Lukasz “Dr. Luke” Gottwald’s legal team has subpoenaed pop singer Lady Gaga as part of the songwriter/producer’s defamation suit against his former protege, Kesha. It’s the latest development in the ongoing legal battle between the two parties; Kesha originally filed a lawsuit accusing Gottwald of physical and sexual abuse in 2014.

A statement released by Gottwald’s rep says, “In connection with Dr. Luke’s defamation claims against Kesha, various third parties are being deposed by both sides, including celebrities.”

It continues, “Dr. Luke’s counsel served a subpoena on Lady Gaga because she has relevant information regarding, among other things, false statements about Dr. Luke made to her by Kesha. This motion has become necessary because Dr. Luke’s counsel has not been able to obtain, despite repeated request[s], a deposition date from Lady Gaga.”

According to court documents obtained by TMZ, the subpoena request refers to a text message conversation between Kesha and Gaga in February 2016. The filing alleges the texts, which were entered into evidence by Kesha in December 2016, included statements by the pop singer about her abuse and implored Gaga to join a “smear campaign against [Dr. Luke].” Gottwald claims the campaign involved Gaga urging Sony Music to cut ties with him, and promoting “Free Kesha” on social media.

Gottwald’s lawyers claim the copy of the texts they previously received via subpoena were “heavily redacted” and “incomprehensible.” Gaga has offered to provide a written statement, but the lawyers prefer to question the singer during a three-hour deposition regarding the full contents of the text conversation.

Amidst the ongoing legal battle, Kesha is preparing the release of a new album, Rainbow, out August 11th through Kemosabe Records/RCA Records. In April, Gottwald was reportedly removed as CEO of Kemosabe, the imprint he founded under Sony in November 2011.