ZeniMax Media, parent company of Doom creator id Software, will prove that Facebook-owned Oculus VR deliberately destroyed evidence in an attempt to cover up theft of some of the foundational elements of its virtual reality headset and the tech behind it, ZeniMax said in a statement released to Polygon today.

The comment comes as the $2 billion 2014 lawsuit over who actually created the tech behind the Oculus Rift headset goes to trial in a Dallas courtroom.

While reiterating the statement it provided to Polygon last week, Oculus did confirm to Polygon that Facebook co-founder Mark Zuckerberg is scheduled to testify Tuesday.

Others expected to testify in the weekslong trial are former id Software chief tech officer and co-founder John Carmack, and a bevy of tech and forensic experts.

ZeniMax sued Oculus in May 2014

Rockville, Maryland-based ZeniMax sued Oculus in May 2014, alleging that the VR startup misappropriated trade secrets in the development of the Oculus Rift headset. The lawsuit was filed weeks after ZeniMax publicly accused Carmack of providing technology to Oculus. Oculus has said it will disprove those claims.

According to ZeniMax’s complaint, Oculus co-founder and Rift inventor Palmer Luckey — along with a half a dozen ex-ZeniMax employees who are now working at Oculus — are building the Rift based on years and millions of dollars’ worth of ZeniMax’s research and copyrighted code.

Oculus, which is now owned by Facebook, denies the allegations, saying the lawsuit came to a head after Facebook purchased the company and as a “chance for a quick payout.”

The opening arguments came last week. ZeniMax declined to comment at the time, but a spokesperson provided a statement today.

“ZeniMax and id Software are the visionary developers of breakthrough VR technology”

“With the start of the trial of our case in Federal District Court in Dallas against Defendants Facebook, Oculus and its management, ZeniMax and id Software welcome the opportunity to present substantial evidence of the Defendants’ misappropriation of our Virtual Reality (VR) intellectual property,” ZeniMax said in a statement provided to Polygon. “That evidence includes the theft of trade secrets and highly confidential information, including computer code. ZeniMax will also present evidence of the Defendants’ intentional destruction of evidence to cover up their wrongdoing. ZeniMax and id Software are the visionary developers of breakthrough VR technology, and look forward to the vindication of our claims.”

The accusation of destruction of evidence may be based on an interpretation of findings of a court-appointed forensic expert who was ordered to examine Carmack’s computer. The details of those findings, while potentially important to the case, remain mostly under seal, likely until they’re presented in court.

Last week, an Oculus spokesperson provided the company’s statement about the trial. We reached out to the company today for further comment and will update this story if they respond.

“We’re eager to present our case in court,” Oculus said in an emailed statement. “Oculus and its founders have invested a wealth of time and money in VR because we believe it can fundamentally transform the way people interact and communicate. We’re disappointed that another company is using wasteful litigation to attempt to take credit for technology that it did not have the vision, expertise, or patience to build.”

“We’re eager to present our case in court”

In October, a judge ordered that Samsung had three weeks to provide details to ZeniMax about the work the company did with Oculus in co-creating the Samsung Gear VR, which runs on Oculus software.

Last August, ZeniMax amended its complaint to be more blunt about the accusations against Oculus, saying the company misappropriated trade secrets, benefiting from years of the company’s research and experimentation with virtual reality technology.

“For many years, ZeniMax invested tens of millions of dollars in research and development, including research into virtual reality and immersive technologies. In 2011 and 2012, John Carmack, a singularly experienced and highly proficient ZeniMax programmer who was at that time Technical Director for ZeniMax’s Texas-based subsidiary, id Software, conducted research to address technological issues associated with virtual reality,” the complaint reads. “Carmack and other ZeniMax employees conducted that research at ZeniMax offices, on ZeniMax computers, and using ZeniMax resources.”

The history of Luckey, the Oculus Rift, Carmack and ZeniMax-owned id Software, is a complicated and entwined one. You can read more about it in our previous coverage of the ongoing suit.

Update: Story updated with confirmation of Zuckerberg’s potential testimony.