Judge Grills U.S. and Google on Antitrust Claims

The judge overseeing a landmark U.S. antitrust challenge to Google tried to poke holes in both sides’ cases during closing arguments Thursday, as he weighs a ruling that could reshape the technology industry.

Judge Amit P. Mehta was presiding over the first day of closing arguments in the most consequential tech antitrust case since the U.S. government sued Microsoft in the late 1990s. The Justice Department has sued Google, accusing it of illegally shoring up a monopoly in online search. Google has denied the claims.

On Thursday, Judge Mehta questioned...