Sheldon Silver, one of New York State's most influential lawmakers for two decades, abused his position to earn millions of dollars in illegal kickbacks, federal prosecutors told a jury on Tuesday.

"This is a case about a powerful politician who betrayed those he was supposed to serve in order to line his own pockets," Assistant U.S. Attorney Carrie Cohen said as Silver's criminal trial began in a Manhattan courthouse, just steps from the Lower East Side district that Silver has represented in the state Assembly since 1976.

But Silver's defense lawyer, Steven Molo, said prosecutors had "twisted" the normal negotiations and compromises that allow government to function into a crime.

RELATED: Facing corruption charges, New York Assembly Speaker Sheldon Silver says he 'will be vindicated'

"If the prosecutors don't like that system, they can do what democracies do: They can go to the people and seek change," he said. "Make no mistake: Mr. Silver did not sell his office."

The case is New York's highest-profile public corruption trial after years of scandals that have ensnared dozens of state lawmakers.

As speaker of the Assembly, Silver, a Democrat, was one of the so-called "three men in a room," along with the Senate majority leader and the governor, who essentially control all legislative business in Albany.

Dean Skelos, a Republican who served as Senate majority leader until his arrest earlier this year, is scheduled to go on trial for corruption in the same courthouse later this month.

Underscoring the stakes, Preet Bharara, the U.S. Attorney in Manhattan whose office is prosecuting Silver, 71, and Skelos, watched from the rear of the courtroom on Monday.

RELATED: Feds arrest Sheldon Silver, NY's Assembly Speaker, on corruption charges

Prosecutors say Silver earned $3 million in bogus fees for referring asbestos sufferers sent to him by a doctor to a personal injury law firm. The doctor secretly received $500,000 in taxpayer money at Silver's direction for his cancer research center, prosecutors say.

In addition, Silver is charged with collecting $700,000 in kickbacks for steering real estate developers to another law firm. The developers, prosecutors said, hired the firm in exchange for support from Silver on key legislation.

"Year after year, Sheldon Silver was on the take," Cohen said.

Molo largely did not deny the factual allegations, instead arguing that Silver's actions were legal.

Silver, he said, negotiated bills, did favors for friends and collected legitimate legal fees, all while pursuing laudable goals: promoting affordable housing, helping cancer patients and supporting medical research.

"How could that be twisted into a criminal charge?" Molo said.