A Western Australian police officer who grabbed a woman on the bottom at a sporting event in the state's north-west has been found not guilty of indecent assault by a magistrate who described the incident as "low on seriousness".

Andrew John Ramsden, 48, has been standing trial in South Hedland Magistrates Court on a charge of indecent and unlawful assault following an incident at a charity wheelchair basketball match at Wanangkura Stadium in December.

In finding Sergeant Ramsden not guilty, Magistrate Michelle Ridley said in 2017 there was more touching between males and females than ever before.

"(In) the era of twerking, grinding and easy access to pornography, something like pinching someone on the bottom seems to have lost its overtly sexual connotation," Magistrate Ridley said.

"It seems it's low on seriousness now, that it doesn't even rate a mention."

Sergeant Ramsden, who was stood down while the court matter was dealt with, appeared relieved as Magistrate Ridley delivered her verdict.

Earlier, the South Hedland Magistrates Court heard the incident occurred during a team photo when the police officer was standing behind the woman, who cannot be named for legal reasons.

Sergeant Ramsden had taken part in a charity fundraiser for a teenager diagnosed with a terminal illness.

The court heard he grabbed the woman's bottom as the team posed for a photo after the game.

The woman had instructed the players to look "tough" for the photo.

The court heard he had stood behind the woman and said to her "I hope you take this the right way" and grabbed her, causing her to jump forward.

"I didn't particularly want a serious photo as that's not in the spirit of the day," Sergeant Ramsden told the court.

The incident happened at South Hedland's Wanangkura Stadium at a charity wheelchair basketball match in December 2017. ( ABC North West WA: Kendall O'Connor )

"I thought let's turn this into a funny photo.

"I wanted a reaction for the photo, unfortunately that reaction wasn't what I was expecting."

Sergeant Ramsden told the court he had made a serious misjudgement.

The woman said she felt "shocked" and "humiliated" after the incident.

"I was struggling to process it … I started saying under my breath 'that's not okay'," she told the court via video link.

She said she confronted him but felt he had not taken her complaint seriously.

Defence lawyer Linda Black told the court Sergeant Ramsden had only touched the woman on her side, or "love-handle area", and had apologised twice after seeing her reaction.

South Hedland Police officer in charge, Senior Sergeant Allan Jane, told the court he was shocked by what had happened.

He described Sergeant Ramsden as an outstanding officer and had never received any complaints about him or his behaviour with women.

Sergeant Ramsden had been a police officer for 17 years, the court heard.

After the verdict, a WA Police Force spokesperson released a statement to the ABC saying the officer remains stood down from operational duties and the merits of an appeal will be considered.

"Independent of today's court outcome, there is a separate police internal investigation underway into the officer's conduct," the spokesperson said on Thursday.