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SAN FRANCISCO — Former Uber CEO Travis Kalanick testified as a star witness on Tuesday in one of the most revealing Silicon Valley cases in ages, pitting Uber against Waymo, the self-driving car company owned by Google's parent company, over the alleged theft of trade secrets.

At issue is whether Anthony Levandowski, a former Google employee, downloaded files related to self-driving car technology and took them to Uber, thereby accelerating development of Uber's autonomous driving operations.

The lawsuit has highlighted the cutthroat competition in Silicon Valley over talent and technology related to self-driving cars. It's also unusual to see such a high-profile civil case play out publicly in court rather than being settled behind closed doors.

Jurors heard testimony that Kalanick and Levandowski participated in a brainstorm — termed a “jam sesh" — at which Kalanick wrote on a whiteboard: "Laser is the sauce!"

The "sauce" in this case is the technology that helps self-driving cars see the world around them. The lasers are a part of a radar technology called lidar, which Levandowski had been working on while at Google.

Kalanick acknowledged on the witness stand that Uber did not have that "sauce" until it acquired Otto, Levandowski's autonomous truck start-up, for $680 million in August 2016.

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“I wanted to hire Anthony Levandowski and he wanted to start a company,” Kalanick said. As a result, he wanted to “create a situation where [Levandowski] felt like he started a company, and I felt like I hired him."

Levandowski was not named in the case.

It was the first time the public had heard from Kalanick in person since he resigned as Uber CEO last June amid questions over his leadership abilities. At the time, the company was grappling with how to fix what was described by former employees as a culture of gender discrimination and sexual harassment.

Kalanick, testifying at federal court in San Francisco, kept his answers short, mostly "yes" or "no."

Waymo's attorney began by establishing just how crucial Kalanick believed autonomous vehicle development was to Uber's future, asking whether Kalanick believed Uber's survival counted on it.

"Yes," he answered.

The notoriously hot-headed Kalanick appeared to keep his cool when being questioned by Waymo's attorney, carefully answering each question between frequent sips of water.

Kalanick was called toward the end of the trial's second day, and he was expected to resume his testimony on Wednesday morning.

On Monday, the first day of the trial, Waymo CEO John Krafcik testified that he had continued to message with Levandowski even after he left Uber. "He had gone from someone I had considered a friend to someone I considered an enemy," he explained. "I needed to understand what he was doing."

There's a lot at stake. Waymo has estimated its damages at $1.9 billion. If Uber loses, it could end up having to fork over that cash while also curtailing its self-driving car efforts.