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 Combs' ex-girlfriend Cassie Ventura has taken the stand to testify in the trial against the music mogul. After male escort Daniel Phillip told the jury Monday that he saw “Sean Combs hit Cassie,” a defense attorney today questioned whether he embellished the account to make Combs seem more callous.