A woman who rode in the cab of a truck during the deadliest human smuggling attempt in the United States tearfully testified Friday that the driver ignored her pleas to free the illegal immigrants crammed in the back of his sweltering trailer.

The driver, Tyrone Williams, is on trial for his role in the 2003 smuggling attempt in which 19 immigrants died. Williams did not respond to her pleading even as the immigrants pounded on the walls of the trailer, Fatima Holloway testified.

"I know they wanted out because they kept banging," said Holloway, crying as she spoke. "I figured it was hot back there. 'Let them out,' I said. At first (Williams) wasn't saying anything. He kept driving."

Holloway, one of the prosecution's key witnesses, told jurors at Williams' retrial how she got caught up in the smuggling attempt from South Texas to Houston.

Holloway, 31, who has pleaded guilty in the case and is out on bond, said her ex-boyfriend paid her to accompany Williams from Cleveland, Ohio, to a drug deal in Houston.

After meeting with several members of the smuggling ring, Williams drove his tractor-trailer to a secluded field near Harlingen, where more than 70 immigrants were loaded into the back.

Holloway said she heard the immigrants banging on the walls after the vehicle passed through a Border Patrol checkpoint in Sarita, about 75 miles north of Harlingen.

The trailer's temperatures quickly skyrocketed, but Holloway said Williams didn't turn on his trailer's refrigeration unit, which would have lowered the deadly heat. The immigrants peeled off their clothes and punched holes through the back lights for air as their body temperatures rose to as high as 113 degrees Fahrenheit.

After another tractor-trailer signaled Williams that something was wrong with his lights, he pulled over and discovered the holes, Holloway testified.

Williams eventually abandoned the trailer at a truck stop near Victoria, about 100 miles southwest of Houston. Seventeen immigrants were found dead. Two died later. They died from dehydration, overheating and suffocation.

Williams' lawyers contend he was unaware the immigrants were suffering.

A jury convicted Williams last year on 38 transporting counts, but he avoided a death sentence because the jury couldn't agree on his role.

Williams, 35, a Jamaican citizen who lived in Schenectady, New York, is the only one of 14 people charged in the case who is facing the death penalty.