The court battle between the US justice department and Google has entered its second day, as the United States government seeks to prove that the tech behemoth illegally leveraged its power to maintain a monopoly over internet search engines. The trial is a major test of antitrust law and could have far-reaching implications for the tech industry and for how people engage with the internet. The question at the heart of the trial is whether Google’s place as the search engine for most Americans is the result of anti-competitive practices that gave internet users no other choice but to use its services. On the first day of the trial, attorneys for the justice department and the dozens of states that have joined in the suit accused Google of shutting out competition through billion-dollar agreements with companies such as Apple and Samsung. The justice department lawyer Kenneth Dintzer alleged Google spends $10bn a year in deals to ensure it is the default search engine on devices such as the iPhone, effectively blocking meaningful competition and positioning Google as the gatekeeper of the internet. “They knew these agreements crossed antitrust lines,” Dintzer said. Google’s opening statement gave a window into how the company and its lead attorney, John Schmidtlein, plan to defend against the accusations. Schmidtlein argued that Google has achieved its dominance over online search – the government estimates it holds about a 90% market share – because it is simply a better product than alternatives such as Microsoft’s Bing search engine. Consumers are free to switch default settings with “a few easy clicks” and use other search engines if they please, Schmidtlein told the court on Tuesday. The justice department called its first witness, Google’s chief economist Hal Varian. Over the course of two hours, Dintzer presented Varian with internal memos and documents dating back to the 2000s that showed him discussing how search defaults could be strategically important. One internal communication from Varian warned over antitrust issues that “we should be careful about what we say in both public and private”. On Wednesday, the justice department called the former Google executive Chris Barton, who had worked in partnerships and was an employee from 2004 to 2011. The department questioned Barton about the value of those partnerships in establishing dominance over the market. “As we recognized the opportunity for search on mobile phones, we began to build a product team,” Barton said, according to Reuters. As with the first day of the trial, the government has tried to show that Google saw the importance early on of making deals and securing its position as the default search engine on devices. The documents and witnesses it has brought up have so far been from over a decade ago, when the government says Google was first beginning to forge agreements that helped it monopolize search. The justice department has also alleged that Google was aware of possible antitrust violations and has consciously tried to obscure its actions. The government presented a document in court from an internal Google presentation on antitrust, which warned employees to avoid mentioning “market share” or “dominance”. The trial is set to last 10 weeks and feature numerous witnesses, as well as internal Google documents that the justice department hopes will show that monopolizing search has long been a top priority at the company. Judge Amit Mehta will decide the case, and there is no jury in the trial.