The Brisbane Supreme Court jury on Tuesday heard the closing statements following the 19-day murder trial of Maree Mavis Crabtree.
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 that year.
There were three other possibilities for Jonathan's death other than Crabtree being a murderer, defence barrister Angus Edwards told the jury.
"He died of a drug overdose. We know that. He was a drug addict. Was it a suicide or accidental overdose?" Mr Edwards said.
Jonathan had tried to take his own life multiple times and with multiple methods for years, the jury heard.
His mental health had deteriorated after he acquired a traumatic brain injury in a car crash and started acting violently to his mother and sister.
"Jonathan had a lot of demons. If he was a good person, he wasn't any more," Mr Edwards said.
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 said.
Jonathan was also a violent drug addict with a traumatic brain injury who could not be evicted as he partly owned the house.
Tara was the only person saying her mother killed Jonathan and she had the most to gain from her murder conviction
"Did Tara kill Jonathan? He had been violent towards her with a brick in hand," Mr Edwards said.
"Did he kill two birds with one stone? She now gets the house to herself."
Crabtree had told a neighbour "I wish Jonathan had died in the car accident. I wish he was dead," the jury heard.
Mr Edwards said Crabtree's statements had been "taken out of context."
Crabtree had been stockpiling Tara's oxycodone medication and Jonathan was found in his room dead 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.
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.
Mr Edwards is due to continue his closing statement on Wednesday.
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