Prosecutors are still unsure why a young man entered his uncle's unit and murdered him in a "horrific" manner.
Christopher William George Gaffney faced Brisbane Supreme Court on Monday for sentencing after pleading guilty to the murder of Paul Morrow on the morning of January 6, 2020.
Crown prosecutor Nathan Crane said Mr Morrow, 45, was in bed in his unit in the Brisbane coastal suburb of Wynnum after consuming a significant amount of alcohol with friends.
Gaffney, aged 24 at the time, had purchased methamphetamine before he was seen approaching Mr Morrow's unit at midnight while his guests were still there but did not enter.
Gaffney then caught a series of trains and ended up back at Wynnum before 8am.
Mr Crane said Mr Morrow had gone to bed after his guests left at 2am and had a blood alcohol concentration twice the limit for driving, which explained why he might not have heard Gaffney enter his unit or been able to get up and defend himself.
"It does not speak to there being any conversation," Mr Crane said.
He said Gaffney had armed himself with a piece of timber from Mr Morrow's yard and hit him in the head at least twice, according to the pathologist's report.
"There was a significant laceration on his forehead and significant fractures to his (eye socket), nose and skull," Mr Crane said.
Gaffney left the blood-soaked piece of timber beside Mr Morrow's bed and covered his body with a doona before leaving.
Gaffney's DNA was left behind on the timber and Mr Morrow's blood was found on his pants.
Gaffney was interviewed by police and had spoken about having a pre-occupation with Mr Morrow, but the prosecutor said parts of his account were contradicted by other evidence.
"We have what might be some features of a motive but (Gaffney) might not have disclosed the true motive," Mr Crane said.
Gaffney's barrister Colin Reid said his client had been supported in custody by his family and this would continue during his prison term and after release.
"He has indicated his remorse and he understands the very serious nature of the offences and the consequences," Mr Reid said.
Chief Justice Helen Bowskill said it was a tragic case and that Gaffney had a previously good relationship with Mr Morrow and had spent time living at his unit but had then decided to inflict shocking injuries upon him.
"These were horrific events ... you have taken responsibility for this terrible act," Justice Bowskill said.
Justice Bowskill said Gaffney had a serious drug addiction and had been diagnosed with drug-induced psychosis.
"It's a reminder of the damages of drugs that cause you to completely lose control," Justice Bowskill said.
She said she was legally required to sentence Gaffney to life in prison with parole after 20 years.
Gaffney will be eligible for parole in 2041 due to his previous two-and-half years in custody.
