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A local litigator logged a win in La-La-Land on Monday, convincing a federal jury that Katy Perry's "Dark Horse" improperly copied a 2009 Christian rap song by a St. Louis artist.

Michael A. Kahn of the Capes Sokol law firm in Clayton represented Marcus Gray — who performs under the stage name "Flame" — and other co-authors. They alleged that Perry's 2013 hit stole from their song "Joyful Noise," the Associated Press reported.

Gray and one co-author, Chike Ojukwu, are from St. Louis.

Now the arguments switch to determining how much money Perry and the other defendants will owe for copyright infringement.

Perry's song spent four weeks atop the Billboard Hot 100 in early 2014, and earned her a Grammy nomination.

Perry and her song's co-authors testified they never had heard the song, or of Gray, before the lawsuit was filed in 2014. They also said they did not listen to Christian music, the AP report said.