Ms McLeod and her four children, Aaleyn, 6, Matilda, 5, Wyatt, 4, and Zaidok, 2, were killed when her small SUV was involved in a head-on collision with a truck on May 27, 2019, on the Bunya Highway at Kingaroy northwest of Brisbane.
A woman who spent time in the McLeod home told the inquest, which opened in Brisbane on Wednesday, she saw James McLeod ask one of his daughters to perform an indecent act.
Counsel assisting the coroner Kylie Hillard asked the woman about a statement she made in June 2019 alleging she had witnessed "highly inappropriate" behaviour by Mr McLeod towards Matilda, as well as Ms McLeod saying he had raped her.
Mr McLeod's barrister Amelia Hughes challenged the witness's evidence and asked her if she made up the offending against Matilda because she did not like her client.
"I have not lied about this incident," the witness, who cannot be identified, responded.
The witness said she did "all I could" about the incident at the time by talking to Ms McLeod, who dismissed it. The witness did not take her concerns to authorities.
In her opening statement to the inquest, Ms Hillard said police found a handwritten note in Ms McLeod's purse at the crash scene.
"In the note, she stated she had been unable to cope, being worried about the fate of her children and that she had sought help ... it referred to complaints of rape, complaints of two of her children being molested," Ms Hillard said.
She said Ms McLeod had a long history of mental health problems, including schizophrenia, chronic suicidal ideation and suicide attempts going back to 2009, but the crash could not "simply dismissed as suicide" or a premeditated murder-suicide.
"It was a fateful note - that investigators were lucky to find, given the state of the car," Ms Hillard said.
She said Matilda had complained about being sexually assaulted and Wyatt had started displaying sexualised behaviour.
The inquest will look at the adequacy of the police responses to the complaints of domestic and family violence within the McLeod family and the responses by the health system around Ms McLeod's care and the actions of child protection agencies.
Senior Constable James McKinley testified speed or a collision with an animal did not appear to be factors in the crash but both vehicles were travelling at 100km/h, which led to a "substantial impact".
Sen Const McKinley said he found Ms McLeod's note in a pink purse about five metres from her crashed vehicle.
A senior family support worker, who cannot be named for legal reasons, testified she had interviewed a terrified Ms McLeod after she sought shelter from alleged domestic violence by her partner.
"She said she had been to the police as the alleged PUV (person using violence) had been driving past and making gestures of a gun to the head and cutting across the neck ... she said the police told her she should not take the children away from their father," the support worker said.
The worker said the children seemed to be very happy after moving into the family shelter and did not appear to be afraid of Ms McLeod.
Sunshine Coast University Hospital clinical director of mental health, Chris Lilley, testified he had seen Ms McLeod after she had attempted suicide and said people with schizophrenia were prone to auditory hallucinations, disordered thinking and delusional thoughts.
Dr Lilley said it was possible for people with schizophrenia to have a genuine belief non-existent events had happened and to have periods with no obvious symptoms.
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