Natalie Jade Whitehead, 38, pleaded guilty in Brisbane Supreme Court on Thursday to manslaughter, failing to provide the necessities of life and negligent act causing harm.
Crown Prosecutor Matt LeGrand said Whitehead had left her son Dexter and another baby in a cot together with one bottle between them some time after June 16, 2019.
"She and the (alleged) co-defendant were taking drugs. They were not attending to the babies' needs. That is evident in the malnutrition and nappy rash," Mr LeGrand said.
Whitehead called triple zero at 5.42pm on June 21 and told the operator that her baby was "completely gone".
When paramedics attended Whitehead's home at Raceview in Ipswich, west of Brisbane, they found her holding Dexter and crying.
The surviving baby cannot be named for legal reasons.
Mr LeGrand said Dexter had died after suffering the severe neglect of his most basic needs in the form of food and fluids.
"The hours preceding death would have been extremely distressing both physically and emotionally," Mr LeGrand said.
Mr LeGrand said Whitehead required a sentence that would denounce her conduct and remind parents that taking illegal drugs left them unfit for their responsibilities.
Defence barrister Joshua Fenton said Whitehead's drug use had increased over the years as she entered a number of relationships where she was the victim of domestic violence.
"There is some evidence of remorse. She was certainly distressed on the triple zero call and at the scene," Mr Fenton said.
Whitehead wiped away tears as Mr Fenton said she had shown symptoms of post-traumatic stress disorder while in custody.
"She has taken steps to address her somewhat limited life skills and drug offending," Mr Fenton said.
Justice Catherine Muir sentenced Whitehead to a total of nine years' imprisonment with her three years and nine months already spent in custody as time served.
Justice Muir ordered Whitehead to be eligible for parole in June 2025.
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