DENVER (Reuters) - Grammy-winning singer-songwriter Taylor Swift testified on Thursday she was subjected to a “very long” and “intentional” grope by a Colorado disc jockey who appeared to be drunk during a photo session four years ago.

A sketch of Taylor Swift (L) and her attorneys in Denver Federal Court with plaintiff David Mueller (2nd R) during the Swift groping trial in Denver U.S. August 8, 2017. REUTERS/Jeff Kandyba

The 27-year-old pop star was testifying for the first time for a U.S. District Court jury weighing her accusation that David Mueller grabbed her bare buttocks during a pre-concert fan reception in 2013 against Mueller’s assertion that she falsely accused him and then got him fired.

Swift - one of America’s most successful recording artists, whose hits include “Fearless” and “Fifteen” - spoke forcefully under questioning by Mueller’s attorney, Gabriel McFarland. She said several times, “Your client grabbed my ass,” at one point calling it a “devious and sneaky act.”

“It was a definite grab ... a very long grab,” she said. “It was intentional. He stayed latched onto my bare ass cheek. I felt him grab onto my ass cheek under my skirt.”

Mueller, 55, testified on Tuesday that he may have made innocent contact with Swift but denied any inappropriate behavior. Asked if he grabbed her backside, the former disc jockey for Denver radio station KYGO-FM replied, “No, I did not.”

Swift spent an hour on the witness stand on Thursday and said it appeared both Mueller and his girlfriend, who stood on the other side of her for the photo, had “had a few cocktails.”

The photograph, repeatedly displayed in court, shows the pop star in a black skirt and top, flanked by Mueller and his girlfriend, all three smiling for the camera. Mueller has his right hand concealed behind her rear end, and Swift appears to have shifted her hip slightly away from him.

Asked by McFarland why her bodyguard did not step in when “this big drunk guy” groped her, Swift replied: “No one could have expected this to happen. ... It had never happened before. It was horrifying and shocking.”

‘THAT’S HIM’

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Swift also sharply denied McFarland’s suggestion that Mueller was the victim of mistaken identity. “He had a handful of my ass. I know it was him,” she fired back.

Swift’s account was backed by subsequent testimony from her photographer, Stephanie Simbeck, who recalled seeing Mueller “put his hand on (Swift’s) butt” through the camera’s viewfinder. She said it was clear to her that Swift “was trying to get away” from Mueller.

Once he and his girlfriend left, Simbeck testified, Swift said aloud: “Dude, that guy grabbed my ass,” to which Simbeck responded, “I knew it. I have the photograph.”

They quickly found the Mueller image in her camera, and Swift said, “That’s him,” Simbeck told jurors.

Explaining why she did not report the incident to her managers and security detail right away, Swift said she still had more fans to meet and “didn’t want to ruin their concert experience.”

Questioned about her reaction to learning Mueller had been fired, Swift replied, “I just never wanted to see him again. And here we are years later, and I’m being blamed for the unfortunate events in his life.”

Mueller initiated the litigation, claiming Swift fabricated the story and put pressure on KYGO to fire him from his $150,000-a-year job. Swift then countersued for assault and battery, asking for symbolic damages of $1. Swift asserts she never demanded Mueller be fired.

The former DJ is seeking lost earnings and to clear his name, telling the court this week that it was humiliating to be accused of “something so despicable.”

Following Swift to the witness stand was KYGO manager Robert Call, who fired Mueller two days after the alleged incident, acting on a complaint from Swift’s liaison to radio stations, Frank Bell. Call testified that he had known Bell for many years and had no reason to doubt him.

Call said Mueller at first denied to him that he had touched Swift at all. But when shown the photo in question, Call said, Mueller responded: “Well, if it did happen, it was accidental.”

Call said he fired the DJ because of his shifting accounts of the incident, and because the photo showed that Mueller’s hand was “not where it was supposed to be.”

Swift, who has 85 million followers on Twitter and 102 million followers on Instagram, earned $170 million in the year to June 2016 following a world tour and her best-selling “1989” album, according to Forbes Magazine.