Casandra Ventura, the star witness of the federal sex-trafficking and racketeering trial of the music mogul Sean Combs, cried during her first day on the stand on Tuesday as she testified about drug-fueled sex sessions with male prostitutes that could last several days and made her feel “disgusting” and “humiliated.” He has pleaded not guilty.

Ms. Ventura, who is known as Cassie, had accused Mr. Combs of rape and years of physical abuse in a 2023 lawsuit that was quickly settled. Her testimony is vital to the prosecution’s case, and she will return to the stand on Wednesday.

Here are four takeaways from her initial testimony:

The drug-fueled freak-offs could last for days.

The sex sessions known as freak-offs ranged from roughly 36 hours to as long as four days, Ms. Ventura testified, sometimes without any sleep. She recalled drinking, taking drugs and having sex with strangers while staying up for “days on end.”

Drugs helped keep them awake, she said. But then she would need to recover from the drugs, dehydration and sleep deprivation.

“The freak-offs became a job where there was no space to do anything else but to recover and just try to feel normal again,” Ms. Ventura testified.

The freak-offs orchestrated by Mr. Combs “took a big chunk of my life,” she testified, saying that they continued for years — sometimes on a nearly weekly basis. At the end of the sessions, she said, the hotel room linens were often soiled baby oil residue as well as bodily fluids including blood and urine.