By Joseph Ax

NEW YORK (Reuters) - One of New York's most powerful politicians abused his office for a decade, orchestrating multimillion-dollar bribery schemes he kept hidden from public view through lies and deception, a U.S. prosecutor told jurors on Monday at the close of his corruption trial.

Sheldon Silver, who as speaker of the state Assembly wielded enormous political influence, collected $4 million in illegal kickbacks in exchange for official acts, Assistant U.S. Attorney Andrew Goldstein said in New York federal court.

"The full picture of his corruption was exposed in this courthouse," Goldstein said.

But Steven Molo, Silver's lawyer, said overreaching prosecutors had criminalized politics as usual.

"This is a theory without evidence," he said.

Silver's counterpart in the state Senate, former majority leader Dean Skelos, is himself on trial for corruption in the same Manhattan court.

The two trials represent the highest-profile cases in a string of recent prosecutions and scandals involving dozens of state lawmakers.

Silver, 71, and Skelos, 67, stepped down from their leadership posts after their arrests but continue to work as legislators, representing lower Manhattan and Long Island, respectively.

Under the state's system, the two legislative leaders and the governor comprise the so-called "three men in a room" who exercise virtually unfettered control over the legislative process in Albany.

With Preet Bharara, the U.S. Attorney in Manhattan, looking on from the audience, Goldstein said Silver awarded $500,000 in secret state grants to a cancer researcher, Robert Taub, who in turn referred asbestos patients to Silver's law firm. Silver received millions of dollars in fees from the firm as a result, Goldstein said.

"I will keep giving cases to Shelley because I may need him in the future - he is the most powerful man in New York State," Taub, who testified under a non-prosecution deal with the government, wrote in one 2010 email.

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But Molo said the men helped each other out of friendship, pointing to Taub's testimony that he did not steer patients to Silver as part of an explicit agreement for grant money.

"What kind of extortion scheme is it if the person being extorted doesn’t think he’s being extorted?" Molo said.

Silver is also charged with accepting $700,000 in kickbacks for steering real estate developers to another law firm, then watering down rent control legislation to help those developers.

Molo argued that Silver had to reach a compromise to pass the legislation, which nevertheless helped tenants more than developers.

Jury deliberations are expected to begin on Tuesday.

(Reporting by Joseph Ax; editing by Tom Brown, Richard Chang and David Gregorio)