He was terminated from his position on June 4, 2013, two days after the alleged incident with Swift.
Mueller is suing Swift for $3 million for losing his job.
Swift and Mueller are both expected to testify, along with Mueller's former boss and members of Swift's entourage.
Swift appeared in court in a white dress and black jacket, even though she and Mueller were not required to attend until the actual trial begins.
He claims he was sacked after Swift falsely accused him of grabbing her and he is seeking up to $3 million in damages.
According to TMZ, 32 seats will be open to the public for those interested in the trial (the case has predictably drummed up plenty of buzz among Swift's fans and locals).
Could Taylor Swift lose her case? Swift in a way she found inappropriate, it was inadvertent as he rushed to get into position for the photograph, which, though inconclusive, is expected to be key evidence at the trial.
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As part of her counter claim, Swift requested a jury trial for the matter, and offered to donate any winnings from the suit to "charitable organizations dedicated to protecting women from similar acts of sexual assault and personal disregard".
Taylor Swift is in federal court in Denver for the start of jury selection in her lawsuit against Denver disc jockey David Mueller involving a groping allegation.
Mueller's attorney, Gabriel McFarland, argues that Mueller may have been misidentified after someone else touched Swift.
"It was not an accident, it was completely intentional, and I have never been so sure of anything in my life", Swift said in a deposition.
Mueller was sacked on June 4th, 2013 after Swift's team gave the photo to the radio station.
Immediately after the meet-and-greet, Swift says, she confirmed the assault with a photographer and security staff, who then confronted Mueller.
Swift and her mother Andrea will both take to the stand during the trial, as will Mueller and Shannon Melcher - his co-host on the day of the alleged assault and his girlfriend at the time.
Mr. Mueller, who is scheduled to testify, has repeatedly denied groping Ms. It's not often you see a person of Swift's stature in the courtroom, let alone testifying, so the whole thing is being turned into quite a disturbing spectacle.