Because of a missing witness, a judge on Monday rescheduled the capital murder trial of Alfredo Gomez, accused in the slaying of an FBI informant in a 2011 sting that turned into a shoot-out.
Prosecutors asked visiting judge Terry Flenniken to postpone Gomez's trial, which was expected to begin Monday, because a material witness could not be found.
Gomez, 21, and Ramirez, 37, each face an automatic sentence of life in prison if convicted of capital murder.
Chapa was working as a government informant when he was killed in a shoot-out while driving an 18-wheeler full of marijuana.
He was killed when three SUVs full of Zetas cartel gunmen opened fire on the tractor trailer in northwest Harris County.
In the ensuing violence, a Houston police officer shot an undercover Harris County sheriff's deputy in the leg. Authorities blamed the shooting on a lack of communication between the agencies.
The deputy recovered from the injury.