Infamous Mexican drug lord Joaquin "El Chapo" Guzman didn't sound pleased on a 2011 phone call as he listened to his chief enforcer for his cartel try to justify a beat down he gave some crooked police officers. After the two went back and forth over how to respond to Mexican authorities who dared to interfere with cartel business, the exasperated kingpin finally gave orders to "just reprimand them, don't beat them up."

The animated exchange was heard publicly for the first time Tuesday at Guzman's drug-trafficking trial in federal court in Brooklyn, New York, in one of several recordings of phone calls intercepted by the FBI. Guzman didn't know at the time that the FBI had hacked into a custom encrypted communications system created for the Sinaloa cartel by Cristian Rodriguez, a computer tech based in Colombia.

FBI agent Stephen Marston testified that investigators flipped Rodriguez and had the cartel's computer servers moved to the Netherlands, where agents could more easily unscramble the data to eavesdrop on Guzman as he ran his empire from a mountaintop hideaway. An undercover agent met with Rodriguez under the guise of wanting to set up his own encrypted system, CBS News legal analyst Rikki Klieman reported on CBSN.

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"This IT guy, by the way, you have to remember, is really courageous," Klieman said. He "is simultaneously working for the cartel, knows how violent it is, and is working for the FBI."

The audio evidence followed weeks of testimony by former cartel members about the inner workings of Guzman's operation. Defense lawyers said the cooperators are the real culprits who are railroading their client to help their own cases.

The jury heard recordings of Guzman speaking in Spanish to his cohorts after the FBI agent testified that he had authenticated the defendant's voice — described by the agent as "sing-songy" and "high-pitched" — by comparing the recordings to others from other sources. He testified that, between April 2011 and January 2012, investigators captured scores of conversations that show Guzman to be a hands-on manager demanding details about a tunnel used to smuggle drugs, bribing law enforcement and other aspects of his wildly lucrative operation.

In a pair of phone calls, Guzman speaks to an unidentified woman who told him she could expand his American market beyond Los Angeles and into Ohio, according to English transcripts read to the jury by the agent. He inquires several times about the demand for methamphetamine, asking, "Do we have customers for 'ice'?"

The call with the notorious cartel security chief Orso Ivan Gastelum, known as "El Cholo," had him bragging that during a recent run-in with police officers, he "kicked their (behinds), the federals, all of them." Guzman responds that more diplomacy is needed.

"Don't be so harsh, Cholo," he said. "Take it easy with the police."

Gastelum agrees, but only reluctantly. "Well, you taught us to be a wolf, acting like a wolf, I'm remembering," he said. "And that is how I like to do it."