Scott Andrew Cabrie, 47, was reported missing from his home at Toogoom on Queensland's Fraser Coast on February 6, 2023.
Mr Cabrie's body was later found at a boat ramp at the nearby town of Howard.
Prosecutors have alleged a 17-year-old and 18-year-old fatally stabbed him during an Uber ride on February 7.
A blue Nissan X-Trail SUV used by Mr Cabrie was found burnt at another location at Pacific Haven.
The younger defendant, now aged 18, faced Brisbane Supreme Court on Monday for arraignment on charges of armed robbery in company with violence, vehicle theft, arson and murder.
The youth replied " guilty, Your Honour," when asked to enter a plea on each charge.
Prosecutor Chris Cook sought an adjournment to obtain pre-sentencing and psychological reports.
The youth's defence barrister also sought a report into the time her client had spent in separation while in youth detention.
Separating a youth detainee from other detainees is a measure that can be taken for medical or safety reasons.
Justice Peter Davis adjourned the sentencing for a date to be fixed and the matter will next be heard on April 22.
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