A disturbing 2016 video that shows Sean “Diddy” Combs assaulting singer Cassie, his former girlfriend, has emerged as a key battleground in his sex abuse case.

Last week, attorneys for the mogul suggested they could seek to have the tape excluded from his upcoming trial. Legal experts have described the video — taken in the hallway of an L.A. hotel in 2016 — as key evidence.

Combs faces charges of racketeering, sex trafficking and transportation for prostitution. He has pleaded not guilty and denies the charges.

So why is the tape such crucial evidence? Here is what we know.

What does the video show?

The video shows Combs chasing, kicking, dragging and hurling a glass vase at Cassie, a singer whose real name is Casandra Ventura. It corroborates parts of a civil lawsuit Ventura filed against Combs last year, which was settled a day after it was filed in U.S. District Court for the Southern District of New York.

The recording, dated March 5, 2016, shows Ventura in a hoodie and carrying a duffel bag, walking in a hotel hallway toward an elevator. Combs can be seen running down the same hallway, shirtless and holding a towel around his waist.

The lawsuit said it occurred at the InterContinental hotel in Century City. After Combs fell asleep, Ventura attempted to leave the room, the lawsuit said, but he awoke and “began screaming” at her. “He followed her into the hallway of the hotel while yelling at her,” the complaint said. “He grabbed at her, and then took glass vases in the hallway and threw them at her, causing glass to crash around them as she ran to the elevator to escape.”

Security footage captured from another angle shows him grabbing Ventura’s head and throwing her on the ground, where he kicks her multiple times. He can also be seen picking up her bags and trying to drag her back to the first hallway.

The footage also shows Ventura using a hotel phone by the elevators, as well as Combs going back to his hotel room and then separately seemingly shoving Ventura into a corner. He is also seen throwing a vase in her direction.

Ventura also accused Combs in her lawsuit of raping her, forcing her to engage in sex acts with male sex workers and introducing her to “a lifestyle of excessive alcohol and substance abuse” that required her “to procure illicit prescriptions to satisfy his own addictions.”

Why was it important?

It was obtained and broadcast by CNN earlier this year amid a sweeping federal probe of Combs.

Legal experts have described it as very strong evidence for prosecutors.

But after facing intense backlash after it was posted in May, Combs posted a video on Instagram in which he apologized for his behavior in the video.

Cassie’s legal team disputed the sincerity of his words.

What is the dispute over the tape now?

Combs lawyers this week accused the government of waging a campaign to leak evidence, including the tape. They said they might also ask a judge to exclude the tape from the trial.

Combs’ lawyers allege that the government, through investigators with the Department of Homeland Security, “engaged in a seven-month campaign … strategically leaking confidential grand jury material and information, including the 2016 Intercontinental videotape, in order to prejudice the public and potential jurors against Mr. Combs.”

They acknowledged in the court filing that prosecutors, after being informed of the attorneys’ intention to file the leak allegations, responded that the Department of Homeland Security “did not have possession of the videotape prior to CNN’s” making it public and that the CNN video “was not obtained through grand jury process.” Federal officials have yet to comment on the filing.

They also want the “suppression of any evidence leaked by government employees.”

Prosecutors have denied any government role in the leak. “The Government was not in possession of the video before its publication by CNN. Indeed, at the time of CNN’s publication, the Government did not possess any video of the March 2016 incident,” prosecutors wrote.

What’s next?

A judge has yet to weigh in on the accusations but both sides have agreed not to speak about case specifics to the media.

Combs remained behind bars as his lawyers made a third bid for him to be released on $50 million pending a trial.

U.S. District Court Judge Arun Subramanian approved a May 5 trial date for Combs over April after his attorneys said they have piles of case documents and information to review.

Subramanian then asked the prosecution how long the trial would last.

Asst. U.S. Atty. Emily Johnson initially said three weeks, but then cautioned that there could be a superseding indictment on the horizon. Superseding indictments can include additional charges, more defendants, or both.

Marc Agnifilio, Combs’ lead attorney, said he believed the defense would take a week to make their case in a trial.