(Bloomberg) -- A senior Google executive sought to refute the US Justice Department’s antitrust case over its display advertising technology business, testifying that it faces “fierce competition” from the likes of Microsoft Corp., Amazon.com Inc. and Meta Platforms Inc.

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But the federal judge overseeing the trial in Virginia called the testimony “highly questionable” and potentially “tainted” given that Google officials had known about antitrust concerns over the ad tools since the US opened its probe in 2019.

The Justice Department, which accused the Alphabet Inc. unit of monopolizing online ad technology tools, rested its case Friday after two weeks of testimony. That allowed Google to start presenting its defense, calling as the company’s first witness Scott Sheffer, vice president of partnerships.

Sheffer, an 18-year veteran of Google, walked through the company’s various products and pointed out dozens of online rivals that provide “fierce competition” in the business.

US District Judge Leonie Brinkema, who will decide whether Google violated the law, chastised the company’s lawyers for presenting testimony she viewed as irrelevant.

“This doesn’t get to the core issues in this case,” she said, questioning Sheffer’s views on ad tech competition because the company has been aware of antitrust probes for more than four years. A group of state attorneys general filed an antitrust suit over the alleged monopolization in 2020 and the Justice Department filed its own case last year.

Sheffer said that Google has recently lost some clients to Microsoft Corp., which purchased AT&T Inc.’s ad tech business in 2022. Also that year, Netflix Inc. moved from Google to Microsoft’s advertising tools, in part, he said, because the Windows maker offered a financial guarantee that was “quite large.”

Sheffer also detailed Google’s recent partnerships with X, the social media platform formerly known as Twitter, and Roku Inc., but Brinkema ruled that the company couldn’t offer the evidence because it had failed to disclose the information to the government earlier in the case.

Google is expected to continue its defense next week, after which the Justice Department will have an opportunity to recall witnesses before the trial concludes.