A U.S. judge ruled Monday that Google's search engine has been illegally exploiting its dominance to suppress competition, in a blow to the famous global search engine.

The highly anticipated decision issued by U.S. District Judge Amit Mehta comes nearly a year after the start of a trial pitting the U.

S. Justice Department against Google in the country's biggest antitrust showdown in a quarter century. After reviewing reams of evidence that included testimony from top executives at Google, Microsoft and Apple during last year's 10-week trial, Mehta issued his potentially market-shifting decision three months after the two sides presented their closing arguments in early May.

"After having carefully considered and weighed the witness testimony and evidence, the court reaches the following conclusion: Google is a monopolist, and it has acted as one to maintain its monopoly," Mehta wrote in his 277-page ruling. He said Google’s dominance in the search market is evidence of its monopoly. Google "enjoys an 89.

2% share of the market for general search services, which increases to 94.9% on mobile devices,” the ruling said. It represents a major setback for Google and its parent, Alphabet Inc.

, which had steadfastly argued that its popularity stemmed from consumers' overwhelming desire to use a search engine so good at what it does that it has become synonymous with looking things up online. Google's search engine currently processes an estimated 8.5 billion queries per day world.