Mr Mueller's hand, unseen in the picture, was allegedly placed inappropriately low behind Ms Swift's back.
Taylor Swift, 26, has accused Mr Mueller of sexual assault. Last month, she was granted the right to keep the photograph out of public view on the grounds that it might prejudice the jury, reported E!Online. However, she was not allowed to keep other evidence secret.
A transcript of the Bad Blood singer's deposition from July was obtained by E!Online. In it, Ms Swift recalls, "Right as the moment came for us to pose for the photo, he took his hand and put it up my dress and grabbed onto my a** cheek and no matter how much I scooted over, it was still there. It was completely intentional, I've never been so sure of anything in my life."
Taylor Swift said she remembered "feeling violated in a way I had never experienced before" and was "stunned" at the situation.
Her security guard Greg Dent corroborated what allegedly occurred between Ms Swift and the DJ.
Mr Mueller says he is innocent and is suing the singer, claiming he was fired from his job over "false accusations" that he groped her.
Taylor Swift filed a counter suit against David Mueller for assault and battery.
The Grammy winner has reportedly demanded a jury trial and promised that any money won from the trial will benefit charitable organisations "protecting women from similar acts of sexual assault and personal disregard."