A Calgary police officer on trial for assaulting his pregnant common-law wife was found not guilty on all charges Friday.

Mark McCullough, a nine-year member who is currently suspended from the Calgary Police Service with pay, was facing three counts of domestic assault.

Provincial court Judge John Holmes said the Crown failed to prove guilt beyond a reasonable doubt.

A trial held in September revealed McCullough, 44, and the alleged victim — his ex-fiancee — had different versions of the incidents that transpired in November 2016.

The former couple were the only two people to testify in the he-said-she-said trial. Both parties agreed they fought a lot over the course of their three-year relationship.

The woman, who CBC News is not naming to protect the children involved, was eight-months pregnant at the time of the incidents. She told the court that McCullough twice assaulted her during arguments nine days apart. But McCullough said his ex initiated the violence — punching him and head-butting him.

'Finally put the matter behind him'

McCullough's defence lawyer, Cory Wilson, said he never had a doubt his client would be acquitted of the charges.

"Mr. McCullough was a victim of domestic violence and at all times acted in self-defense. He is overwhelmed with emotion and is grateful that he can finally put this matter behind him," Wilson said in an email statement to CBC News.

​McCullough is also facing unrelated charges of breach of trust and obstruction of justice, accused of helping a friend avoid an impaired driving charge in 2015. A trial date for those charges has not yet been set.