She taunted and belittled Jason with expletive laden abuse, she made hand gestures towards the camera, laughing,” Justice Hulme said.

“Her conduct and tone was chilling in its evil inhumanity – she repeatedly said she wanted him ‘finished’.”

The recordings played in court also depict the girl screaming at Jason to repeat various youth postcode gang slogans.

The prosecution and the teenage girl’s defence both agreed a mental health defence was made out, though the court was still required to make that finding on its own assessment.

The teen was recorded as presenting with mania when she first entered custody on remand, before she was later admitted as an involuntary patient at a forensic hospital in 2022.

“During the assault she heard a voice telling her to ‘kill him’, referring to Jason,” Justice Hulme said.

“She had the belief that her life was in danger and that ‘the devil was telling people to hurt me’.”

Jason Galleghan.

The teen also reported beliefs others could hear her thoughts, a perception her life was a video game, and belief in spirits and the devil.

A second psychiatric expert diagnosed the teen with bipolar disorder with psychotic features, post-traumatic stress, attention deficit hyperactivity disorder, and polysubstance abuse which is in remission due to her being in custody.

“I am satisfied … the accused had a mental health impairment that had the effect that she did not know that the act was wrong,” Justice Hulme said.

The teenage girl will now be detained in a mental health facility indefinitely.

Earlier this year Justice Hulme found Dawson, then 19, and Richard Sione, 32, guilty of Jason’s murder due to their roles in the joint criminal enterprise, sentencing Sione to at least 24 years’ imprisonment and Dawson to at least 13 years’ imprisonment.

Two boys aged 14 and 15 were convicted of murder and jailed for 15 years and six months, and a 13-year-old boy was also jailed for 14 years and four months.

Another 13-year-old boy convicted of manslaughter in relation to Jason’s death was sentenced to seven years and six months’ imprisonment.

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