Even after taking the "very rare" step of reopening a closed investigation to consider more evidence, the director of Ontario's police watchdog has concluded a man who fell from a second-storey apartment in Hamilton was injured without police being at fault.

The incident happened just after midnight one night in September 2016.

Police got a call about a fight between a man and a woman in a Hamilton apartment. Two officers were dispatched.

'His version of events changed dramatically.' - SIU report

When one officer arrived, he tried to speak with the man, but he went back into the house, climbed through an upstairs window and tried to run away across the roofs of adjacent buildings, according to a report on the incident from Ontario's Special Investigations Unit.

He fell and was arrested. One officer deployed his conducted energy weapon (commonly known as Taser) twice.

The man was taken to hospital. He broke a rib in the fall.

The SIU announced two weeks later it had opened an investigation.

When the man was interviewed by SIU, paramedics, medical personnel or corrections officers, he didn't allege anything about an officer hitting him.

And he didn't say "that his sore left rib and head were caused by anything other than his fall from the roof when he landed on a pipe," the report states.

As a result of his account and the evidence collected, the SIU notified the man that his file was closed due to the finding that "his injury had occurred as a result of his fall from the roof without any intervention by police."

But the man said he'd been charged with assaulting police and now wanted to change his statement and "tell the truth," according to the SIU.

So the SIU reopened its investigation in October 2016.

"The reopening of a closed investigation is very rare," said Monica Hudon, a spokeswoman for the SIU. That only happens when the director believes there is new information available that might "materially affect the outcome."

When the SIU interviewed the man again, "his version of events changed dramatically," the report states.

"The [man] changed his description of his own actions, the number of officers that deployed their [Tasers] at him, exponentially increased the number of officers who surrounded him just prior to his arrest, and alleged that he was threatened and punched in his left side ribs by an unknown officer," the report states.

But the SIU found this statement contradicted the physical evidence and the account of events the man had previously provided to police, paramedics, hospital staff and corrections staff at the Barton jail.

"I reject the second statement of the Complainant, because all of the items outlined above which confirm the first statement, contradict the second," SIU Director Tony LoParco wrote.

LoParco said the force used by officers to apprehend and subdue the man was justified.

"They used no more force than necessary to first apprehend a fleeing [man] who was running on the rooftops of people's homes and garages, and then to arrest him," he wrote.

LoParco concluded no charges are justified against the officers.