The 55-year-old hip-hop mogul has been charged by federal prosecutors with sex trafficking, racketeering conspiracy and transportation to engage in prostitution.

Kid Cudi, whose real name is Scott Mescudi, was called as a witness by the prosecution. Mescudi, the "Pursuit of Happiness" rapper, was once in a brief relationship with Combs' ex, Casandra "Cassie" Ventura .

Kid Cudi took to the witness stand on Thursday to testify at Sean 'Diddy' Combs' sex-trafficking trial. Cassie alleged that Diddy reacted violently when she and Kid Cudi had a fling in 2011.