He pleaded guilty to conspiring to harbor and transport aliens illegally in the United States resulting in death and serious bodily injury, the U.S. Attorney's Office said.
More than 70 immigrants were being transported to Houston from Harlingen in South Texas when the truck driver abandoned the trailer at a truck stop near Victoria, about 100 miles southwest of Houston, in 2003. The victims died of dehydration, overheating and suffocation.
Torres-Ortega faces life in prison and a maximum $250,000 fine. His sentencing is scheduled for Sept. 8.
"The horrific events of May 14, 2003, are by no means erased by today's final conviction," U.S. Attorney Don DeGabrielle said in a news release. "Though the sentencings of all, thus far, who were involved in the organized criminal enterprise should offer some measure of deterrence to any who consider making a living by smuggling human beings into this country."
Truck driver Tyrone Williams was sentenced to life in prison. He was the only defendant who faced a possible death sentence.
Other defendants have been convicted, pleaded guilty or won dismissal of charges. Those convicted have been sentenced to terms of up to 23 years in prison.