Son of "El Chapo," leader of Sinaloa cartel, appears in federal court

CHICAGO (CBS) – The son of infamous Sinaloa cartel drug lord Joaquin "El Chapo" Guzman was in federal court in Chicago where he pleaded not guilty to drug trafficking and other charges on Tuesday.

Both Joaquin Guzman Lopez and his father's old business partner, Ismael "El Mayo" Zambada, were arrested after exiting a plane in El Paso, Texas last Thursday.

Lopez was shackled in an orange jumpsuit in court on Tuesday and said he was innocent. He also explained, in fluent English, how he has thyroid and blood pressure issues.

Attorneys for the goateed son of "El Chapo" pushed back hard on allegations that he's flipped on the family business, the Sinaloa drug operation, an outfit that federal investigators said uses submarines, speed boats, and jumbo jets to flood the U.S. with thousands of pound of illegal drugs.

Zambada appeared in court in El Paso last Friday for an initial appearance. He entered a not guilty plea and waived his arraignment and detention hearings, according to court records.

Prosecutors said Lopez orchestrated a massive drug operation and money laundering outfit that helped fuel the U.S. fentanyl crisis. But it was still unclear how Lopez ended up in the hands of authorities.

Lopez's attorney declined to answer questions about how his client ended up on the plane which landed in El Paso last Thursday with the FBI waiting for him on the ground.

CBS News has reported that Zambada, who federal officials said co-founded the Sinaloa drug cartel and has evaded arrest for 50 years, was tricked by Lopez, who presented the flight as an opportunity to review real estate in Northern Mexico. Zambada's attorney said his client was "forced onto a plane, his legs tied to the seat by Joaquin, and brought to the U.S. against his will. The only people on the plane were the pilot, Joaquin and my client."

The U.S. Drug Enforcement Administration had a $15 million reward out for information leading to Zambada's arrest. Lopez's attorney adamantly pushed back on speculation that he flipped for a deal with law enforcement.

"To point out some really obvious lies, there absolutely is no cooperation agreement with the government, and there never has been for Joaquin Guzman Lopez," said Jeffrey Lichtman, Lopez's attorney.

CBS News Chicago pressed Lopez's attorney for clarity on how his client ended up in federal custody.

"It's very interesting. I don't disagree ... but, as I said, the allegations keep changing by the day," said Lichtman. "There's a few people that know what happened, I suppose, and eventually, it'll come out. It just may not come out today."

Lichtman also represented "El Chapo" and Lopez's brother, who is also in federal custody. The brothers will be back in court on the same day, in front of the same Chicago judge in September. Both will remain in custody until then.