Robert Menendez

At the corruption trial of Robert Menendez, the former powerful senator from New Jersey, the jury may have seen no more telling a collection of evidence than the actual bribes he received — bars of gold bullion that glinted under the courtroom lights.

But the trial also turned on the testimony of an obscure insurance broker who was charged in the case and then, before trial, switched sides.

The broker, Jose Uribe, pleaded guilty and cooperated with the authorities, meeting 36 times with the government and providing what one prosecutor told the jury was “devastating evidence of Menendez’s culpability.”

Now, Mr. Uribe will become the final defendant in the sprawling case to face justice when he appears on Thursday in Federal District Court in Manhattan for sentencing.

Mr. Uribe testified as a key government witness at two trials — that of Mr. Menendez and two businessmen charged with him, and that of Nadine Menendez, the former senator’s wife, who shuttled messages and bribes to her husband. The couple and the businessmen were all convicted and given stiff prison sentences.

Mr. Uribe testified at one point that he gave Ms. Menendez a Mercedes-Benz in exchange for securing “the power and influence” of the senator. In another piece of memorable testimony, Mr. Uribe told jurors about witnessing Mr. Menendez ring a hand-held bell to summon Ms. Menendez from inside the couple’s home.

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