A former bodyguard for the accused Mexican drug lord Joaquín “El Chapo” Guzmán has told a court that he watched his boss personally carry out three murders, including one in which the victim was buried alive.

The killings described by Isaías Valdez Ríos in federal court in Brooklyn, New York, were the first in the three-month-old trial to be attributed to Guzmán himself, rather than underlings following his orders.

Guzmán, 61, was extradited to the United States in 2017 and has been on trial since November on charges of trafficking vast amounts of cocaine, heroin and other drugs into the country as leader of the notorious Sinaloa cartel. His lawyers have claimed he was framed by another powerful drug trafficker, Ismael “El Mayo” Zambada.

Valdez, a 39-year-old former member of the Mexican army’s special forces, said he began working for Guzmán as a guard in one of his mountain hideouts around 2004. He was arrested in 2014 on US charges and is cooperating with prosecutors.

Valdez said that, around 2006 or 2007, Zambada delivered a member of the rival Arellano Felix drug cartel to Guzmán. Valdez said Guzmán was displeased to find that the prisoner had already been tortured with a hot iron.

Valdez said Guzmán kept the prisoner with him for several days, interrogating him twice. Eventually, he ordered his workers to dig a grave for the man, according to Valdez.

Guzmán then shot the prisoner with a handgun and ordered him buried, though he was still “gasping for air”, Valdez said.

On another occasion around the same time, Valdez said, an associate delivered two members of the Zetas, another rival cartel, to Guzmán.

After torturing the prisoners for about three hours, Valdez said, Guzmán ordered his underlings to dig a pit and light a fire in it. He then shot each of the Zetas in the head and ordered the bodies thrown in the flaming pit, according to Valdez.

“He said, ‘I don’t want any bones to remain,’” Valdez testified.

Guzmán later ordered Valdez himself killed because he wrongly thought he was stealing money, but he was persuaded to drop the order, Valdez said. Valdez testified that he went on to pilot drug planes for the cartel.

Prosecutors have said they expect to wrap up their case on Monday. Guzmán’s lawyers will then have a chance to call their own witnesses. It is not yet clear whether Guzmán will testify himself.