Jurors in the trial of Mexican drug lord Joaquin "El Chapo" Guzman have heard recordings of his phone calls which prosecutors say the FBI intercepted and deciphered after turning his tech expert.

An undercover agent met Cristian Rodriguez in 2010 while posing as a gangster who wanted to buy his own encryption system, and over time the FBI managed to persuade him to "cooperate" with investigators while still working for the drug kingpin.

The Sinaloa cartel's computer servers were moved to the Netherlands, where agents could more easily unscramble the data to eavesdrop on Guzman as he ran his empire, the jury heard.

Investigators were able to identify Guzman's voice through recordings of conversations he had while locked up in Manhattan's Metropolitan Correctional Centre as well as an interview he did with actor Sean Penn for Rolling Stone magazine, the New York Post reported.

Who is drug lord 'El Chapo'?

Agent Stephen Marston, who helped run the operation, said the agency had caught Guzman on tape between 100 and 200 times and wiretapped around 800 calls after infiltrating his encrypted messaging system.


He described Guzman's voice to the court in Brooklyn, New York, on Tuesday, as "sing-songy" and "high-pitched".

In one call, Guzman can be heard ordering the cartel's security chief Orso Ivan Gastelum, known as "El Cholo", to "take it easy with the police" after he boasted he had "kicked their asses".

"Talk to them, you know they are policemen. It's better not to smack them around," Guzman says.

Gastelum responds: "Well, you taught us to be a wolf, acting like a wolf, I'm remembering. And that is how I like to do it."

Image: Guzman's trial is expected to last for months

In another call, Guzman can be heard discussing bribing a police officer with an associate called Gato, the New York Times reported.

"Is he receiving the monthly payment?" Guzman asks.

"Yes," says Gato, "he's receiving the monthly payment" - before handing the phone to the police officer himself.

Guzman, 61, was extradited to the US in 2017 after escaping from a Mexican prison twice, but his lawyers insist he is being framed.

The alleged Sinaloa co-founder is accused of smuggling more than 155 tonnes of cocaine into the US over 25 years.

He faces 11 trafficking, firearms and money laundering charges and is likely to be jailed for life if convicted.