Dr. Luke's (aka Lukasz Gottwald) legal team just subpoenaed Lady Gaga. The subpoena comes as part of the producer's lawsuit against Kesha. Kesha has her own lawsuit against Dr. Luke for sexual assault. "In connection with Dr. Luke's defamation claims against Kesha, various third parties are being deposed by both sides, including celebrities," Dr. Luke's representative Mother Monster has been a vocal Kesha supporter in her legal battle against Dr. Luke. Dr. Luke responded to Kesha's sexual assault case with a defamation countersuit.