It took a jury just 30 minutes to acquit a 31-year-old Karratha man of sexually penetrating a woman without her consent, following a two-day trial in Western Australia.

Key points: A jury has found a Karratha man not guilty of sexual penetration without consent

A jury has found a Karratha man not guilty of sexual penetration without consent Another man had consensual sex with the complainant, before leaving to sleep in another house

Another man had consensual sex with the complainant, before leaving to sleep in another house More than 50 photos were tendered to the court, including screenshots of text messages

The man, who the ABC is choosing not to name, had no previous criminal record when he was charged following the incident in May 2018.

The Karratha District Court heard he was at the Evolution Lounge Bar nightclub with friends on a Friday night, including his housemate.

The woman, who cannot be named, told the court she recalled meeting the man's housemate and going back to his house in the early hours of Saturday morning.

There she said she had consensual sex in a swag in one of the rooms with this housemate, who she claimed to like.

Evolution night club in Karratha. ( Gian De Poloni )

The court heard the housemate left the house after the encounter to stay at a friend's place as he could not sleep because of the woman's snoring, leaving her in the swag in his room.

In text message exchanges tendered to the court, he then messaged the man at the centre of the case and said "get rid of the naked woman in my room plz".

The man responded with numerous texts, asking who the woman was and writing "that ugly?".

He argued he then got up to use the bathroom and went into his housemate's room where he knelt beside the woman, tapped her leg and introduced himself, before inviting her to his "warm bed".

Woman claimed to be tricked

The complainant told the court she remembered being cold in the swag, but said she was half asleep when she was asked if she wanted to sleep in a warmer bed.

"I remember I thought … [the housemate] had made a bed up for us," the court heard the woman recall.

However, while appearing in court via video link from a separate room, she explained her distress in the morning believing that the man on trial had misled her to think he was his housemate.

"I went into the next room to find my underwear clothes and bag and realised what had happened, that I had been tricked," she said.

"The other person was holding up my underwear and I started yelling 'who the f*** are you, where's [your housemate], I'm calling the police'.

The man said he was shocked at the reaction and said he believed she had consented to sex with him.

"I was a bit taken aback by it … I was in shock," he said.

"I was confused by it."

At issue: Consensual sex or mistaken identity

The woman left the house, took photographs of the exterior and immediately called police who began investigating.

The Karratha District Court jury took just 30 minutes to reach a verdict. ( ABC Pilbara: Susan Standen )

More than 50 photos were tendered to the court which included screenshots of the texts, as well as one video.

In his closing statements, Department of Public Prosecutions senior state prosecutor Nick Cogin said the complainant was interested in the man's housemate.

"They had consensual sex," he said.

"How was it she got out of the swag and into the bed without recognising someone different?

"I would say it was perfectly understandable, what incentive did she have to tell you differently?

"She said she thought she was going with [the housemate]."

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Unanimous verdict

Throughout the trial, many theories were discussed including; whether the woman had given consent based on the thought that she was with the housemate, and whether that legally made the man on trial liable if he did not know, or whether he knew and simply did not correct the misunderstanding.

The jury also heard that despite claims the man did not ejaculate during the sex, the penetration of the woman with any part of his body was the focus of the charge.

The jury was sent for deliberation at 4:30pm on Thursday, and returned after half-an-hour with the unanimous not-guilty verdict.

The man, who was supported by three people in the gallery including his housemate, wiped away tears as Judge Birmingham QC closed the case.