Taylor Swift has won long-awaited vindication after a jury decided that a radio host groped her during a pre-concert photo op four years ago.

After a weeklong trial over duelling lawsuits, jurors determined Monday that fired Denver DJ David Mueller assaulted the pop star by grabbing her backside during a backstage meet-and-greet.

In a statement, Swift thanked her attorneys "for fighting for me and anyone who feels silenced by a sexual assault."

She added: "My hope is to help those whose voices should also be heard" and pledged to make unspecified donations to groups that help victims of sexual assault.

The six-woman, two-man jury also found that Swift's mother and radio liaison were within their rights to contact Mueller's bosses.

Mueller sued the Swifts and their radio handler, Frank Bell, seeking up to $3 million US for his ruined career.

Just before closing arguments, the judge dismissed Swift from Mueller's lawsuit and drastically reduced the amount Mueller could collect.

The singer-songwriter said in her countersuit that she wanted a symbolic $1 and the chance to stand up for other women.

Photographic evidence disputed

During closing arguments in federal court, Mueller's attorney questioned why Swift was smiling in a pre-concert photo taken when she said Mueller reached under her dress and grabbed her backside.

"Look at Ms. Swift's face. Is that the face of someone who's in shock, who is upset?" Gabriel McFarland said while showing the photograph of Mueller and Swift at a backstage event.

Swift, who testified forcefully last week, cried and wiped her face as her mother touched her right leg. Andrea Swift touched her daughter's hand as McFarland said the photograph meant nothing.

When the attorney suggested that Swift would not have kept her arm over Mueller's if he had grabbed her backside, Swift silently mouthed "wow."

Swift's lawyer also pointed to Mueller's expression in the photo as proof. Without using the expletive, lawyer Douglas Baldridge said, "That is an S-eating smile right there."

The photo was shown several times to jurors but has been sealed by the court.

Mueller denies touching the pop star.

Taylor Swift Radio Host

In this courtroom sketch, pop singer Taylor Swift speaks from the witness stand during the trial on Thursday. (Jeff Kandyba/Associated Press)

U.S. District Judge William Martinez dismissed the claim against Swift on Friday, saying Mueller did not present enough evidence. The six-woman, two-man jury is still considering the claims against Andrea Swift and Bell.

The judge also said the former DJ is only entitled to two years' worth of earnings — about $300,000 — if jurors side with him.

'The guy did it. Don't be fooled'

The singer's lawyer said during a closing argument that Mueller lost audio recordings he secretly took during a meeting with his bosses shortly after he was fired. Baldridge accused Mueller of changing his story and noted that his side never disclosed what the lost evidence was at trial.

"The guy did it. Don't be fooled," he told jurors.

McFarland told jurors that Swift's account of what happened is inconsistent with the testimony of every other member of her team. He also said Mueller immediately asked someone to call the police when he was confronted by security guards.

Taylor Swift Radio Host

Borrowing a line from one of her songs, workers put up a sign in support of pop singer Taylor Swift in the window of an office building across the street from the federal courthouse in Denver. (David Zalubowski/Associated Press)

"That's not the type of guy who grabs or gropes a superstar, apparently out of the blue," he said.

He also cast doubt on the claim of former Swift security guard Greg Dent that he saw Mueller touch Swift while the photo was shot but did not act because he did not think she was in danger.

McFarland said the photographer who took the image, Stephanie Simbeck, "started it all" by pulling the photo of Mueller, his then girlfriend and Swift from dozens taken at the event and showing it to Swift, who identified Mueller as the person who touched her.

Baldridge told jurors that Swift is standing up for all women and saying, "No means no."

He characterized Mueller as an aggressor and asked jurors: "Will aggressors like David Mueller be allowed to victimize their victims?"