DENVER (Reuters) - A Colorado DJ accused of groping recording star Taylor Swift during a photo shoot four years ago testified on Tuesday that he innocently made physical contact with the singer as they posed together but denied any inappropriate behavior.

Taking the witness stand on the first day of testimony at the federal court trial of their dueling lawsuits, Denver radio personality David Mueller said Swift’s allegations, which he emphatically denied, “cost me my career, my passion, my income.”

Mueller, 55, who was fired from his $150,000-a-year job at radio station KYGO-FM over Swift’s accusations, insisted that the case he brought against Swift was about more than just the loss of his livelihood and money.

“I want to clear my name,” he said. “It’s a humiliating experience to be accused of something so despicable.”

The U.S. District Court jury is weighing Mueller’s false-accusation claim against Swift’s cross complaint alleging assault and battery. The two cases were merged for trial.

According to Swift, Mueller slipped his hand under her dress and grabbed her bare buttocks as the two posed, along with Mueller’s girlfriend, during a meet-and-greet session before a June 2013 concert in Denver.

“It was not an accident, it was completely intentional, and I have never been so sure of anything in my life,” Swift, 27, said in a deposition.

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Expected to take the witness stand herself later in the trial, Swift listened intently to Mueller’s testimony, resting her chin in her hand. Her mother, Andrea, seated beside her, teared up at an early mention of the alleged groping incident.

Under questioning from his lawyer, Mueller recounted he may have made contact with the side of Swift’s body or brushed her arm and hand while they posed for pictures, but when asked if he had grabbed her backside, Mueller said flatly, “No, I did not.”

Mueller testified he had no inkling anything was amiss until approached that evening by a member of Swift’s security team who related her allegation to him, threatened to call the police and then told Mueller he was banned from all future Swift concerts.

The litigation was initiated by Mueller, who claims Swift fabricated the groping story and pressured station management to oust him from his job. His lawsuit seeks lost earnings.

Swift, who was in court and is expected to testify later in the trial, countersued asking for monetary damages of just $1. Swift has asserted that her representatives informed KYGO management about the incident but that she never demanded Mueller be fired.

In his opening statement on Tuesday, Swift’s lawyer, J. Douglas Baldridge, said Mueller committed an assault on his client and was now targeting her for money and fame, telling the jury, “He wants to make the victim pay the price.”

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He later grilled Mueller aggressively under cross-examination, noting that the DJ did not sue his former bosses or the radio station over his dismissal.

Mueller’s attorney, Gabriel McFarland, opened his case by showing the eight-member jury a picture from the photo shoot in question and said his client’s hand was not under Swift’s skirt.

“Let’s be clear, inappropriate touching is offensive. It’s wrong and it should not be tolerated .... Falsely accusing is equally offensive and it’s equally wrong,” he said.

Swift, one of the most successful contemporary music artists, earned $170 million between June 2015 and June 2016, following a world tour and her best-selling “1989” album, Forbes Magazine said.