A Toronto police sergeant has been charged with the sexual assault of a 27-year-old woman in September 2015 following an investigation by Ontario's Special Investigations Unit (SIU).

The SIU alleges that Sgt. Christopher Heard encountered the woman near Wellington Street and Blue Jays Way around 1 a.m. on Sept. 24 and subsequently drove her home in his police cruiser.

On the way to her residence, the SIU alleges that Heard sexually assaulted the woman in the police car.

Heard, who has been a Toronto police officer for more than 20 years, is a father of three. In 2012, he was a member of the police's mounted unit. He also won an award for his role in an off-duty water rescue at Sharbot Lake Provincial Park.

He faces one charge of sexual assault. He is due to appear in court at Old City Hall on April 14.

For now, Heard will be suspended from the police force with pay, which is required under the province's Police Services Act.

'We take conduct seriously,' police chief says

Chief Mark Saunders said he's concerned about any incident that erodes public trust in police.

"We take conduct seriously," Saunders told CBC News.

"When we do see misconduct we take appropriate action."

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