By Lisa Respers France, CNN

(CNN) -- Taylor Swift has been pretty quiet lately, but she will soon speak out about an alleged sexual assault.

The superstar singer is expected to testify in a civil case filed by a Denver disc jokey who claims he lost his job after Swift accused him of groping her backstage at one of her concerts in 2013.

According to pre-trial legal documents obtained by CNN, David Mueller, who was known professionally as "Jackson," maintains that Swift and co-defendents, including her mother Andrea Swift, falsely accused him of improperly touching her during a meet-and-greet that he attended for his then employer, KYGO radio.

Swift, who was 23 at the time, claims in a legal response to Mueller's suit that he assaulted her when they posed for a photo by "reaching under her dress and grabbing her bottom."

Swift says she told her mother and members of her team what she says happened, but denies that she complained to Mueller's employer, as he asserts in his claim.

Rather it was her radio promotions director, Frank Bell, who alerted KYGO to the alleged incident. The station conducted an investigation and moved to terminate Mueller, Swift's filing states.

"No less than seven KYGO personnel participated in the investigation," Swift's pre-trial response states.

According to Swift's response, "KYGO fired Mueller for violating the morality clause of his contract after it independently determined that he had lied about the incident, changed his story, and inappropriately touched Ms. Swift. Mueller never sued KYGO for breach of his employment contract."

Mueller said in his complaint that Bell contacted KYGO's general manager Bob Call and told Call the station "could be gravely impacted" by the alleged incident. Mueller claims he was fired after Call was told Swift and her parents were "looking for specific action" from the station.

Swift maintains she is "absolutely certain of what Mueller did "and is prepared to testify "that Mueller 'put his hand under [her] dress and grabbed [her] bare a.'"

Swift, Bell and Swift's mother are expected to testify on her behalf, as is Lorraine Bayard de Volo, chair and associate professor of women and gender studies at the University of Colorado, who will offer expert testimony on the conduct of and ramifications for victims of sexual assault and harassment.

Mueller first initiated his suit in 2015. Swift filed a counterclaim against him for allegedly groping her.

In May, a judge threw out Mueller's claims of slander against Swift. Mueller was also sanctioned for destroying electronic devices that contained evidence in the case.

CNN has reached out to Swift's representatives for additional comment on this story. They have not yet responded.

Trial is scheduled to begin in Denver on August 7.