(CNN)Courtroom sketch artists at the trial of alleged drug kingpin Joaquin "El Chapo" Guzman were barred from drawing the facial features or distinguishing hairstyle of a key witness on Monday.
Security at the 'El Chapo' trial is so strict that sketch artists can't draw this witness's face
In addition, the artists were required to show the sketches to government prosecutors for approval before they could be distributed, the judge in the federal trial said.
And in a related move, prosecutors asked the judge to impose sanctions on defense counsel because Guzman's wife used a cell phone in the courthouse, according to a court filing.
The incidents show the intense security measures at play in the case and provide glimpses into the lengths to which the government is going to provide security for witnesses in Guzman's high-profile trial.
Guzman faces charges of international drug trafficking and conspiracy to murder rivals, and he has pleaded not guilty.
The security limitations were made clear as part of the testimony from Miguel Angel Martinez, a cooperating witness who worked for El Chapo in the Sinaloa cartel between 1986 and 1998. Martinez testified on Monday and Tuesday about his experience working with Guzman as they moved drugs into the US by airplane, tunnel, and truck.
The resulting sketch from artist Christine Cornell shows a witness on the stand with a blurred face and a bald head, as Guzman looks on.
Guzman's trial, which could last four months, began two weeks ago under unprecedented security measures, including armed escorts for the anonymous and partly sequestered jurors.
Heavily armed federal marshals and officers with bomb-sniffing dogs stood guard outside the courthouse. Those who wished to witness the trial in person had to pass through two separate security screenings -- an X-ray machine and metal detector -- to enter the courthouse, and a similar screening to enter the courtroom.
Martinez, known by his aliases "El Gordo," "El Compadre," or "El Tololoche," identified Guzman as his boss and said he never took orders from anyone else during his time with the cartel.
"Él era el jefe," he said, referring to Guzman -- "He was the boss."
Martinez said he was one of the closest people to Guzman during his time in the cartel. They were associates, friends, and "compadres," and Chapo baptized Martinez's son in 1989. He first met Chapo in late 1986 and last saw him in jail in Mexico in 1994.
Martinez said he was a pilot for the cartel and was responsible for receiving shipments of drugs from Colombia to Mexico for Chapo, and then those drugs would be sent to the US. He personally flew in planes with drugs coming from Colombia and directed the Colombian pilot to clandestine landing strips that Chapo had in Agua Prieta and Cumpa Sonora, locations near the Arizona border.