A Brooklyn courtroom Thursday heard notorious Mexican kingpin Joaquin “El Chapo” Guzman in action, listening in on a recorded phone call where he can be heard coordinating a cocaine deal with a member of a Colombian guerrilla group.

“Tomorrow I will send a technician over there to see [the cocaine],” Chapo insists on the call, which was secretly taped in May 2010.

The drug lord repeatedly insists the cocaine must be inspected before he sends a $50,000 advance for the six ton deal, said government witness Jorge Milton Cifuentes, who trafficked cocaine for Chapo. The 52-year-old Colombian explained the Sinaloa cartel had received inferior drugs from the guerrillas before.

Jurors listened intently to the damning exchange, in which an unidentified member of the Revolutionary Armed Forces of Colombia–People’s Army, or FARC, tries to sell the cocaine to Chapo for $2,100 per kilo of cocaine. The deal fell through, the drug trafficker testified.

While it wasn’t clear who had recorded the call, Cifuentes testified earlier that Chapo had been having trouble with his “cryptography” system — which was meant to block eavesdropping — because the cartel IT guy forgot to file some paperwork.

Later Thursday, Cifuentes admitted under cross-examination he’d been a lifelong liar who did everything he could to game the system.

He started in the drug business at age four, and first went to prison at age 18. He told the court prison “wasn’t that horrible.”

“Was it helped by the fact that you were having sex with the wife of one of your guards?” Chapo’s defense attorney Jeffrey Lichtman asked, prompting objections from prosecutors.

Jurors sat riveted as Lichtman forced Cifuentes to admit a series of tidbits he’d neglected to disclose to the government — and to concede he was so greedy he continued to work with Chapo’s partner, Ismael “El Mayo” Zamaba, even though Zamaba had brutally murdered his best friend, Umberto Ojeda.

Mayo’s hitmen fired more than 40 bullets into Ojeda’s armored car in 1997 as his young daughter sat inside, Cifuentes confirmed. Ojeda was shot in the heart, and the child remained locked inside the car with her dead father for an unknown period of time before she was rescued.

Cifuentes also claimed he once aborted an attempt to kill a fellow inmate with a cyanide-seasoned arepa by tossing it out the prison window.

“Because you don’t like to hurt people?” Lichtman sarcastically asked the drug trafficker, who previously said he’d ordered the successful murders of at least three people.

“Not people who aren’t in my line of attack,” responded Cifuentes, who grew so uncomfortable under cross that he took to guzzling the bottles of water provided by the court.

He also confessed to having a series of phony IDs made up — and even went so far as to have fake diplomas printed to impress his fellow drug dealers, despite not having graduated high school.

After Cifuentes stepped down Thursday, Judge Brian Cogan announced he would not be admonishing members of the defense team for their tweets and interviews, as prosecutors previously requested.

“As I’m sure the government has noticed, I’ve limited my tweeting to Donald Trump and Barcelona soccer,” defense attorney Eduardo Balarezo quipped following Cogan’s ruling.

Chapo faces life behind bars if convicted of various drug trafficking and conspiracy charges.