Explainer: Why pop star Taylor Swift will be sitting in court this week.

There could be a very valid explanation for why singer Taylor Swift has been missing in action from Instagram for most of this year.

The 27-year-old singer is currently focused on a civil lawsuit between her and a Colorado radio host, which began in Denver this week.

KYGO-FM host David Mueller was fired from his job at the radio station after Swift alleged he touched her inappropriately at a 2013 meet-and-greet.

The pair were posing for a photo together, when the 55-year-old allegedly “lifted her skirt and groped her”.

The singer had Mueller removed from the concert immediately, and alerted his employer. He was fired two days later.

LISTEN: Taylor Swift had the best response to sexual harassment and it gives us hope.

The radio host is now suing the star, her mother and his former employer, claiming he was “falsely accused”. He is seeking AU$3.8 million in damages.

Swift is counter-suing for assault and battery, and the two cases were merged for trial. During initial court hearings, she requested the photo evidence of the assault be sealed until the trial began, but it was leaked online in November 2016.

Taylor Swift — The ‘Sexual Assault’ Photo I Wanted to Keep Secret (PHOTO) https://t.co/qT5FRZLo4T

— TMZ (@TMZ) November 12, 2016

Jury selection for the trial – which begins today and is expected to last two weeks – took place on Monday, with US District Judge William Martinez and lawyers for the two parties quizzing members of the jury pool to detect any bias.

Potential jurors were asked for example, if they were fans of Swift or regular listeners of KYGO-FM.

Swift was present for the selection of the eight-panel jury, facing prospective jurors when introduced by the judge and taking notes during the selection process.

It’s expected she will take the stand to testify during the trial.

In a deposition, Swift said she was sure the alleged incident was "not an accident".

"It was completely intentional, and I have never been so sure of anything in my life," she said.

She claimed Mueller "grabbed onto my ass cheek and no matter how much I scooted over it was still there".

"I was barely able to get words out, and it was like somebody switched the lights off in my personality."

Swift's mother, Andrea, also wrote in the deposition about the impact the reported assault had on her daughter.

"I felt like I wanted to cry and throw up at the same time," she said.

"She was upset. She cried. We cried. It was - it was just inconceivable."

The singer has vowed to donate any potential monetary awards from the trial will be donated to organisations "dedicated to protecting women from similar acts of sexual assault and personal disregard."

- With AAP

If you or someone you know is in need of help, please call the National Sexual Assault, Domestic and Family Violence Counselling Service on 1800 RESPECT.