Why Sean Diddy Combs's trial hinges on ex-girlfriend Cassie's testimony

In a trial that is undoing the legacy of one of music's biggest moguls of the 2000s, the focus of the opening week of proceedings was not Sean "Diddy" Combs himself - but his ex-girlfriend.

R&B singer Cassandra "Cassie" Ventura took the witness stand for four days, describing in emotional details the years of beatings and drug-fuelled sex encounters with prostitutes that she alleges she endured at the hands of the rap superstar, who she dated for more than a decade.

But while her story clearly left an impression on those in the courtroom, which one onlooker described as an "aura of sadness", it is just one piece in the puzzle that prosecutors must present to prove that Mr Combs was not just an abuser, but a mastermind of a criminal, sexual enterprise.

On Tuesday, gasps erupted in a Manhattan overflow courtroom when prosecutors called Ms Ventura - their star witness - to the stand. All eyes were fixed on the eight-months pregnant singer, as she strolled past her ex-boyfriend, whom she had not seen in six years.

Ms Ventura was there to testify in the federal sex trafficking, racketeering and prostitution case against Mr Combs, whom she accuses of abusing her and coercing her into unwanted sex acts - so-called "freak-offs" - during their 11-and-a-half year relationship.

Mr Combs is charged with racketeering conspiracy, sex trafficking and transportation to engage in prostitution - all of which he has vehemently denied.

Surrounded by his children and dozens of family and friends, Mr Combs has watched Ms Ventura from his chair at the defence table just a few dozen feet away.

All the while, US District Judge Arun Subramanian has pushed attorneys to stay on schedule, as prosecutors have expressed worry their star witness could go into labour with her third child as soon as this weekend.

On her first day on the stand, Ms Ventura began by taking prosecutors through the start of her tumultuous relationship with Mr Combs, whom she met when she was a 19-year-old aspiring musician. Mr Combs, 17 years her senior, signed her onto his record label.

Their romantic relationship began soon after, when Ms Ventura fell in love with the "larger-than-life" musician and entrepreneur, she said. But it was not long before she noticed a "different" side to him, Ms Ventura testified, at times wiping the tears from her eyes.

Mr Combs, she said, wanted to control every aspect of her life. He paid for her rent, her car, and her phone, sometimes taking the items away to "punish" her when he was upset, she said.

Eventually, the relationship turned violent. She testified about the time when he attacked her because she was sleeping, slashing her eyebrow as he threw her onto the corner of her bed as her two friends tried to stop him. The court was shown a photo of the gash that Ms Ventura said Mr Combs hired a plastic surgeon to fix secretly. There was another time at a party where he kicked her head as she cowered behind a toilet in a bathroom stall, she said.

While jurors remained concentrated on her testimony and the evidence, betraying little emotion, some in the courtroom wiped away tears or looked away from the graphic photos and videos - including the viral video of Mr Combs beating and dragging Ms Ventura in the hallway of the InterContinental Hotel in Los Angeles in 2016.

Published by CNN last year, the video has been viewed by millions - including many of the jurors before they were seated in the trial - and Ms Ventura, who was forced to rewatch the incident of abuse several times this week.

Ms Ventura testified that the hotel incident took place after she tried to leave a "freak-off", a sexual encounter in which the couple would hire male escorts to have sex with Ms Ventura while Mr Combs watched and recorded from the corner.

Ms Ventura said the rapper introduced her to freak-offs around a year into their relationship, and at first, she did it to make him happy.

But over time, the encounters humiliated her, she said. They would sometimes last as long as four days, and require Ms Ventura to take countless drugs to stay awake, she said. She endured injuries like painful urinary tract infections - and once even blacked out, waking up in the shower, she said.

"It made me feel worthless," she told the court. "Freak-offs became a job where there was no space to do anything else but to recover and just try to feel normal again."

The couple would go on to have "hundreds" of freak-offs, Ms Ventura estimated.

After years of temporary break-ups - some fuelled by Mr Combs' affairs - Ms Ventura ended her relationship with Mr Combs for good in 2018, the same year she alleges the rapper raped her in her home as she cried.

Ms Ventura went on to date and marry her personal trainer, Alex Fine, with whom she has two children, but the trauma of her relationship has stayed with her.

Through tears, Ms Ventura told the court of a time two years ago when she considered taking her own life, when traumatic flashbacks of her time with Mr Combs became too much to handle. Her husband helped her seek therapy to recover, she said.