[Read our latest story on Vicente Zambada Niebla’s testimony in the El Chapo trial.]

Aside from the chiefs who ran the organization, probably no one knows more about the Sinaloa drug cartel than Vicente Zambada Niebla.

A son of Ismael Zambada García, one of the cartel’s leaders, Mr. Zambada, from an early age, was groomed to take control of the group.

But on Thursday, in a spectacular reversal, the cartel prince betrayed his father — and his birthright — testifying for more than five hours about nearly every aspect of the drug-trafficking empire: smuggling routes, money-laundering schemes, bloody wars, personal vendettas and multimillion dollars in bribes. When it came to the enterprise he seemed poised to lead one day, Mr. Zambada proved he knew almost everyone and everything.

His bravura turn on the witness stand came at the midway point in the drug trial of his father’s former partner, Joaquín Guzmán Loera, the infamous crime lord known as El Chapo. Since the trial began in November, seven other witnesses who worked with Mr. Guzmán have testified against him. But none were more conversant with the structure and details of the kingpin’s business than Mr. Zambada.