With Taylor Swift and her mother, Andrea Swift, present, Mueller told the jury, which is comprised of six women and two men, that he was fired from his job even after he was "100 percent clear" with his managers that he did not grope the pop star.
He also claimed that he recorded the meeting during which he was let go, but said that the audio was destroyed when he accidentally spilled coffee on his computer.
The reason he sued Taylor Swift, he said, was to clear his name.
"It's a humiliating experience to be accused of something despicable," he told the jury.
Mueller sued Taylor Swift first in 2015, claiming that the singer had falsely accused him of grabbing her backside during the event, and that her allegation caused him to lose his job. According to his suit, Mueller is accusing Swift of "intentional interference with contractual obligations" and "interference with prospective business relations" that led to lost wages.
Taylor Swift, who is also expected to testify, claimed in a countersuit obtained by ABC News that Mueller "took his hand and put it up my dress" during the publicity event, and it "was not an accident." Mueller denied "unequivocally" that he intentionally groped the singer, according to the documents.
During cross-examination, Taylor Swift's attorney Doug Baldridge noted that Mueller did not sue the radio station, and repeatedly said that "the jury will never know" what transpired during his meeting with his KYGO bosses. He also asked Mueller for a reason why Taylor Swift would make up her story, to which the former DJ responded, "I cannot."
While Mueller said in depositions that his damages amount to some $3 million, Taylor Swift wants compensatory, actual and punitive damages in an amount to be proven at trial, but also a verdict that holds Mueller responsible for the alleged assault.
Taylor Swift says she will donate any money she receives to charities.