NEW YORK (Reuters) - Prosecutors in the trial of “El Chapo” Joaquin Guzman on Tuesday played excerpts from what they said were incriminating phone calls made by the accused Mexican drug lord and intercepted by the FBI after they infiltrated his encrypted messaging system.

FILE PHOTO: Mexico's top drug lord Joaquin "El Chapo" Guzman is escorted as he arrives at Long Island MacArthur airport in New York, U.S., January 19, 2017, after his extradition from Mexico. U.S. officials/Handout via REUTERS/File Photo

Nearly two months into the trial of Guzman on charges of drug trafficking as leader of the Sinaloa cartel, FBI special agent Steven Marston testified the 61-year-old was easily identifiable by his higher-pitched voice, which had “kind of a sing-songy nature to it” and a “nasally undertone.”

The phone call excerpts that wafted through the Brooklyn courtroom on Tuesday included discussions of dealings with local officials, including one where Guzman appears to admonish an associate to be careful dealing with police.

“Well, you taught us to be a wolf, acting like a wolf,” the associate replied.

Guzman was extradited to the United States in January 2017 to face charges of trafficking cocaine, heroin and other drugs into the country. Prosecutors have said he also played a central role in a Mexican drug war in which more than 100,000 people have died.

Guzman’s lawyers have portrayed their client as a scapegoat for what they called Sinaloa’s real leader, Ismael “El Mayo” Zambada, who also faces U.S. charges but remains at large.

The trial began Nov. 13 and is expected to last a few more weeks. Guzman faces life in prison if convicted.

Marston said the FBI tapped into more than 800 calls on the encrypted system with the help of a cooperating witness, Cristian Rodriguez.

The agent said the system’s servers were moved to the Netherlands, where they “would not be suspicious” to Sinaloa, and that calls were intercepted from April 2011 to January 2012.

Jurors had previously heard from former Guzman associates testifying about multi-ton drug shipments, deadly wars between rival drug lords, and corruption by Mexican public officials.

The defendant mostly sat quietly during testimony, but waved enthusiastically to his wife in the courtroom before it started.

Tuesday’s proceedings began with testimony from government witness Edgar Galvan, a low-level drug trafficker who the defense said fabricated payments from another trafficker to Guzman with the hope of reducing his own 24-1/3-year prison term.

Galvan denied making up the payments, though he admitted to having previously lied to investigators.

“Would you say you’re a pretty good liar?” defense lawyer William Purpura asked Galvan.

“I used to be,” Galvan said.

(The story corrects spelling of cooperator’s first name provided by the Justice Department to Cristian, not Christian, Rodriguez in eighth paragraph.)