A man who was experiencing a hypomanic episode when he inflicted "extreme and personal violence" on his younger brother by bashing him to death with a spanner has been jailed for 10 years for manslaughter.
WARNING: This story contains graphic content that may disturb some readers.
Michel Willemyns, 62, was originally charged with the murder of Patrick Willemyns at his home in Karana Downs, in Brisbane, in March 2017.
The 53-year-old died of blunt-force trauma after his brother broke into his home and attacked him while he lay on his couch, striking him twice in the head with the metal tool, and stomping on him repeatedly over several hours.
On Friday, Willemyns pleaded guilty to the lesser charge of manslaughter by reason of diminished responsibility in the Supreme Court.
A sentencing hearing held in Brisbane was told Willemyns had been suffering from borderline affective disorder, which was undiagnosed and had been experiencing a hypomanic episode at the time.
The court heard the two brothers had a "close and loving relationship" up until 2016 when their mother passed away, and in the year before this, Willemyns mental health had started to decline.
Crown prosecutor Matt LeGrand told the court Willemyns' use of alcohol and cannabis also started to escalate, causing him to believe his brother owed him money, had stolen his passport and had been harassing him.
"He had developed a paranoia," he said.
The court heard after the attack, he had recorded himself speaking with his "severely injured" brother in what was described as "distressing" and "disturbing" footage.
Mr LeGrand said it was accepted Willemyns had not intended to kill his brother and his moral culpability was reduced due to his state of mind at the time, but he had not been "entirely excused from criminal responsibility".
"The impact of the offending was nothing less than catastrophic," he said.
"It was not entirely unpremeditated."
'An abnormal state of mind'
Defence lawyer Catherine Morgan said her client had lived a successful life working as a university academic overseas and was a "well respected" and "productive member of society" until he began to struggle with depression and alcohol use in 2015.
"His mental health was deteriorating, his personal life and professional life completely unravelled," she said.
"By the time of this offending … he was homeless, he was unemployed he was very unwell physically and mentally."
The court heard while in custody he spent two years in a high security mental health facility receiving treatment and continues to be medicated for his disorder.
Ms Morgan said her client acknowledged he was in an "abnormal state of mind" at the time and was genuinely remorseful.
"This man is acutely aware that he took the life of his brother and accepts responsibility for his actions," she said.
Justice Melanie Hindman accepted Willemyns' mental health had "substantially impaired your capacity to know that you ought not do what you did".
"You held false beliefs, your behaviour was erratic, manic, certainly abnormal," she said.
"Your downward spiral culminated in the tragic and bizarre circumstances where you killed your only brother."
Justice Hindman described the offending as "an exceptionally serious example" of manslaughter.
"The attack on Patrick involved extreme and personal violence," she said.
"Patrick must have suffered terribly throughout the ordeal."
Willemyns was handed a 10-year sentence, automatically deeming him a serious violent offender, meaning he will have to serve at least 80 per cent of his jail term.
After handing down her sentence, Justice Hindman said "good luck, Mr Willemyns".
