WASHINGTON, May 2 (Reuters) - U.S. District Judge Amit

Mehta peppered the Justice Department and Alphabet's

Google with questions in the first day of closing arguments in

the government's antitrust lawsuit against the online search

leader.

The Justice Department hammered away at Google in a trial

that started on Sept. 12, arguing the search engine giant is a

monopolist and illegally abused its power to favor its bottom

line.

The judge noted that during the trial, Microsoft ( MSFT )

acknowledged it did not invest enough in mobile search. "That's

not anticompetitive, the fact that Google was smart enough to

get on the mobile bandwagon before Microsoft ( MSFT )," Mehta said.

The government agreed, but responded that a "mistake by one

rival doesn't mean Google gets to monopolize this market

forever."

Google lawyer John Schmidtlein rejected contentions the

company had engaged in anticompetitive conduct.

This case, filed by the Trump administration, was the first

of five aimed at reining in the market power of tech leaders.

The second, against Facebook parent Meta, was also filed

during the Trump administration, while Biden's antitrust

enforcers have followed with a second case against Google and

cases against Amazon.com ( AMZN ) and Apple Inc. ( AAPL )

In this non-jury trial, Mehta will weigh whether Google

violated the law, and will later look at any punishment if

needed.

Witnesses from Verizon, Android maker Samsung

Electronics ( SSNLF ) and Google itself testified about the

company's annual payments - $26.3 billion in 2021 - to ensure

that its search is the default on smartphones and browsers, and

to keep its dominant market share.

In his testimony, Google CEO Sundar Pichai acknowledged the

importance of making its search engine the default on phones,

tablets and laptops to keep users loyal, saying: "We definitely

see value."

In turn, Google has argued the government was wrong to

allege it broke the law to hold onto its massive market share,

saying its search engine was wildly popular because of its

quality and that dissatisfied users can easily switch.

Despite Google's multibillion-dollar payments and Pichai's

statement, Google's lawyers have argued that being the default

has limited value and that users will not stick around if they

are unhappy.