Lavinia Alison Murray, 24, pleaded guilty on Wednesday in Brisbane Supreme Court to the manslaughter of her daughter Trinity on February 5, 2021 at Murgon, northwest of Queensland's Sunshine Coast.
Crown prosecutor Caroline Marco said Murray had put Trinity in a bath in the laundry sink at about 9am and used a pair of children's underwear to wash her.
"She turned the tap on and moved the spout to the side of the tub. There was no plug in the drain," Ms Marco said.
Trinity remained in the tub unsupervised and lying on her back with the water running while Murray attended to her other children, cleaned the house and exchanged text messages.
Ms Marco said Murray checked on Trinity three times but then realised she was not making any noise after 9.39am.
"The underpants had blocked the drain and sink had filled up with water up to Trinity's ears and cheeks. she had turned purple in colour," Ms Marco said.
Ms Marco said Murray should never have left Trinity in the bath unattended for any period of time.
"Ms Murray's actions amount to a breach of the duty she held ... That is the basis for her criminal responsibility," she said.
Ms Marco read from victim impact statements from Trinity's father and paternal grandmother.
The father said Trinity's death caused him to turn to drugs and alcohol, which led to further time in custody and missing his daughter's funeral.
"This left me lost and alone, unable to process what happened," he said.
Trinity's grandmother said she had been a happy and smiling baby who loved to visit people.
"I wake up from sleep hearing her little laugh ... She has lost her life and I feel as though I have lost a part of mine too," she said.
Defence barrister Joseph Briggs said Murray has faced much adversity, having an abusive childhood, a mild intellectual disability and had suffered domestic violence.
"Her disability meant she had difficulty planning, co-ordinating and concentrating," Mr Briggs said.
He said police reports showed Murray had been receiving phone calls threatening to seriously injure and kill her in the days leading up to Trinity's drowning.
"The effect on Ms Murray may well have been significant," Mr Briggs said.
He said Murray had been struggling to cope with caring for children as a young single mother and made candid admissions to police.
Justice Paul Freeburn told Murray she was responsible for causing the death of a defenceless and vulnerable baby but he accepted she was remorseful.
"This is a tragedy you will have to live with for rest of your life ... it has had devastating consequences for you, the father and your family," he said.
Murray was sentenced to five years' imprisonment to be suspended after serving 12 months in custody.
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