A Toronto police constable has been charged by Ontario's Special Investigations Unit in connection with an extensive probe into the arrest of a man whose arm was broken during last summer's G20 summit.

Const. Glenn Weddell was charged on Friday with assault causing bodily harm, almost one year after the alleged incident took place.

Dorian Barton, 29, claimed his arm was broken when he was assaulted by police during a demonstration in downtown Toronto on June 26, 2010.

Civilian witnesses have told the SIU that Barton was taking pictures of mounted police officers when he was struck with a riot shield and hit with a baton or batons while lying on the ground.

"They hit me with a riot shield, slammed me to the ground, stepped over me and then started dragging me," Barton told CTV Toronto on Friday.

With his face bruised and arm broken, Barton was hauled off to a temporary jail, where he remained overnight.

SIU Director Ian Scott said Friday that there were reasonable grounds to believe the Toronto police officer committed a criminal offence during the arrest.

The investigation into Barton's injuries has faced several roadblocks over the past several months and was twice closed without charges being laid.

It was first closed on Nov. 25 but re-opened two months later after seven photographs of Barton's arrest surfaced.

Eleven police officers who had been identified at the scene were interviewed by the SIU, but none could identify the perpetrator of the strikes against Barton. The investigation was closed again on May 16.

The investigation was again re-opened 10 days later when Scott demanded the Toronto Police Service turn over information about the method they used to identify officers in the Barton incident.

The SIU says Toronto police have since turned over that information, leading to the charge.

"On the basis of information received in those interviews, and in conjunction with information gathered in the prior investigations, there are now reasonable grounds to believe that Toronto Police Constable Glenn Weddell committed the offence of assault causing bodily harm against Dorian Barton on June 26, 2010," Scott said in a statement.

Weddell is required to appear in court on July 21.

The SIU is an arm's length agency that investigates reports involving police where there has been death, serious injury or allegations of sexual assault.

Weddell is now the second police officer to be charged in connection to the violence surrounding the G20 summit.

Const. Babak Andalib-Goortani faces charges stemming from two separate attacks on June 26, 2010.

With a report from CTV Toronto's Austin Delaney