A US jury has concluded Katy Perry's 2013 hit Dark Horse infringed on the song Joyful Noise by Christian rap artist Marcus Gray, aka Flame.

The decision followed a week-long trial in Los Angeles civil court, which included an appearance by Perry herself, who testified for 35 minutes.

In her testimony, Perry said that co-writers Dr. Luke (Lukas Gottwald) and Cirkut (Henry Walter) brought her the song...