Up all night celebrating the New Year, a man later took his four-year-old son for a trip to the park on a motorbike.
The man was affected by drugs, unlicensed, on parole and riding an unregistered vehicle.
"You'd been out all night on New Year's Eve and when you got home your son begged you to go to the park," Judge Paul Smith said in Brisbane District Court on Thursday.
"You didn't think clearly and when you placed him on the bike you were excited for him."
The man rode off after 7pm on January 1, 2022, with the child sitting between him and the handlebars.
The boy was wearing an adult-sized helmet and no protective clothing.
Struggling to operate the bike, the man went through a red light before approaching an intersection north of Brisbane.
Suddenly a 4WD failed to give way and pulled out in front of the motorcycle.
The man and child were thrown from the bike when it struck the rear of the truck, unable to stop in time despite travelling at less than 50km/h in a 60km/h zone.
More than a year after the crash, the man - now 34 - wept as his son's injuries were detailed at his sentencing on Thursday.
The child was taken to hospital with critical head injuries and a diagnosis indicating "impending brain death".
The boy underwent surgery with a severe traumatic brain injury.
The child now endures "many difficulties and impairments", the court heard.
The man was also taken to hospital after suffering serious injuries including a spinal fracture, broken arm and a brain injury.
Blood tests revealed he was affected by methamphetamine.
He was also found in possession of a large machete.
The man did not have a licence after being disqualified from driving while the motorbike was unregistered and not insured.
Eleven days after the crash the man was aggressive toward hospital staff before discharging himself.
He hid at his sister's home where he was later found and charged.
Judge Smith said there was a significant amount of drugs in the man's system which directly contributed towards the collision.
"I find your dangerous operation was a substantial cause of this," said Judge Smith, who noted that the 4WD driver had also contributed to the injuries.
The man is very remorseful, offering a written apology, and wants to stay drug-free, the court heard.
The man's parents separated when he was two and he endured a difficult stepfather while his mother was an alcoholic, the court heard.
Diagnosed with ADHD and learning difficulties, he first used cannabis at 15, alcohol at 17 and meth at 22.
The man, who has a lengthy criminal and traffic history, pleaded guilty to charges including dangerous operation of a vehicle causing grievous bodily harm while adversely affected by an intoxicating substance.
He was sentenced to five-and-a-half years in jail and will be eligible for parole in February 2024.
The man was also disqualified from driving for five years.
