Provincial court Judge Gordon Krinke made eight recommendations in his report, including better medical examinations for prisoners.
Court heard Morbe Buluk showed up acting out of sorts at his parents' house in February 2010, and they figured he was drunk or high on drugs.
They called police and, after the 18-year-old spit on one officer, he was taken to a cell.
Paramedics examined Buluk there but failed to look at his pupils or conduct a common test for brain injuries.
No one was aware that a couple hours earlier, Buluk had been punched in a parking lot and struck his head on the pavement.
Cell staff later noticed Buluk lying on the floor of his cell. His body was making jerking movements and white foam was coming from his mouth. He was rushed to hospital, where doctors determined he had an irreversible head injury.
He died later that day.
"A key piece of Buluk's history was missing. This was, of course, the fact that Buluk had been struck and fell unconscious to the ground, striking his head," Krinke wrote in the report.
"Had this piece of information been available, Buluk’s treatment and outcome would likely have been significantly different."
The judge recommended that in cases where there is an incomplete account of events before an arrest, police and paramedics err on the side of caution and take prisoners to hospital.
He said if medical assessments are done in cells, they should always include pupillary reflex examinations and the Glasgow Coma Scale tests for brain injuries.
If need be, prisoners should be moved to a safe environment for assessments and their restraint devices should be removed.
Buluk had a spit sock covering his face when paramedics examined at him. Krinke said it may have been a reason why they didn't test his pupils.