In a closely watched antitrust trial, a behavioral economist and professor at the California Institute of Technology, Antonio Rangel, testified that Google fought hard to become the default search engine on smartphones and browsers in order to manipulate users' choices. Rangel explained that by controlling users' fixations and manipulating their choices through default settings, Google can keep users hooked on its search engine and other lucrative services. He emphasized the powerful impact of default settings on consumer decisions, stating that users generally stick with the default option set on their computers and smartphones. Rangel cited a 2015 email from a Google employee, which warned that losing default status on Apple's Safari browser would be a "code red" for the company, highlighting the vulnerability of Google's position if defaults were to change.

However, Google attorneys fired back during cross-examination, arguing that consumers choose Google's search engine due to its quality, not its default status. They disputed Rangel's claims and reiterated their central argument that users can easily switch their default search engine if they desire. Rangel, in response, presented evidence that switching default search engines is not as easy as Google portrays, citing his own experience with an Android smartphone, which took 10 steps to switch from Google to Microsoft's Bing.

Former Google executive Chris Barton also testified, revealing that Google recognized the immense value of default search status on mobile devices early on. Barton, who worked on partnerships with major mobile carriers from 2004 to 2011, explained that Google aggressively pursued exclusive agreements to become the default search engine for various carriers and Android smartphone makers. This testimony supports the Department of Justice's claim that Google has engaged in anti-competitive measures to maintain its dominant position in the US search market.

The antitrust case against Google is the largest of its kind in over two decades, and the outcome will be determined by US District Judge Amit Mehta rather than a jury. If the Justice Department succeeds, Mehta could order Google to discontinue certain business practices or even break up the company. The case has far-reaching implications for other Big Tech firms, including Amazon and Apple, which have also faced scrutiny from federal regulators over their business practices.