US Attorney General John Ashcroft made the decision that it could not be proven that Karla Patricia Chavez Joya, 25, deliberately caused the deaths, Michael Shelby, US Attorney of the southern district of Texas, said in a statement on Monday.
The immigrants, who came illegally from Mexico, Central America and the Dominican Republic, died from suffocation and heat exhaustion on 14 May when more than 70 people were crammed into a tightly sealed truck driven from southern Texas towards Houston.
"Federal law requires the government to prove beyond a reasonable doubt that a defendant intended to cause the death of a victim before the death penalty may be imposed," Shelby said. We have determined that such proof is presently unavailable."
He said four other people accused of helping Chavez and now in custody also would not be subject to the death penalty, but a decision was pending in the case of Tyrone Williams.
Prosecutors say Williams drove the smugglers' truck, but
abandoned it in Victoria, Texas, after seeing that the immigrants were dead or dying.
Chavez, a Honduras native who lived in southern Texas and
is in federal custody in Houston, has been called by prosecutors the "central cog" of a smuggling ring that brought
immigrants into the United States illegally for fees of up to
She and the others in custody are set to go to trial in a federal court in Houston in June.