The jury on Tuesday heard the prosecution's closing statement following the 19-day murder trial of Maree Mavis Crabtree in Brisbane Supreme Court.
The 59-year-old is accused of killing her 26-year-old son Jonathan with an overdose of painkillers on July 19, 2017 in the family's home north of the Gold Coast before making a $125,000 insurance claim.
She has also been accused of attempting to murder her son in January of the same year.
The jury heard Crabtree's adult daughter Tara claim she watched the hallway and kitchen where her mother crushed up prescription painkillers and anti-anxiety tablets while Jonathan was passed out in bed.
Tara's testimony should be accepted despite her diminished intellectual capacity and the defence's repeatedly suggesting she was a liar, crown prosecutor Caroline Marco told the jury.
"There is a lot of other evidence ... which when combined with what Tara says she saw her mother do, we say shows Tara's evidence to be honest and reliable and the defendant is guilty," Ms Marco said.
Crabtree had wanted to kill her son because she feared losing the family home in a lawsuit brought by a woman who was affected by Jonathan's robbery of a pharmacy, Ms Marco told the jury.
Jonathan was also a violent drug addict with a traumatic brain injury who could not be evicted as he partly owned the house.
Crabtree had told a neighbour "I wish Jonathan had died in the car accident. I wish he was dead," Ms Marco said.
Crabtree had been stockpiling Tara's oxycodone medication and Jonathan was found in his room dead from an overdose with no signs of the painkiller around his body, the jury heard.
Tara, who was one year younger than Jonathan at the time he died, had also been living in the family home with Crabtree.
The jury previously watched nearly five hours of video testimony from Tara that was pre-recorded in late April.
Tara's affairs were managed by her mother to the extent she did not know she had her own bank account, Ms Marco told the jury.
"Tara did what her mother asked her to do because they had a very unhealthy relationship, where she controlled Tara," the prosecutor said.
"She likened it to a relationship of domestic abuse or control."
Crabtree had told Tara not to help Jonathan if she heard him struggling after drinking the drug-laced smoothie and after he died she should tell police it was a suicide, Ms Marco said.
Tara had waited two-and-a-half years to change her story because she was angry at police for keeping her confined in hospital for seven months, the jury heard.
Tara has been granted immunity from prosecution in exchange for her testimony,
Defence barrister Angus Edwards is due to start his closing statement later on Tuesday or Wednesday.
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