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Lawyers for Joaquín Guzmán Loera, the infamous drug lord known as El Chapo, claimed on Tuesday that for decades their client had been framed by a vast conspiracy of plotters, including his chief lieutenant in the Sinaloa cartel, American drug agents, and the last two presidents of Mexico.

The defense’s claim was an unexpected start to Mr. Guzmán’s drug conspiracy trial, which after several delays on Tuesday began under tight security in Federal District Court in Brooklyn.

During an impassioned opening statement, one of Mr. Guzmán’s lawyers, Jeffrey Lichtman, said that the real mastermind of the cartel, which Mr. Guzmán has been accused of running for decades, was his longtime partner Ismael Zambada Garcia.

Describing Mr. Guzmán as no more than “a scapegoat,” Mr. Lichtman argued that Mr. Zambada, known as El Mayo, had been the one to oversee 20 years of drug shipments into the United States, and who repeatedly paid off — to the tune of millions of dollars — a “completely corrupt” Mexican government, including top officials like President Enrique Peña Nieto and his predecessor, Felipe Calderón.