Police said the officer was on-duty at the time and he was suspended when they became aware of the incident.
Const. Jeffrey Hall will make a court appearance in Kitchener on May 2.
It’s the latest in a string of allegations of sexual assault against officers with Waterloo Regional Police.
Const. Eric Schnarr was charged following an alleged incident on Oct. 14 during an Oktoberfest event in Kitchener. Police said Schnarr, a six-year member of the service, was off-duty at the time.
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A 26-year member of the force was suspended following an alleged incident in 2010 that was reported to police last November.
Meanwhile, the SIU announced in February that since Jan. 1, they have launched four investigations into sexual assault allegations made against Waterloo Regional Police.
Two of the incidents allegedly occurred more than 20 years ago, including one in the early 1990s and the other in October 1994, SIU said.
The SIU is an arm’s length agency that investigates reports involving police where there has been death, serious injury or allegations of a sexual assault.