Who is Cassie? Casandra Ventura is the R&B singer and actor who started testifying Tuesday in Sean “Diddy” Combs sex trafficking trial. She is known simply as Cassie.

Sean "Diddy" Combs used fame and violence to sexually abuse women, prosecutors have said in opening statements at the hip-hop mogul's trial, while the rapper's attorneys defended his "swinger" lifestyle. The 55-year-old has pleaded not guilty to charges including racketeering, sex trafficking and transportation to engage in prostitution.

Sean "Diddy" Combs' ex-girlfriend Casandra Ventura, a rhythm and blues singer known as "Cassie," is expected to testify on Tuesday as the prosecution's star witness in the hip-hop mogul's sex trafficking case,