The 'Praying' hitmaker sued the music producer - whose real name is Lukasz Gottwald - in 2014 in a bid to get out of her recording contracts as she accused him of sexual assault and battery, and he subsequently filed a countersuit for defamation.
And a judge has now ruled Luke was defamed when Kesha made a ''false statement'' in the message to the 'Poker Face' hitmaker by claiming he had raped Katy Perry.
Court documents obtained by E! News said: ''Perry unequivocally testified that Gottwald did not do so. In response, Kesha has not raised a triable issue. There is no evidence whatsoever that Gottwald raped Katy Perry or that Katy Perry, whose sworn testimony is unrefuted, must not be believed.''
The judge ruled Luke is not a public figure or a ''household name'' and so did not to prove at trial that Kesha was acting with ''malice'' when she made the rape accusation.
The judge explained: ''Gottwald certainly is not a 'general public figure.
''Although he may be well known in music-industry circles, he has never been a household name or achieved general pervasive fame and notoriety in the community. Nor is he a limited-purpose public figure.''
The 32-year-old star was also ordered to pay $373,671.88 in interest on a royalty payment of more than $1.3 million that she made to the producer's label KMI in August 2017, which was ''well beyond the deadlines set forth in the parties' contract''.
The ruling stated: ''Kesha does not dispute the terms of the contract or the calculation of the interest.''
The defamation case will now go to trial.
The judge said: ''Ordinarily, statements made during or in connection with good-faith anticipated litigation are privileged and cannot give rise to defamation liability.
''Here, however, there are sharply disputed questions of fact going to the heart of the case about whether Kesha's California complaint was brought in good faith, as Kesha asserts, or whether it was a 'sham' intended to defame and pressure plaintiffs, as plaintiffs assert.''
Kesha has vowed to appeal the rulings.
Her legal team said in a statement: ''Judge Schecter issued rulings today on motions for summary judgment in the Dr. Luke litigation. We disagree with the Court's rulings. We plan to immediately appeal.''
Meanwhile, Luke was delighted with the rulings and ''looks forward'' to the trial taking place.
He said in a statement through his lawyer: ''Today's important decision by the Court in Dr. Luke's lawsuit brings him closer to the justice that he seeks.
''First, the Court has now ruled that Kesha made a false and defamatory accusation about Dr. Luke when she baselessly claimed that he raped Katy Perry.
''Second, the Court rejected Kesha's attempts to invoke legal technicalities to avoid responsibility for her statements. And third, the Court also correctly held that Kesha breached her contract with Dr. Luke's company.
''Dr. Luke looks forward to the trial of his case where he will prove that Kesha's other false statements about him were equally false and defamatory.''
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