A Williams Lake RCMP officer who punched a First Nations teen in the face has been acquitted of an assault charge.

On Monday, the judge ruled Const. Andy Yung acted reasonably during the arrest of 18-year-old Jamie Haller in 2011.

Haller's mother, Martina Jeff, was expecting a different result.

"It's been a hard, long, year and a half. We thought we were going to get justice. And everything just didn't go the way we thought it was going to go. It affected Jamie, it took a lot out of her," Jeff said.

During the trial, Yung admitted that he punched Haller in the face while she was handcuffed in the back seat of his police cruiser, but said he did so because she was drunk and agitated and had wrapped her legs around his head.

Haller testified that the officer punched her more than six times, but the judge found her testimony to be inconsistent and evasive.

"What means most to me at the end of the day here is that the judge, in his careful deliberation, chose to accept the evidence of constable Yung," said Insp. Warren Brown, head of the Williams Lake RCMP detachment.

"And that tells me that the evidence provided by Const. Yung was truthful, and regardless of the decision, that would be my biggest concern."

Yung has been on desk-duty since the charges were laid.

Brown says it is too soon to say whether or not the RCMP will conduct an internal review, or if Yung will return to active duty in Williams Lake.

Const. Yung has been in trouble before.

In 2008, while providing security at an international summit in Banff, he was involved in a drunken telephone conversation with his ex-girlfriend when he fired his service gun into the ceiling of his hotel room.

Yung was later cited for disgraceful conduct and docked five days pay.