DENVER (Reuters) – Singer-songwriter Taylor Swift, known for baring her soul and her grudges in her music, presented an unflinching account under oath and in open court of her allegation that a Colorado DJ groped her while they posed for photos together four years ago.

The 27-year-old Grammy-winning artist behind such hits as “Fearless,” “Bad Blood” and “I Knew You Were Trouble,” took the witness stand on Thursday on the fourth day of a federal court trial in Denver pitting her against the man she has accused of sexual assault, David Mueller.

The eight-member U.S. District Court jury is weighing her charge that Mueller clutched 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.

But with the exception of Mueller, the trial’s first witness, almost every individual subsequently put on the stand by his attorney, Gabriel McFarland, delivered extremely compelling testimony in support of Swift’s case.

Swift’s testimony was so apparently devastating to Mueller that her lawyer, D. Douglas Baldridge, declined a chance to cross-examine his own client when McFarland was done questioning her. It remained to be seen whether Baldridge would call anyone else to the stand once McFarland rests his case.

In unvarnished language that occasionally drew titters in the courtroom, even from some jurors, Swift said she was subjected to a “very long” and “intentional” grope by Mueller as they posed for a photo with his girlfriend, and that he appeared to be drunk at the time.

“Your client grabbed my ass,” she told McFarland. “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.”

The photograph in question, 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.

Swift 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 testimony from several others, including her photographer, Stephanie Simbeck, who recalled seeing through her camera’s viewfinder Mueller “put his hand on (Swift’s) butt.” 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.

In emotional testimony on Wednesday, Swift’s mother, Andrea, pointed her finger at Mueller from the witness stand, saying, “He sexually assaulted my daughter, right there, that guy.”

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.

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