Ontario's Special Investigations Unit says there are no grounds to charge any Toronto police officers in the death of a young man near York University.
Junior Manon, 18, of Toronto died last May 5 following a foot chase by police after a traffic stop.
A post-mortem concluded the cause of death was "positional asphyxia following struggle and exertion."
The SIU says two officers stopped a car driven by Manon for a minor traffic offence, and when they tried to arrest him on a breach of probation, he broke free and ran.
The two officers chased Manon and eventually caught him and the three struggled on the ground before other officers arrived to assist.
The SIU determined that the exertion of running from police and pressure on Manon's chest during the struggle could have interfered with his breathing.
"Given the level of resistance from Mr. Manon ... I am of the view that the force used to arrest him was not excessive in these circumstances," said Ian Scott, director of the arm's-length agency.
The SIU said 26 officers were designated as witness officers and two as subject officers in the case. Eighteen civilian witnesses were interviewed.