A federal judge heard arguments Wednesday in a case that could put Uber s self-driving car development on hiatus, based on claims from rival Waymo that Uber stole some of its trade secrets .

Waymo, a Google -spinoff, is seeking an injunction against Uber s program, effectively halting it for the duration of the trial. Self-driving vehicles are central to Ubers long-term business strategy, so halting work on them could have severe financial repercussions for the company.

At the heart of the case is a technology called LiDAR that helps an autonomous vehicle map out and navigate its surroundings as its driving.

Waymo lawyers presented evidence that a former executive named Anthony Levandowski downloaded Waymos LiDAR designs, along with some 14,000 other documents, before he left the company in January 2016. Soon after Levandowski left, he started a competitor company named Otto that was purchased by Uber for $680 million less than a year later.

Waymo lawyer Charles Verhoeven portrayed Otto as little more than a shell company, founded by Levandowski for no other purpose than selling valuable, confidential technology to Uber.

And while U.S. District Court Judge William Alsup conceded, speaking of Waymos evidence, that hes never seen a record this strong in 42 years, ultimately the company struggled to prove that Uber asked Levandowski to steal Waymos files on Ubers behalf.

That matters, since Waymo is suing Uber not Levandowski.

Im listening very carefully to see the proof that shows that Uber was aware that he downloaded information, Alsup told Charles Verhoeven. That would be pretty damning if you had that.

Verhoeven maintained that proof does exist, but its among 3,500 or so documents, which Uber says contain confidential information that it refused to release. Complicating matters, Levandowski has asserted his fifth amendment rights and refused to testify. (He also stepped away from Ubers LiDAR-related research for the duration of the case).

In lieu of the smoking gun Alsup sought, Verhoeven presented evidence claiming Levandowski conspired with Uber before he left Waymo.

There was this clandestine plan all along that Uber and Levandowski had a deal, he said.

That evidence includes emails Levandowski exchanged with Uber while he still worked at Waymo, and 5.3 million shares of stock (worth approximately $250 million) Uber granted Levandowski on Jan. 28, 2016, the day after he left Google. Uber responded by clarifying it actually awarded Levandowski the stock months later during the Otto acquisition, but set the vesting date earlier as a courtesy.

Uber, represented by outside lawyer Arturo Gonzalez, denied any wrongdoing, as it always has.

We are adamant that we did not use any of their secrets, he said.

Notably, however, Uber also hasnt gone out of its way to defend Levandowski.

Gonzalez said Uber didnt have any basis to dispute that Levandowski downloaded the 14,000 files. While its conceivable he brought them into work on a personal laptop and consulted them, Gonzalez said, Theres no evidence that it happened.

Ubers ultimate goal is to move the case out of the public spotlight and into arbitration , where this could all be settled privately.

The judge is expected to make a decision on the injunction sometime in the next couple weeks. A trial should it come to that would likely begin sometime in October.