HOUSTON, (By Ralph Blumental, NYTimes) March 9, 2004 - The driver of the sealed truck that carried 19 illegal immigrants to grisly deaths nearly two years ago in South Texas in the nation's worst human smuggling disaster went on trial for his life here Tuesday with the government and the defense offering the jury sharply different pictures of his culpability.

In his opening statement, an assistant United States attorney portrayed the driver, Tyrone M. Williams, 34, a Jamaican from Schenectady, N.Y., as "the most heartless, evil and cruel" member of "a criminal enterprise that treated people worse than animals on their way to the slaughterhouse."

An admitted smuggling conspirator testified Tuesday that with the passengers suffocating and frantically punching holes into the uncooled refrigeration trailer, Mr. Williams called him angrily to complain: "How many people were back there? They're messing up my truck." He was motivated by greed, a $7,500 payment and the promise of more work, charged the lead prosecutor, Daniel C. Rodriguez.

Mr. Williams's lawyer, Craig Washington, conceded in his opening statement that his client was "guilty of transporting" the immigrants, but said that "every tragedy is not a crime" and that prosecutors "will not prove these poor helpless people died at his hands." Mr. Washington said that leaders of the smuggling plot were to blame for the 74 people packed into the 18-wheeler and that Mr. Williams, upon realizing their plight, rushed water to them. He also questioned why Mr. Williams, who is black, is the only defendant of the 14 charged in the plot to face the death penalty.

Mr. Williams, in a dark suit and tie and with his glasses at the end of his nose, sat between lawyers and listened impassively to the arguments and testimony. He is charged with 58 counts of transporting and causing injury and death to illegal immigrants.

The trailer, containing the bodies of a 5-year-old and 16 other people, was found abandoned near Victoria, Tex., on May 14, 2003. Many others were injured, including two who died a short time later. Mr. Williams, who had fled in the cab of the truck with a companion, was arrested later that day in a Houston hospital, where he had gone, he said, to seek treatment for shock and depression.

The investigation led to a ring that prosecutors said was headed by a Honduran woman, Karla Chávez, who organized safe houses on the Texas side of the Mexican border where illegal immigrants stayed until they could be smuggled past Border Patrol checkpoints and deeper into Texas. Ms. Chávez pleaded guilty last June to a charge that could send her to prison for life, but tried unsuccessfully in January to withdraw her plea.

Two others accused in the plot were convicted in Houston in December.

Mr. Williams's trial, which could last six to eight weeks, was repeatedly delayed over efforts by Mr. Washington to make the government explain why Mr. Williams alone faced capital punishment. The judge hearing the case, Vanessa D. Gilmore, ruled at one point that she expected to tell jurors in any punishment phase that the government had been resistant, but the decision was overturned by the United States Court of Appeals for the Fifth Circuit. The United States Supreme Court refused this week to review Mr. Williams's case, clearing the way for the trial before a jury of seven women and five men, three of them black.

With its first witnesses, the government sought to establish that Mr. Williams drove a refrigerated milk truck that could have cooled the passengers and saved their lives, and that he had previously smuggled a load of illegal immigrants without tragic results.

William Edward Idar, a supermarket clerk in Texas, testified that Mr. Williams delivered 1,445 cases of Lactaid milk to him from Oneida, N.Y., on May 9, 2003, and that the truck was refrigerated.

Another witness, Abelardo Flores Jr., who pleaded guilty and faces a life sentence as an organizer of the smuggling plot with Ms. Chávez, testified that at about the same time, he was trying to recruit truck drivers and chatted with Mr. Williams at a produce warehouse in McAllen, Tex. He was specifically looking for African-American and Caucasian truckers, excluding Hispanics because they draw too much suspicion at border checkpoints in the Rio Grande Valley, he said.

Mr. Williams was dubious and had to be encouraged, Mr. Flores, 36, testified. "He said he preferred drugs," Mr. Flores said, but ended up agreeing to carry a load of illegal immigrants through a Border Patrol checkpoint at Sarita on Highway 77 for $6,500.

At a brushy area outside Harlingen, while Mr. Williams sat in the driver's seat, his truck was loaded with 60 people, Mr. Flores testified. Mr. Flores said that the trip through the checkpoint went without incident and that he netted $16,000 after paying the driver and another person. He spent part of the profit on cocaine, he acknowledged.

A week or so later, Mr. Flores testified, Mr. Williams called seeking another job. This time, he said, Mr. Williams arrived with a companion, Fatima Holloway, who also pleaded guilty to a lesser role in the case and who was traveling with Mr. Williams, she said, to deliver drug money from Cleveland to San Antonio.

Mr. Flores testified that he put the two up at a motel in Harlingen, took them to dinner on May 13, 2003, and later that night led them to a wooded area where they picked up another load of illegal immigrants. He said that Mr. Williams demanded $7,500 and that he himself netted $11,500.

"I saw people running toward the trailer, the doors open," Mr. Flores said. He testified that Mr. Williams remained in the cab during the loading, but that he had not prevented him from getting out to look.

Mr. Flores said that he had been paid to load 60 people, but that Ms. Chávez had said 15 more were being added and would pay "if they made it."

Mr. Rodriguez, in his opening statement, said that Ms. Holloway, taken aback by the stampede of immigrants, voiced surprise, but that Mr. Williams responded: "Shut up. It's people. I know what I'm doing."

Mr. Flores testified that the immigrants expected a short ride through the Sarita checkpoint, but that the pickup truck and minivan that were supposed to meet them and carry them on had been stopped at the checkpoint. Mr. Williams agreed to take the immigrants to Houston for more money, Mr. Flores said. But in Victoria, after three and a half hours of driving, Mr. Williams became alarmed by signals from passing motorists, who saw holes being punched through the trailer by the desperate passengers, Mr. Flores said. Mr. Williams pulled over at a convenience store, and he and Ms. Holloway made four trips to take water to the immigrants.

Someone was crying, "El niño, el niño," the prosecutors and the defense agreed. But neither Mr. Williams nor Ms. Holloway spoke Spanish, they said, and did not know that the outcry was for a child, now dead.