"The devil has gone now," a refugee and former Kenyan presidential candidate said after punching his son in the stomach and throwing the three-year-old against a bathroom wall.
Quincy Zuma Wambitta Timberlake was sentenced on Friday for the manslaughter of Sinclair, who died on his bedroom floor at Kallangur, north of Brisbane, in June 2014.
After finding his son apparently fallen at the bottom of stairs, Timberlake started saying that the devil was in the house, the Brisbane Supreme Court heard on Friday.
The now 43-year-old grabbed a Bible from his bedroom, saying he was going to slap the devil, Justice Paul Freeburn said in sentencing Timberlake over the "brutal and incomprehensible" death.
Sinclair's mother Esther assumed her husband was going downstairs but heard her son yelling and thuds from behind the bathroom door when she got out the shower.
When the door opened the little boy seemed to be in pain and doubled over.
Timberlake struck him forcefully in the stomach causing him to stumble, then said: "There's a devil in his stomach, I'm hitting the demon out of his stomach."
When Sinclair started to go towards his mother, Timberlake in a rage threw the child against the wall.
After the boy fell to the ground he told his wife "the devil has gone now" before rambling about beating the demon and removing it from Sinclair's stomach.
Emergency services found Sinclair's lifeless body on the bedroom floor.
The couple omitted to tell authorities about what occurred in the bathroom but Timberlake was secretly recorded in the morgue making biblical references while repeatedly apologising for failing Sinclair.
Weeks after the death, Esther Timberlake - who was immediately released on parole after pleading guilty in 2019 to being an accessory to her son's manslaughter - told police about the attack, saying her husband was experiencing delusions.
After being forced to live on the streets and subject to abuse as a child, Timberlake obtained a chemical engineering degree before meeting his Kenyan wife Esther who had returned to Africa after being admitted to the legal profession in Australia.
Timberlake was arrested and jailed having announced his intention to run as president after the couple formed the PlaCenta Party (Platinum Centraliser and Unionist Party) of Kenya.
He reported being badly beaten and tortured by police and a Kenyan militia group.
The charges were dismissed but the couple left the country as they were vilified and persecuted.
Esther Timberlake and their youngest child, then Sinclair with a friend, travelled to Australia from Dubai, and Quincy eventually arrived on an illegal boat.
Timberlake, who has been diagnosed with post-traumatic stress disorder, was sentenced on the basis he punched his son intending to cause grievous bodily harm but that at that time he was of diminished responsibility.
"That is, at the time of doing the act which caused Sinclair's death, you were in such a state of abnormality of mind as substantially to impair your capacity to know that you ought not to do the act," Justice Freeburn said.
He sentenced Timberlake, who pleaded guilty to manslaughter, to 11 years behind bars.
Justice Freeburn declared he be eligible for immediate parole after serving more than nine years in custody.
"The release of Mr Timberlake is now a matter for the Parole Board," Justice Freeburn said.
Timberlake's immigration status means he will be immediately liable for either deportation or detention for an indefinite period.
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