NEW YORK -- Jurors at the trial of Mexican drug lord Joaquin "El Chapo" Guzman ended their third day of deliberations at his U.S. trial Wednesday without a verdict after asking whether killing someone over personal beef could be part of a drug-trafficking conspiracy.

In the same note to the judge, the jury also requested to review lengthy transcripts of testimony of three co-operating narcos who testified against Guzman. It was to resume deliberations on Thursday.

At trial, jurors heard testimony from 14 co-operators, including many who described Guzman's willingness to use violence against enemies of a cartel that prosecutor say smuggled at least 200 tons of cocaine into the U.S. over two decades. The defence has accused the co-operators of making him a scapegoat for their own crimes.

In response to the question in the jurors' note, the judge told them that if they found that a killing was "wholly personal" and "unrelated to drug trafficking," it would not constitute a drug-trafficking crime.

It was unclear whether the jury was focusing on a particular murder of many in the case. But the trascripts they requested contain testimony alleging Guzman once ordering the killing of a member of an allied cartel in 2004 because the victim disrespected him by not shaking his hand at the close of a meeting.

The victim "just left him standing there with his hand extended," one of the witnesses, Jesus "El Rey" Zambada, testified.

Word spread that Guzman was "very upset" by the snub and ordered a hit, Zambada said. The victim was killed later that year - payback that ended up fueling a war between the Sinaloa and Juarez cartels.

The 61-year-old Guzman attained near-mythical status by escaping jail twice in Mexico. He was recaptured and sent in 2017 to the United States, where he has been held in solitary confinement ever since.

He could get life in prison if convicted of multiple drug-trafficking conspiracy counts.